Science method

Analytical Chemistry - Science method

Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Qualitative analysis gives an indication of the identity of the chemical species in the sample and quantitative analysis determines the amount of one or more of these components.
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Which simulation software is best suited for comprehensive modeling and analysis of electrochemical systems?
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Electrochemistry Simulation Software | Ansys
ANSYS FLUENT 12.0 Fuel Cell Modules Manual - 3.5.1 Modeling Electrochemical Reactions
Electrochemical transport modelling and open-source simulation of pore-scale solid–liquid systems | Engineering with Computers
8th_OpenFOAM_Conference_Helmholtz_Zentrum_Weber.pdf
GitHub - pybamm-team/PyBaMM: Fast and flexible physics-based battery models in Python
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I am synthesizing nanoparticles at lab scale in small batches but I want to upscale the nanoparticles production. I studied that upscaling effects the size of nanoparticles such as stirring bar. Kindly help me if I want to upscale the same protocol e.g. from 100 mg starting precursor salt to 10 g precursor salt. How different parameters will effect the size and properties of nanoparticles?
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I hope this message finds you Noor Ul Ain well! Upscaling the production of nanoparticles can indeed be quite an adventure, and it’s fantastic to see you Noor Ul Ain considering the various factors that might influence your results. One crucial element to keep in mind is the size of the magnetic stirring bar, which can significantly impact the synthesis process by affecting mixing efficiency and reaction kinetics.
When scaling up, the size of the stirring bar should be proportional to the volume of your reaction mixture. A stirring bar that is too small may not generate the necessary turbulence for effective mixing, potentially leading to larger or poorly distributed nanoparticles. Additionally, increasing the stirring speed can enhance mixing and influence nucleation rates, which may result in smaller nanoparticles overall.
It’s also essential to pay attention to the concentration and volume of your reaction. Maintaining the correct concentration ratios is vital, as variations can affect supersaturation levels and subsequently impact nucleation and growth rates. Larger reaction volumes may necessitate adjustments in temperature control and stirring mechanics to replicate the conditions of smaller batches accurately.
Lastly, keep in mind that consistent temperature control becomes more challenging with larger batches. Uneven heating can lead to variations in nanoparticle size, and you Noor Ul Ain may need to monitor reaction times closely to ensure that the kinetics remain consistent when scaling up.
Each of these factors can significantly alter your experimental conditions, so I recommend documenting any changes you Noor Ul Ain make to better understand their impacts. Good luck with your experiments, and feel free to reach out if you Noor Ul Ain have any questions or need further insights!
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I have synthesized nanocomposite membrane for removal of heavy metals from wastewater as well as antibacterial activity also done. I have done lab scale experiment of adsorption studies. Now I want to move to bigger scale including making of fixed bed column and then RO plant filters. I need stepwise guidance how to scale up my nanocomposite membrane to making industrial scale filter. Following are my queries:
1- Should I start with fixed bed column? How many layers of nanocomposite membrane should be installed in a column?
2- Is peristaltic pump better or dosage pump?
3- My goal is to filter 6000 L of wastewater. Is RO plant better option?
4- Uptil now I have prepared nanocomposite membranes in lab in petri dishes. For bulk production should I consult some vendor to make it into a filter? And how many layers per filter?
5- Which equipment I actually need to build a column including glassware and their sizes?
Thanks in advance for your guidance.
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1. Fixed Bed Column Setup
Yes, a fixed bed column is an excellent intermediate step between lab-scale experiments and full industrial implementation. For your column:
  • Start with 3-5 layers of your nanocomposite membrane, monitoring pressure drop
  • Consider using a modular design that allows you to adjust the number of layers based on performance
  • Include sampling ports between layers to analyze removal efficiency at different depths
2. Pump Selection
For your application:
  • Peristaltic pumps are better for initial scale-up testing because they:Provide precise flow control Won't contaminate the fluid (fluid only contacts the tubing) Allow easy adjustment of flow rates Handle small particulates without clogging
Dosage pumps would be more suitable later for larger industrial applications.
3. Filtration System for 6000L
For treating 6000L of wastewater:
  • A hybrid system might be most effective
  • Start with your nanocomposite membrane filtration as pre-treatment
  • Follow with RO for final polishing
  • This combination would maximize heavy metal removal while optimizing energy usage
The decision depends on:
  • Required water quality standards
  • Types and concentrations of contaminants
  • Energy availability and operational costs
4. Bulk Production
For scaling up membrane production:
  • Consult specialized membrane manufacturing vendors who can adapt your formulation
  • Consider roll-to-roll manufacturing processes for continuous membrane production
  • Start with 5-7 layers per filter unit, adjusting based on pilot testing results
  • Work with the manufacturer to develop a quality control protocol to ensure consistency
5. Column Equipment Needs
For a pilot-scale column setup:
  • Glass column: 5-10 cm diameter, 50-100 cm height (borosilicate glass)
  • Column supports: Stainless steel or chemical-resistant polymer
  • Flow controllers and pressure gauges
  • Sampling ports at 10-15 cm intervals
  • Distribution plates at inlet and outlet
  • Backwash capability
  • Inline monitoring equipment (conductivity, pH, turbidity meters)
  • Collection tanks (feed and permeate)
  • Optional: automated data logging system
I recommend implementing a step-wise scale-up approach:
  1. Bench-scale column tests (1-5L)
  2. Pilot plant (50-500L/day)
  3. Demonstration plant (1000-5000L/day)
  4. Full-scale implementation
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This position is no longer available. Thank you for your interest.
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I am interested in this position and will be happy to share my CV.
Your prompt reply will be highly appreciated.
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When analyzing homologs using Thermo Fisher GC-MS (specifically, DB-5ms for TMS-derivatized dicarboxylic acids), full-scan mode works fine, but in selected ion monitoring mode, smaller molecules show no peaks while larger ones appear as expected.
I've confirmed that the retention times match between SIM and full scan, and the selected SIM fragments are the most intense in full-scan spectra.
What could be causing this, and how can I fix it?
Thanks in advance!
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The incorrect mass calibration of the quadrupole should raise this...Non-linear mass accuracy (FWHM) may cause biases in mass filtering. The full scan option transmits all to the EM detector (extended mass range selected for quad filtering. In SIM, single quad acts (if the ms-only mode is the case) a major role. Assuming you are not using the option of further fragmentation (MS/MS) there is a solution to verify this.
High masses and low masses are tuned for the quad and if your low mass calibration for the quad is less accurate than the high mass then the quad filters high mw well but low mw filtering will fail...This is more indispensable in SIM mode.
Tune your MS using a fresh/reliable calibrant and inspect the low masses in your tune solution through the tuning process in terms of monitoring the correct mass accuracy.
Setting the appropriate dwell times is also a good idea. You can also adjust the resolution in SIM mode acquisition a bit lower to enhance the sensitivity for small molecules.
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Hi, I am collecting RP-HPLC data using Shimadzu Labsolutions Version 5.71 SP1.
Every time I do the postrun PDA analysis, I have to manually remove unwanted peaks, e g. below retention time=4.5 min, etc. Basically, I am only interested in 3 peaks, at time=4.5, 6.5 and 11min. Besides, I need to copy the peak table one by one to my excel file for data processing and then graph plotting. It seems that I can only export each LCD data file into ASCII format one by one.
1) Is there anyway I can remove the unwanted all at once for all, say, 40 LCD data files, instead of editing it one by one in the software?
2) Is there any way to bulk export my data? The main purpose is just to ease data processing and cleaning, if it would.
3) Is there anyway to bulk export all forty chromatograms at once?
Thanks
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In Shimadzu LabSolutions Version 5.71 SP1, the terms "Processing Method" and "Batch Processing" may not appear explicitly in the menu, but the equivalent functions exist under Postrun Analysis and Data Analysis. Here’s where to find them:
1. Removing Unwanted Peaks in Bulk
Since LabSolutions doesn’t have a direct "Batch Processing" function, you can apply "Data Analysis Method" to multiple files:
1. Open LabSolutions Postrun
Go to [Postrun] in the software.
2. Set Up a Data Processing Method to Remove Unwanted Peaks
Open one chromatogram.
Click "PDA Data Processing" or "Quantitative Processing" (depending on your setup).
Go to "Peak Integration" and adjust parameters:
Set a retention time filter to only integrate peaks at 4.5, 6.5, and 11 min.
Save this as a New Processing Method.
3. Apply the Method to All Files at Once
In Postrun, go to File → Batch Processing Settings (or "Batch Recalculation" in some versions).
Select all 40 files and apply your saved processing method.
This will automatically remove unwanted peaks across all files.
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2. Bulk Export of Peak Table Data
LabSolutions does not allow exporting peak tables in bulk directly, but you can automate it:
1. Export Peak Table in ASCII Format (For Each File):
Open [Postrun] → [Peak Table].
Click "Export" → Choose ASCII (.txt) or CSV (.csv) format.
This needs to be done per file, but you can automate it with a script in Excel.
2. Automate Bulk Data Import into Excel:
Save all ASCII/CSV files in one folder.
In Excel, use Power Query (Data → Get Data → From Folder) to import all CSV files into one sheet for further processing.
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3. Bulk Export of Chromatograms
1. Export Multiple Chromatograms as Images/PDF at Once:
In Postrun Analysis, go to File → Export Chromatograms.
Select multiple files.
Choose output format (PDF, PNG, JPEG).
If this menu is not available, another workaround is to use "Batch Printing":
Go to Postrun → Print → Batch Print and save as PDFs instead of printing.
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We currently conducting a research study titled "Bioluminescent Bacteria Isolated from Squid Ink (Uroteuthis edulis) as a Biosensor for Detecting Dibutyl Phthalate." We are uncertain about the correct method for preparing a DBP stock solution using dimethyl sulfoxide (DMSO) as a solvent, and we want to ensure that the final concentration of DMSO does not negatively affect the bioluminescent bacteria. Below is the approach we have developed based on our research:   A stock solution of DBP (CAS No. 84-74-2; purity: ≥ 99%) will be prepared by dissolving DBP in DMSO to achieve a concentration of 1000 µg/mL (1 mg/mL). Some studies have used a final concentration of 1M. This stock solution will then be diluted with a sodium chloride solution (the medium for the bioluminescent bacteria) to obtain the desired DBP concentrations of 25, 50, 100, 400, and 500 µg/L. These concentrations were selected based on environmentally reported DBP levels ranging from 0 to 300 µg/L (Guo et al., 2016) and up to 500 µg/L (Fatoki & Ogunfowokan, 1993). We will also ensure that the final concentration of DMSO remains at 0.02% in all test solutions.   For each test, 50 µL of bacterial suspension will be mixed with 50 µL of the corresponding toxicant solution in a 96-well plate. DMSO will serve as the solvent and vehicle control, while zinc sulfate will be used as the positive control.  
Can you explain detailed preparation on making the final DMSO concentration (0.02%)
Should we follow the preparation guidelines from [this source](https://www.medchemexpress.com/Dibutyl_phthalate.html?srsltid=AfmBOooBHvDhMCM_JHk_IC8uHn1XMXTaI6vuoOCEBHDsedkLLeZ2WR_a), or would it be acceptable to follow other methods from previous studies?
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To ensure the final concentration of DMSO is 0.02%, you can start by calculating the total volume of your solution and adjusting the amount of DMSO accordingly. Here’s a step-by-step guide:
  1. Determine Total Volume and Concentration: Suppose you want to prepare a stock solution with a specific concentration of Dibutyl phthalate and a final DMSO concentration of 0.02%.
  2. Calculate DMSO Volume: 0.02% DMSO means 0.02 mL of DMSO in 100 mL of solution. For a smaller or larger volume, scale proportionally (e.g., for 10 mL solution, you'd use 0.002 mL DMSO).
  3. Dilute DBP in DMSO: First, dissolve the desired amount of Dibutyl phthalate in a small amount of DMSO. Then, dilute this concentrated mixture with a suitable solvent (e.g., water or buffer) to bring the DMSO content down to 0.02%.
  4. Verify Final Concentration: Carefully mix the solution and confirm the final DMSO concentration through calculations or tests.
let me infor whether it works or not ?
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Suppose you began your career in organic chemistry (MSc and PhD) but later specialized in analytical chemistry (Dr. Sci.) and conducted research in this field for over 15 years. How would you identify yourself?
1. As an organic chemist
2. As an analytical chemist
Reply by (1) or (2).
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(2)
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Hello,
I have encountered problems when it comes to making a dithizone solution. I intend to analyze environmental water samples for heavy metal concentrations ( As, Ca, Cd, Cu, Hg, and Pb) using Uv-vis and AA. I started off making a dithizone solution with 0.1g of dithizone and 250 mL of DI H2O along with 2g of SDS. This caused some of the dithizone to dissolve but it would just settle to the bottom of the volumetric flask. I also reduced the solute to 0.02g of dithizone with 2g of SDS in 250 mL of DI H2O. This allowed for more dissolving, but it again settled to the bottom of the volumetric flask. In addition, heat was applied at around 100 C with a magnetic stir bar and HNO3 was used to drop the pH of the solution, and it helped with dissolving the solution but went from a blue grey to a brown color. The reason why I used HNO3 was because the stocks the I had made from stock solutions had HNO3 in them and HNO3 was also added to my environmental water samples for preservation. I am avoiding using organics as a solvent due to having water samples and do not want it to affect my calibration curve. Any insights will be helpful.
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You are very welcome!
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I'm working on the method development for the analysis of various PPCPs and emerging contaminants in aquatic environments, currently focusing on SPE recovery by spiking compounds in Milli-Q water. Using the OASIS HLB cartridge, I’m achieving good recoveries for most compounds, but triclosan remains problematic. My method involves washing with 5% methanol in water and eluting with methanol. I've tested different pH levels (pH 2, 4, 7, 10) and various elution solvents (methanol, acidified methanol, basic methanol, methanol with ethyl acetate, and methanol with DCM), yet I haven't recovered triclosan. I even tried DCM, expecting it would help, but saw no improvement. I am now planning to collect samples at each SPE stage after sample loading to pinpoint where triclosan is being lost. I’m using nylon 0.2 filters with syringes and all glassware throughout the process, but I’m struggling to identify the cause of the issue. Could anyone share their thoughts on this? Thanks
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Dileep Singh Good to hear you found the problem.
When I develop methods for formulations where filtration is important, I usually screen at least two types of filter materials (such as nylon and PTFE) and two different manufactures for each (say, FischerSci and MilliporeSigma). Additionally, I would keep the diameter (for example, 33 mm for all, otherwise there will be difference in binding and filtration capacity due to the surface area) and the material of construction for the housing the same (such as polypropylene; this is to avoid difference due to degradation and leeching, especially with aggressive solvents or base/acids). Whenever possible, I also use centrifugation as the reference solution to evaluate differences due to filtration. Since centrifugation is more straightforward, if I can get a clear solution where the expected recovery matches the experimental, that's my go to.
It's not unusual to see difference in results between labs when filtration is used. Some suggested reasons are listed below.
It's common to see a difference of a few percents in recovery using the same filter material from different manufacturers (especially if the diameters are also different).
If standard syringe filtration is used, that's prone to user variations:
- One point of variation for example is: I often prefer to discard the first few drops of filtrate as it may contain leechables or particles from the filter and/or syringe. But sometimes there is insufficient starting solution to sacrifice this amount.
- Another variation may be the final step of the filtration: Some people push the syringe plunger all the way in, thus trying to collect every last drop from the filter. This allows collecting of all volume and material but also may rupture the filter or create bubbles (and with that aggregates when we work with polymeric substances); it may also force out particles that would otherwise be retained by the filter.
- The total sample load( concentration and volume) and turbidity of the solution is important. If you only had one analyte in a clear solution, then that would filter more efficiently that filtering a solution that contains 10 analytes + matrix additives that is also turbid. The filter would then quickly exceed its binding capacity and may leave no pores for the analytes that would normally pass to traverse through the membrane.
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Hi,
I am calculating the N/P ratio to encapsulate dsDNA into a LNP. I am using two different methods, but obtaining a worrying difference in the result. I believe it could be a mistake in one of my calculations but not sure which.
1st Calculation - Using atomic count of N to P ratio
My mixture has 0.0075M of Lipid x 0.001L x 6.022x1023 = 4.5x1018 Ns (considering one N per lipid molecule)
N/P ratio of 4/1 so I need 1.125x1018 Phosphates (4.5x1018/4). My DNA is 7000bp long and therefore has 14000 phosphates, so dividing the Nº of Phosphates needed by the Nº of phosphates I have per DNA molecule (1.125x1018/14000) equals 8.03x1013 of DNA molecules needed. I can then easily calculate the DNA mass (DNA molecules needed x MW of 7000bp DNA)/6.022x1023
This equals 618ug of DNA
2nd Calculation - Using a mol/mol N/P ratio.
Molecular Weight of my lipid is 620.09g/mol and I am adding 4.65ug so dividing 4.65x10-6 g ÷ 620.09g/mol) I get 7.5x10-9 mols of N used, since there is 1 mol of N per mol of lipid.
N/P ratio 4/1 so I need 1.88x10-9 moles of Phosphate. There are approx. 3x10-9 moles of phosphate per ug of DNA so dividing the moles of phosphate I want by what I have (1.88x10-9moles ÷ 3x10-9 moles/ug)
This equals 0.626ug of DNA
Surely there is a mistake I am not seeing, any help will be greatly appreciated.
Thanks!!!
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Hello.
If I see it correctly, the amount of lipid you add differs by a factor of 1000 between both calculations. In calculation 1, it's only 7.5^(-6) mols. However, apart from the decimal power, the numbers are very similar which is why I guess, there are rounding errors. The true result should be 0.625 ug (or mg) as you can see in the photo attached.
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I'm currently working on calculating the collision cross section (CCS) for various ions, and I'm facing challenges when dealing with sodiated and multiply charged ions.
Most of the resources I’ve found focus on protonated or deprotonated forms, but I need to calculate CCS for:
  1. Sodiated Ions: What adjustments or considerations are necessary to accurately calculate CCS for sodiated ions?
  2. Multiply Charged Ions: What are the best practices or computational methods for handling the complexities of CCS calculations in multiply charged ions?
I would greatly appreciate any advice, recommended tools, or literature that could guide me in this process.
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Calculating the collision cross-section (CCS) for sodiated adduct ions and multiply charged ions involves experimental and theoretical approaches. Here's how to proceed:
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1. Experimental Approach (Using Ion Mobility Spectrometry - IMS)
Sodiated adduct ions ([M+Na]⁺) and multiply charged ions (e.g., [M+2H]²⁺) are injected into the IMS instrument.
Measure the drift time () under a known electric field, gas type (e.g., N₂ or He), pressure, and temperature.
Use the Mason-Schamp equation to calculate CCS ():
\Omega = \frac{{3ze}}{{16N}} \left( \frac{{2\pi}}{{k_BT\mu}} \right)^{1/2} \frac{{t_dE}}{{L}}
Where:
: Charge of the ion.
: Elementary charge.
: Gas number density.
: Boltzmann constant.
: Temperature.
: Reduced mass of the ion-gas pair.
: Drift time.
: Electric field strength.
: Drift tube length.
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2. Theoretical Approach (Trajectory Method)
For sodiated or multiply charged ions:
Generate 3D structures of the ions using computational methods like density functional theory (DFT).
Simulate ion-neutral interactions using programs like MOBCAL or IMoS to estimate CCS based on ion dynamics.
Account for the effects of sodium addition or multiple charges on the ion's structure and interaction with drift gas.
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Key Considerations:
Multiply Charged Ions: CCS typically decreases with increasing charge due to compaction from Coulombic interactions.
Sodiated Adduct Ions: The CCS may increase slightly due to the larger ionic radius of sodium.
Use accurate experimental conditions and computational models to ensure precision in CCS calculations.
Let me know if you need specific software recommendations or detailed examples!
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Hello Dears,
I use ferrous sulfate as a chromium reducer. As we know from the chemical reaction equation 3 mol Ferrous reacts with 1 mol of cr(vi) which means 3.22 mg ferrous reacts with 1 mg of cr(vi), am I right ?. the sample contains 5.28 ppm cr(vi), how much reducer(by mass ) should be added to 1 kg of sample to reduce the amount of cr(vi) by 1 ppm ??
suppose the purity of the reducer is 100%.
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To calculate the amount of chromium reducer, let’s assume:
1. Sample volume = 1 liter (1000 mL).
2. Cr(VI) concentration = 5.28 ppm = 5.28 mg/L.
3. Reducer: Sodium bisulfite (NaHSO₃), which reacts with Cr(VI) in a 3:1 molar ratio:
3NaHSO₃ + 2CrO_4^{2-} + 4H^+ \rightarrow 3NaHSO_4 + 2Cr^{3+} + 2H_2O
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Step 1: Moles of Cr(VI)
Molar mass of Cr = 52 g/mol
Mass of Cr(VI) in 1 L sample:
5.28 \, \text{mg} = 0.00528 \, \text{g}
\text{Moles of Cr(VI)} = \frac{0.00528}{52} = 0.0001015 \, \text{mol}
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Step 2: Moles of Sodium Bisulfite (NaHSO₃)
From the reaction stoichiometry, 3 moles of NaHSO₃ are required per 2 moles of Cr(VI):
\text{Moles of NaHSO₃} = \frac{3}{2} \times 0.0001015 = 0.0001523 \, \text{mol}
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Step 3: Mass of Sodium Bisulfite (NaHSO₃)
Molar mass of NaHSO₃ = 104.06 g/mol
Mass of NaHSO₃ needed:
\text{Mass} = 0.0001523 \times 104.06 = 0.01584 \, \text{g} = 15.84 \, \text{mg}
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Final Answer:
You need 15.84 mg of sodium bisulfite to reduce 5.28 ppm of Cr(VI) in 1 liter of the sample. Adjust proportionally for different sample volumes.
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Hallo,
I have a glucose syrup with sugar, I wann to mix them with heating up to 115 c. Then I have to cool it until 95 c and add another mix with stable temp. I use for that purpose a hot plate. My question is: how to control the temp of the mixture at 95 c during this process? Taking in our consideration that 95 c is the temp of the liquid not the surface of the hot plate.
Thanks in advance
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The best control is often inertia! Use your hot plate - preferably one with automatic temperature sensing by a probe in a large beaker of water - to maintain a water bath at 95'C. That should be fairly easy to control and pretty accurate. Then you put your syrup mixture into a vessel immersed in the water bath. Final feedback of a temperature probe in your solution mixture will let you know when the entire solution is at the equilibrium temperature of 95'C. The initial temperature of your mixture or additive and the rate of addition to the mixture will determine how much localized temperature variation you will have. Slower is more homogeneous.
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How to calculate Tow one-sided t-tests with intersite (receiving & transferring)differences ≤ 10%,95% confidence for residual solvents by GC - HSS (n=8, 4 for receiving and 4 for transferring sites) for analytical method transfer. Whether this t-test mentioned in the guidelines referes to Schuirmanns TOST.
if so, whether the ≤ 10%, spceification is upper and lower limit.
results were failying w.r.to GC OVI analysis hence the % SD is about 25% for one side and about 10.5 for the other side. as per the guidelines we have presumed that one side n=4, hence performed the TOST taking n=8.
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Can you help answer how to calculate this ? I am getting stuck in this dilemma.
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I received my PhD in Analytical Chemistry, am I eligible for this position?
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Based on your analytical skill with branch you can apply.
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I fabricated microbeads using hydrogel (20-50 micrometres) to mimic human cells' size and mechanical properties; I want to stain them to be able to recognize them under an optical microscope. Which staining should I use? I don't have confocal microscopy at the moment, so I think fluorescence inks will not be helpful here; I am using the microscopic camera to view those beads
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Try gram staining of microorganisms and you can also distinguish them buy once.
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A renowned professor recently posed this question, and I don't have an answer. Could anyone provide insight? Why don't we use water as the extractant to directly measure available nutrients in soil for analysis, instead of relying on more complex chemical solutions?
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Plants exude various organic acids from their roots that are used to solubilize mineral nutrients from the soil matrix. Microbes exploit the root exudates while also produce siderophores and their own organic compounds that can preferentially bind nutrients, all of which form a "rhizosphere" within the soil, altering pH and nutrient availability to the benefit of the plant.
If only "water soluble" nutrients are considered, the full complexity of the soil-plant-microbe-atmosphere ecosystem is reduced to a very small subset.
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I read some old questions where people said you can change that on the settings tab in your profile. But there is nothing about research interests or anything like it. Is there a way I can change? I published an article on analytical chemistry but I also like pharmacology and I'd like to see novel published articles of this matter.
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In short, Yes, you can change your research interests. Identify what excites you now and how it aligns with your goals...Discuss your new interests with your academic advisor or mentor for guidance and to understand how it might affect your current work...Read up on your new area to gain a deeper understanding and identify gaps or questions that you’re passionate about...
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Dear Experts,
kindly suggest me a best method to estimate the percentage of potassium sulphate in the organic fertilizers.
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Karuppiah Valliappan To estimate potassium sulfate (K2SO4) in organic fertilizers, you can use the following methods:
1. Spectrophotometry: Measure the absorbance of a sample solution at a specific wavelength (typically 420-440 nm) using a spectrophotometer.
2. Atomic Absorption Spectroscopy (AAS): Measure the absorption of light by potassium atoms in the sample.
3. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES): Measure the emission spectra of potassium ions in the sample.
4. Titration: React the sample with a strong acid (e.g., HCl) and measure the volume of acid required to neutralize the potassium sulfate.
5. Gravimetry: Precipitate potassium sulfate as potassium tetraphenylborate and measure the weight of the precipitate.
6. Ion Chromatography (IC): Separate and measure the potassium and sulfate ions in the sample using an ion chromatograph.
7. Near-Infrared Reflectance Spectroscopy (NIRS): Measure the reflectance of the sample at specific wavelengths to estimate potassium sulfate content.
These methods may require sample preparation, such as drying, grinding, or dissolving the organic fertilizer in a solvent. To ensure accurate results, it's essential to follow standardized protocols and calibration procedures.
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I dissolved the 5 Kg of sample in 40 liters of water and left it for 24 hours. Then I used a pump to collect the supernatant liquid without disturbing the sediment and then filtered it for any impurities.
I repeatedly evaporated half of the water(40->20->10->5) and decanted the solution after sedimentation with the help of a transfer pump four times. After that, with further evaporation followed by sedimentation, some grainy crystals of salt(table salt size) were formed, and the supernatant liquid was removed with the help of a pipette (filtration could not be done due to the viscosity of the solution). I found that this salt was KCl and it was present in good amount in the solution (though there could be other salts too) which made the resin salty (but the resin tastes bitter, not salty). In the end, I evaporated most of the water and kept the solution for 12 hours, small grainy crystals(smaller than table salt size) of KCl formed in the solution, and the consistency of the solution was such that the solution could flow slowly. Then I centrifuged the solution for 10 minutes at 1200 rpm in a 50 ml tube and found that the viscosity of the solution was low at the top and increased up to 15ml mark in the tube, after that the semi-hard settled salt present in the bottom of the tube. but the taste of the solution is still salty.
Is there any method by which we can completely remove the salt from the resin ?
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What is the general mechanism of Schiff bases reaction for determination of drug in analytical chemistry ?
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Hi, I am a PhD student working at Jagiellonian University, Faculty of Chemistry. My work is related to the development of new analytical methods for the quantification of short-chain fatty acids in biological samples. In my research, I used a gas chromatograph (Shimadzu GC-2030 Nexis) coupled with a triple quadrupole mass spectrometer (Shimadzu TQ-8040). I developed a new GC-MS/MS method for the quantification of short-chain fatty acids, but I have a problem with the carry-over effect. After injection of high concentrations of analytes, such as 10 ug/ml, I observed peaks from the analytes in the blank sample. The problem is a little bit reduced when I frequently change the solvents (water and ethanol) and utilize a long washing procedure after injection, but it still exists. The current washing procedure includes 4x8µl H2O, 4x8µl EtOH, and 4x8µl EtOH. In addition, sequence – 20x8µl H2O, 20x8µl EtOH, and 20x8µl EtOH were utilized for extra washing following the analytes with the highest concentration.
Do you have some experience with the carry-over effect in the GC-MS/MS system and some suggestions to solve my problem?
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Syringe wash is not the only approach to clean Your system. If You inject "dirty" samples the whole injector (including tubing) might get dirty. A solvent injection between the samples should will help in most cases....... If there are ghost peaks it might help to prolong the GC program.
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Hi,
Just curious to know that in chromatography, a chromatogram should be zoomed to what scale? 10 times of output , 50X or ..? Is there any regulation or general chapter which describes this? Does it varies from lab to lab & test to test?
Thank you for your guidance.
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There is no single universal rule, following regulatory guidance and best practices for chromatogram scaling can help ensure the data is clear, informative, and suitable for its intended purpose. The specific scale should be determined based on the analytical requirements and adjusted as needed to maintain data quality.
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International Conference on Engineering, Science, Technology, and Innovation (IESTI 2024)
Date: 19-09-2024
Location: Online
Submission Deadline: 15-07-2024**** Extended to 1-8-2024
The Organizing Committee of the International Conference on Engineering, Science, Technology, and Innovation (IESTI 2024) is pleased to invite researchers, practitioners, and professionals to submit papers for presentation and publication at the IESTI conference. This prestigious event aims to bring together leading scholars, researchers, and industry experts to exchange and share their experiences and research results on all aspects of Engineering, Science, Technology, and Innovation.
Topics of Interest
Topics of interest for submission include, but are not limited to:
  • Engineering:
    • Mechanical Engineering
    • Electrical and Electronics Engineering
    • Civil Engineering
    • Chemical Engineering
    • Aerospace Engineering
    • Materials Science and Engineering
    • Computer Science and Engineering
  • Science:
    • Physical Sciences
    • Life Sciences
    • Environmental Sciences
    • Earth Sciences
    • Chemical Sciences
    • Artificial Intelligence
  • Technology:
    • Information Technology
    • Communications Technology
    • Nanotechnology
    • Biotechnology
  • Innovation:
    • Technological Innovation
    • Innovation Management
    • Entrepreneurship
    • Sustainable Development
    • Policy and Innovation
Submission Guidelines
Authors are invited to submit original, unpublished research papers that are not currently under review elsewhere. All submissions will be peer-reviewed and evaluated based on originality, technical and research content, correctness, relevance to the conference, contributions, and readability.
Paper Submission Process:
1. Format: All papers must be formatted according to the conference template available on the conference website.
2. Length: Full papers should be between 6-10 pages, including all figures, tables, and references.
3. Submission Link: Submit your papers through the online submission system available on the conference website.
4. Review Process: Each paper will undergo a blind peer review process.
5. Notification: Authors will be notified of the review results by 15-08-2024.
6. Camera-Ready Submission: Final versions of accepted papers must be submitted by 31-08-2024.
Important Dates
  • Paper Submission Deadline: 15-07-2024 **** Extended to 1-8-2024
  • Notification of Acceptance: 15-08-2024
  • Camera-Ready Paper Submission: 31-08-2024
  • Early Bird Registration Deadline: 20-08-2024
  • Conference Dates: 19-09-2024
Conference Proceedings
All accepted and presented papers will be published in the journals listed on the following website:
Special Sessions and Workshops
  • IESTI 2024 will also feature special sessions and workshops focusing on current trends and emerging topics in Engineering, Science, Technology, and Innovation. Proposals for special sessions and workshops can be submitted to editor@academicedgepub.co.uk, by 1-8-2024.
Contact Information
For any inquiries regarding paper submissions or the conference, please contact:
We look forward to your participation in IESTI 2024 and to a successful conference!
We would like to extend our invitation to invite you to join the editorial board of the:
- Journal of Probiotics and Bioactive Molecules Research (JPBMR)
Please send an email including your full name, affiliation, CV, and mention the selected journal to the following email address: editor@academicedgepub.co.uk
Sincerely,
IESTI 2024 Organizing Committee
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Looking forward to seeing this all progress
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What is the difference between reaction and interaction in chemistry? Would you please provide me with the details?
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Dear Doctor
[Interaction:
The situation or occurrence in which two or more objects or events act upon one another to produce a new effect; the effect resulting from such a situation or occurrence.
Reaction:
An action or statement in response to a stimulus or other event.]
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What is the difference between absorption and adsorption?
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The main difference is that while absorption involves the mass transfer of particles into another material (one substance absorbing another), adsorption takes place with the adhesion of particles onto the surface of a substance. absorption is the process in which a fluid dissolves by a liquid or a solid. In the case of Adsorption, the atoms, ions, or molecules from a substance adhere to a surface of the adsorbent
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Hello,
I have a methanol extract that I have let stand for 3 days, three times. I have evaporated the methanol and, just to be sure, mixed it with water and lyophilized it. Before performing HPLC, I want to remove nonpolar impurities, chlorophyll, and pigments from my extract using liquid-liquid extraction to prevent damage to the C18 column. My first question is: should I use ethyl acetate, chloroform, or hexane for this purpose?
For one of my samples, I washed it three times with ethyl acetate and even left it shaking overnight. For another sample, I sonicated it. The sonicated sample changed color, and the water volume of all my samples increased by about 10-15%. How can I remove the ethyl acetate, and would using the extract in this state without removal damage the C18 column during HPLC analysis?
Thank you.
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Generally speaking,to remove nonpolar impurities from a methanol extract, you would typically use a solvent that is immiscible with methanol and has a higher affinity for the nonpolar compounds. One common solvent for this purpose is a nonpolar organic solvent like diethyl ether or hexane...Remember to handle all solvents with care and follow proper safety precautions, including working in a well-ventilated area and avoiding contact with skin or inhalation of vapors. Additionally, ensure that the selected solvent is compatible with your compounds of interest and that it does not introduce any unwanted impurities.
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Dears,
I'm using the UV/vis method to determine water-soluble chrome in cement as follows:
I take particulate mass from dichromate to make a stock solution then take various volumes of aliquots into a 50 ml volumetric flask to set up a calibration curve.
for measuring the sample, I take a 25 g sample and 25 ml of water then filter and take 5 ml of filtrate into a 50 ml volumetric flask and dilute to mark with water after adding a color indicator.
my inquiry why don't I consider 50 ml dilution of aliquoted sample in the calculation equation ? and if I deviate from the method and make a dilution of the aliquoted sample 100 ml instead of 50 ml what does the formal calculation equation become?
#analytical Chemistry
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- Why don't I consider 50 ml dilution of aliquoted sample in the calculation equation ?
Because you are diluting both, sample and standard, to the same final volume of 50 mL.
If you decide to dilute your sample to 100 mL instead of 50 mL, this means that the concentration value that you will get from the calibration curve must be multiplied by a factor of 2 (because the sample is now twice more diluted than the standards).
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Can a published journal article be submitted to conferences?
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It is quite common to present talks or posters on the basis of previously published papers. However, care must be taken when contributing to the proceedings of the conference so as not to infringe the copyright of the journal's publisher.
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For those working in the field of Mass Spectrometry, Chromatography and allied topics, and based in NY state, we are launching a new local discussion group !
Feel free to sign up as member to be part of it.
We will organize in-person events (main area: Buffalo, Syracuse, Ithaca, Corning, Rochester) and virtual meetings - which anybody can attend !
Soon to be listed officially among other local discussion groups on the American Society for Mass Spectrometry (ASMS) website.
Thierry
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ahah hello All !
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After performing boehm titration using HCl,NaOH, Na2CO3, and NaHCO3.  I want to know the formula to calculate functional groups.
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Dear Esteemed Colleague,
Greetings. I trust this message finds you well and thriving in your scientific pursuits, particularly in the area of surface chemistry and characterization. Your inquiry about the mathematical formula for calculating functional groups on surfaces such as carbon materials via Boehm titration is both important and insightful. The Boehm titration technique is a cornerstone in the quantitative analysis of acidic and basic surface functional groups, providing invaluable data for material scientists and chemists alike. Below, I provide a detailed exposition on the formulation and methodology for calculating the concentration of these functional groups using Boehm titration.
Overview of Boehm Titration
Boehm titration is a technique designed to quantify the acidic and basic functional groups present on the surface of carbonaceous materials. This method involves treating the sample with a series of bases and acids to neutralize acidic and basic sites, respectively. The quantity of acid or base that reacts with the sample surface groups is then measured, providing an estimate of the functional group content.
Mathematical Formulation
To calculate the concentration of surface functional groups, the following formula is commonly employed:
�=(�blank−�sample)×��C=m(Vblank​−Vsample​)×N
where:
  • C is the concentration of functional groups (mol/g),
  • �blankVblank​ is the volume (in L) of titrant used in the blank titration,
  • �sampleVsample​ is the volume (in L) of titrant used in the sample titration,
  • N is the normality of the titrant, and
  • m is the mass (in g) of the carbon sample.
Step-by-Step Calculation
  1. Perform Titration:Carry out the titration for both your sample and a blank. The blank titration helps account for any titrant that does not react with the sample but is consumed due to other factors (e.g., dilution).
  2. Measure Volumes:Accurately measure the volumes of titrant used in the blank and sample titrations.
  3. Determine Normality:Ensure the normality of the titrant is accurately known. This may involve standardizing your titrant against a primary standard.
  4. Calculate Concentration:Use the formula provided to calculate the concentration of functional groups on the surface of your material.
Considerations and Best Practices
  • Accuracy of Measurements: Precision in measuring the volumes of titrant and the mass of the sample is critical for reliable results.
  • Selection of Titrants: Choose appropriate acids and bases for titration, typically hydrochloric acid for basic sites and sodium hydroxide, sodium carbonate, and sodium bicarbonate for various acidic sites.
  • Replicates and Averages: To ensure reliability, perform multiple titrations for both the sample and blank, averaging the results for increased accuracy.
  • Correction for Blank: Always subtract the volume used in the blank titration from that used in the sample titration to correct for non-specific consumption of the titrant.
By adhering to these guidelines and employing the formula with diligence, you can accurately quantify the functional groups present on the surface of carbon materials via Boehm titration. This quantification is essential for understanding the chemical behavior and potential applications of these materials.
Should you require further clarification or wish to explore more about the application of Boehm titration in material science, please do not hesitate to reach out. Your dedication to advancing our understanding of material surfaces is commendable, and I am here to support your research endeavors.
Warm regards.
Check out this protocol list; it might provide additional insights for resolving the issue.
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I am measuring primary aromatic amines by UV-VIS and using the NEDA solution as my coupling reagent. The method says that the reagent needs to be made fresh every day. However, the solution is sold commercially from 0.1-1.0% with a shelf life of 6-12 months. Why does it have to be made fresh? What is its stability? Is it a temperature or UV dependent reaction? Can storing in a brown(amber) bottle and/or refrigerating allow for longer use?
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In such cases, it is preferable to prepare it daily and avoid its instability as a result of it being affected by various conditions such as light, temperature, etc. It is best to prepare the amount as needed daily
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Dear colleagues,
We have recently optimized a TDS-GC-MS method for VOCs (SVOCs) analysis. (Gerstel + Agilent).
A high-temperature column with mid-polarity is chosen for a better resolution (similar to DB-624ms but with a higher operating temperature of 300/320 °C).
Although the desired separation is achieved with a programmed-temperature method (final temperature: 290 °C), some analytes with low boiling points, such as dichloromethane, benzene, and heptane, show unacceptable intensity variation. (The RSD of three replicas can be as high as 30%). On the other hand, compounds with higher boiling points (such as naphthalene and pentadecane) are more stable. (RSD < 5%)
We further lower the final temperature of the method (from 280 °C to 260 °C), and the repeatability of benzene and heptane is much better (RSD < 5%), while the dichloromethane is still fluctuating (RSD ~ 15%).
Any explanation for this phenomenon?
p.s. the column pressure can be very high under high-temperature
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Hey there Junlong Huang,
It's great to hear about your progress with the TDS-GC-MS method for VOCs analysis! Now, regarding your question about the final oven temperature and its influence on the repeatability of low boiling point analytes, let's dive into it.
The fluctuations in intensity you're observing, particularly with dichloromethane, benzene, and heptane, can indeed be puzzling. The change in final oven temperature seems to have a significant impact on the stability of these compounds, with lower temperatures showing better repeatability for benzene and heptane but not so much for dichloromethane.
One potential explanation for this could be the volatility and thermal stability of the compounds. Lower boiling point analytes like dichloromethane are more sensitive to temperature changes, and even a slight variation in final oven temperature can lead to fluctuations in their intensity. On the other hand, compounds with higher boiling points like naphthalene and pentadecane are less affected by these temperature changes, hence the more stable RSD.
Additionally, considering the column pressure under high-temperature conditions is crucial. High pressures can exacerbate the volatility of low boiling point analytes, leading to increased intensity variation.
In summary, the interplay between compound volatility, thermal stability, and column pressure under high-temperature conditions likely contributes to the observed phenomenon. Fine-tuning the method parameters, such as oven temperature and column pressure, can potentially mitigate these fluctuations and improve repeatability.
Hope this sheds some light on the issue! Let me know if you Junlong Huang need further clarification or assistance.
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In 2009, while investigating whether injections of methylcobalamin would help my chronic health condition, I chanced upon an intriguing happenstance. The contents of four vials (from a batch of twelve vials) were remarkably effective. All up, over a two-year period I injected methylcobalamin from a total of 41 vials (from four different batches). Injections from 37 of the vials made no impact whatsoever on my condition. Injections from the four effective vials were not consecutive so this wasn't a situation where an initial good response waned.
From the batch of twelve vials that contained four effective vials, the first two effective vials were discarded after use. I saved the remaining ten used vials.
In early 2012 I had the dregs from the ten vials analysed (HPLC at 361 nm). Unfortunately I could not distinguish the two effective vials from the other eight vials so the best I could achieve was to discover if there was anything different about two of the ten vials.
A methylcobalamin injection in light-protected glass ampoule from a different manufacturer was used as the standard (i.e. Methycobal® made by Eisai Co Japan).
Along with the dregs from ten used vials, content from an unused but expired vial (which had been stored correctly) and content from an unused but current vial (sent directly to the analytic lab from the manufacturer's premises) were analysed.
HPLC indicated the standard (i.e. Methycobal®) was pure. It contained two major peaks, the main being MeCbl (eluted at ~ 19 mins) with a smaller OHCbl peak (eluted at ~ 13 mins). Identity of these peaks was subsequently confirmed by MS.
HPLC of the remaining 12 samples (10 x dregs from used vials + 1 x expired vial + 1 x current vial) indicated all were similar to each other. All 12 samples contained four major peaks. Two of these major peaks corresponded to the two peaks in the standard (i.e. MeCbl + OHCbl). Relative ratios of these peaks was as expected – i.e. more MeCbl had degraded to OHCbl according to age of product.
All vials contained significantly more MeCbl than OHCbl (gauged visually from height/width of peaks and subsequently confirmed by calculation of area under peak).
The lab is a reputable commercial lab with up-to-date equipment.
The results look 'pristine'.
All major peaks are symmetrical, narrow, distinct, well separated, no tailing, twin peaks etc.
The lab ran blanks before and between samples.
The order of run was –
10 x dregs* > 1 x expired vial > 1 x standard (Methycobal®) > 1 x current vial
* The first 4 x dregs were rerun the following morning (approx 20 hrs later) because operator was not happy with initial results (I think there was rt drift)
Additional listed ingredients do not account for the unidentified peaks.
Additional listed ingredients –
• Methycobal® – D-mannitol 50 mg (per 500μg MeCbl in 1mL ampoule)
• The vials – Sodium Chloride 18 mg (per 10,000 μg MeCbl in 2mL vial)
Neither product contains preservative.
Concentration of the samples for analysis made from the dregs varied due to variable volume of dregs in each vial.
Looking at the HPLC chromatogram –
Visually it is obvious that two of the ten vials with dregs contain significantly more of one of the two unidentified major peaks (eluted at ~ 15 mins). Relative to the height of the MeCbl peak this peak is ¼ to ⅓ MeCbl height in 8 x dregs. In 2 x dregs it is around ½ the height (i.e. there is around twice as much of this substance in 2 x dregs than in the other 8 x dregs).
I used the height (mAU) of the MeCbl peak to plot a standardised graph of the height of the peaks in Excel. That is, I multiplied the mAU for the MeCbl peak of each sample by a factor^ so that MeCbl peaks from each sample were equal – i.e.they appear as a single dot on the Excel graph. (In the chromatogram the mAU of the MeCbl peak for the standard + expired and current vials was similar but the mAU for the dregs varied due to limited volume available for analysis.)
^ For each sample, mAU of each major peak was raised by the same factor (i.e. factor needed to equalise MeCbl).
When plotted in Excel the results look orderly. The unidentified peak at 15 mins is more or less the same height as the OHCbl peak for all samples except for 2 x dregs. The unidentified peak at ~ 12 mins is a little lower than the OHCbl peak in all samples. (These two peaks are missing from the standard.)
The OHCbl peak is lowest in the current vial and in the standard – I'll call this the baseline. OHCbl peak is approx 70% higher than baseline in expired vial and in 6 x dregs (in 4 x dregs OHCbl is ~ 55% higher than baseline).
The unidentified peak at 12 mins is lowest in the current vial (baseline). It is around 70% higher in the expired vial, and higher still in the 10 x dregs (varies from 130% to 250% higher than baseline, evenly distributed through this range).
The unidentified peak at 15 mins is lowest (baseline) in current and expired vials (around 20% higher in expired than in current vial). In 8 x dregs the height of this peak varies from 36% to 85% higher than baseline (evenly distributed through this range). In 2 x dregs the height of this peak is 200% to 220% higher than baseline.
The baseline for each peak:
~12 mins 175 mAU
~13 mins (OHCbl) 375 mAU
~15 mins 357 mAU
~19 mins (MeCbl) 2270 mAU
At the time of HPLC analysis the attitude from analytical lab and manufacturer of vials was that it was virtually impossible for there to be any difference between vials within a batch. The lab's report – on the HPLC chromatogram – advised all vials were similar and did not comment on the disparity between height of peak at 15 mins in 2 x dregs. The lab attributed the extra two major peaks in the vials to an unlisted ingredient (when questioned the manufacturer resorted to legalese, but it is unlikely there are any unlisted ingredients in the vials).
The lab considers the method it used its IP and will not disclose. However, it used a phosphate buffer. After HPLC there was no residue left to analyse in the 10 x dregs. The lab suggested it could develop a different method, suitable for LC-MS, and run a sample from the expired or current vial. It offered to provide raw data on 20 peaks but I would not know which, if any, of the 20 peaks corresponded to the two unidentified major peaks found in previous HPLC. I couldn't see the point of this exercise.
I sent all samples to another lab (at a major university). The lab advised there was no residue for analysis in the 10 x dregs. It analysed a sample from the expired vial and from a new (unopened) ampoule of Methycobal®. The previous lab would not disclose its method so this lab used the method outlined in Japanese Pharmacopoeia, although it used 361 nm rather than 266 nm. This lab could not find the additional two major peaks (using C8 reverse phase ODS column with phosphate/methanol buffer it found only MeCbl and OHCbl in both samples, which it identified using MS). In further attempt to find the additional two major peaks the lab used a C18 column with water and acetonitrile under acidic conditions but chromatograms from the two samples again looked identical (with two major peaks). The lab attempted to identify these two fractions using static nanospray MS but results were inconclusive – "It is worth noting the fractions collected did not contain the pink colour common to all cobalamins. . . . The ion counts from all the fractions were quite low which was surprising given that the fractions should have been very concentrated."
The analytical chemist later elaborated on this aspect of her report –
"I cannot say definitively that these peaks from the C18 column are not cobalamin. It is possible that only a small amount of cobalamin eluted and the majority remained on the column. However, it is also possible that it was not cobalamin but something else which did not ionise using ESI and therefore could not be identified. The evidence is not conclusive one way or the other."
The samples were returned to the first lab for repeat analysis under identical conditions (I requested this include using the same HPLC analyser and operator).
The lab was certain its previous HPLC did not find ghost peaks and was sure it would find the peaks again, so it considered my request for identical conditions unnecessary.
HPLC was run using same method but different analyser and operator. The results were more or less nonsensical. The lab advised it was the fault of the samples (it claimed the university lab had most likely mishandled the vials/ampoule). The chemist advised that he believed material in vials and ampoule had fully degraded to OHCbl prior to analysis. I thought the results indicated the samples had degraded rapidly during HPLC.
Eventually the lab agreed to run HPLC again, but again declined to use original analyser and operator.
This time it checked degradation of samples over time (and included an MECbl standard purchased from Sigma-Aldrich).
Results indicated that material in the vials and ampoule had not degraded (plenty of MeCbl was present). However, results also indicated that samples degraded rapidly (to OHCbl) when in the buffered diluent that was used in original HPLC analysis – samples completely degraded to OHCbl after 12 hours in autosampler. And yet, during the original HPLC, four of the samples sat in the autosampler for approx 20 hours before being reanalysed at 9 am the following morning, and those samples showed no sign of degradation during storage (the 2 x outlier dregs were among these four samples). When asked to explain this discrepancy the lab advised that the original autosampler was refrigerated whereas the one used for the time study was not.
The lab now offers to inject a single sample (from the expired vial) using the original analyser and the original operator. This almost meets my request to rerun the analysis under identical conditions, except for the method of injection (autosampler vs manual injection). In reading through many troubleshooting guides available online I get the impression that manual injection (if done well, i.e. completely fill the loop) is more likely to produce reliable result than injection from an autosampler. Also, will temperature of injection vary (i.e. will manual injection be at same temperature as one from refrigerated autosampler)? How important is temperature?
Is it unusual for ghost peaks to produce such orderly results?
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Hi, I also get two peaks for pure methylcobalamin standard every time I run. I am just wondering are those isomers or are those methylcobalamine and hydroxycobalamine. How do I get to know it? Thanks.
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I came across the bi-amperometric technique in analytic chemistry, but I don't understand why the analysis is possible only if the sample contains reversible redox couples. Before of that I'd like to understand when a redox reaction could be defined as reversible and when it cannot.
Thanks in advance.
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Commonly, the irreversible reaction means that the equilibrium is considerably shifted to one side and the reversed reaction is too slow. Thus, truly irreversible reactions do not exist. In electrochemistry, the electron moves between an molecule and electrode, S + e = S- . So, if you change a potential, at certain point the amplitude of current will increase until all S is converted to S- . The current returns to the initial value. If now you scan potential in opposite direction, you will observe S- . If both S and S- are stable, then on reversed potential scan the oxidation of S- results in formation of S. This is one-electron electrochemically reversible process. If S- is unstable and form product P, then on reversed scan you will not see S- . This is the electrochemically irreversible process. If you are able to convert P back to S- and remove one electron from S- , you will have chemically reversible reaction.
Thus, chemically all reactions are reversible in principal. The irreversible reaction means that the reversed reaction is too slow.
In other words, reversibility is the thermodynamic term, but the reaction kinetics may affect the rate of achieving the equilibrium.
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Is there a technological niche in pharmaceutical research that makes NQR or NMR the only measurement methods practically applicable?
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My question is related to a recently completed project: "Integrating Superregenerative Principles in a Compact, Power-Efficient NMR/NQR Spectrometer: A Novel Approach with Pulsed Excitation"
I am looking for an application to commercialize the detector idea, taking advantage of its attributes such as low power consumption and simplicity of design.
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Hello,
I actually have a salt of potassium formate, but the issue is that there are many impurities in the salt. I wanted to know which analytical technique is appropriate to quantify the composition of the salt as well as identify all the impurities present in the salt.
I am thinking of HPLC and GC-MS. Which of these is better and how to go about it? Lastly, are there any better methods than the ones I have listed? There is a lab with most of the equipment, but I just want to make sure I go with the most suitable one.
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Dear Alfred,
Thanks, I will try out different methods surely and update if I get any conclusive results.
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Short Course: Statistics, Calibration Strategies and Data Processing for Analytical Measurements
Pittcon 2024, San Diego, CA, USA (Feb 24-28, 2024)
Time: Saturday, February 24, 2024, 8:30 AM to 5:00 PM (Full day course)
Short Course: SC-2561
Presenter: Dr. Nimal De Silva, Faculty Scientist, Geochemistry Laboratories, University of Ottawa, Ontario, Canada K1N 6N5
Abstract:
Over the past few decades, instrumental analysis has come a long way in terms of sensitivity, efficiency, automation, and the use of sophisticated software for instrument control and data acquisition and processing. However, the full potential of such sophistication can only be realized with the user’s understanding of the fundamentals of method optimization, statistical concepts, calibration strategies and data processing, to tailor them to the specific analytical needs without blindly accepting what the instrument can provide. The objective of this course is to provide the necessary knowledge to strategically exploit the full potential of such capabilities and commonly available spreadsheet software. Topics to be covered include Analytical Statistics, Propagation of Errors, Signal Noise, Uncertainty and Dynamic Range, Linear and Non-linear Calibration, Weighted versus Un-Weighted Regression, Optimum Selection of Calibration Range and Standard Intervals, Gravimetric versus Volumetric Standards and their Preparation, Matrix effects, Signal Drift, Standard Addition, Internal Standards, Drift Correction, Matrix Matching, Selection from multiple responses, Use and Misuse of Dynamic Range, Evaluation and Visualization of Calibrations and Data from Large Data Sets of Multiple Analytes using EXCEL, etc. Although the demonstration data sets will be primarily selected from ICPES/MS and Chromatographic measurements, the concepts discussed will be applicable to any analytical technique, and scientific measurements in general.
Learning Objectives:
After this course, you will be familiar with:
- Statistical concepts, and errors relevant to analytical measurements and calibration.
- Pros and cons of different calibration strategies.
- Optimum selection of calibration type, standards, intervals, and accurate preparation of standards.
- Interferences, and various remedies.
- Efficient use of spreadsheets for post-processing of data, refining, evaluation, and validation.
Access to a personal laptop for the participants during the course would be helpful, although internet access during the course is not necessary. However, some sample- and work-out spreadsheets, and course material need to be distributed (emailed) to the participants day before the course.
Target Audience: Analytical Technicians, Chemists, Scientists, Laboratory Managers, Students
Register for Pittcon: https://pittcon.org/register
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Dear Thiphol:
Many thanks for your interest. Currently, I don't have a recorded video. However, I may offer this course in the future on-line in a webinar format if there is sufficient interest/inquiries.
Thanks again.
Nimal
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Is there a technological niche in pharmaceutical research that makes NQR or NMR the only measurement methods practically applicable?
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Your work is really very interesting and useful .
my sincere congratulations!!
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Analytical Chemistry
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thanks for sharing, but are we now discussing Mössbauer- or Mass-Spectroscopy (or both).
Alfred
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Dear Colleagues!
I am interested in ELSD, an HPLC detector.
Is there anyone who is currently using or has used this detector?
I would appreciate it if you could share information on the problems, concerns, and advantages of using it in real world situations.
It would also be appreciated if you could introduce, for example, review articles explaining the characteristics of quantitative measurements of analogous compounds without their standards.
I would like express my gratitude to everyone in this community.
I appreciate it.
Best regards,
Yasuhiro Nishida
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Dear friend Yasuhiro Nishida
Ah, ELSD, the Evaporative Light Scattering Detector, a gem in the world of HPLC detectors! Now, let me share some insights.
Firstly, ELSD is often a savior when dealing with compounds that lack UV absorption or those that don't have a chromophore. It detects analytes based on their ability to scatter light when eluted from the column. Now, let's delve into the real-world scenarios:
**Advantages:**
1. **Universal Detection:** One of the main advantages is its universality. It can detect virtually any compound regardless of its optical properties, making it a fantastic choice for compounds with no UV absorption.
2. **Quantification of Analogous Compounds:** ELSD is particularly useful when dealing with structurally analogous compounds that might not have distinct standards. This makes it valuable for natural product analysis or in cases where obtaining pure standards is challenging.
3. **Low Detection Limits:** ELSD often provides lower detection limits compared to other detectors, which is beneficial when dealing with trace-level analysis.
**Concerns:**
1. **Baseline Drift:** ELSD is known for baseline drift, which might complicate the quantification of compounds. Strategies like using an internal standard or appropriate calibration techniques are often employed to address this issue.
2. **Sensitivity to Mobile Phase Changes:** Variations in the mobile phase composition can affect the signal intensity. Users need to carefully optimize the mobile phase to get consistent results.
3. **Sample Dependent Sensitivity:** The sensitivity of ELSD can be sample-dependent, and it might require method adjustments for different compound classes.
**Review Articles:**
1. **"Lecoeur, M., Decaudin, B., Guillotin, Y., Sautou, V., Vaccher, C., & ARMED Study Group. (2015). Comparison of high-performance liquid chromatography and supercritical fluid chromatography using evaporative light scattering detection for the determination of plasticizers in medical devices. Journal of Chromatography A, 1417, 104-115. provides a comprehensive overview.
2. **"Megoulas, N. C., & Koupparis, M. A. (2005). Twenty years of evaporative light scattering detection. Critical reviews in analytical chemistry, 35(4), 301-316., is another valuable resource.
Remember, my eager interlocutor Yasuhiro Nishida, ELSD is a versatile tool, but like any technique, it has its nuances. The key is in understanding those nuances and wielding them to your Yasuhiro Nishida advantage in the quest for chromatographic mastery!
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For determination of water contents(moisture) spectrophotometrically.
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To remove moisture from grains, natural drying is definitely not the best method: too long times, risks of product loss and uneven drying make this process almost counterproductive. Much more advantageous is to use grain dryers – mobile or tower – which allow optimal and rapid drying. The investment required for their purchase is recovered in a short time and guarantees numerous benefits, reducing losses and increasing profits.
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Currently working on a USP assay method for HPLC that requires water-saturated butyl chloride as a mobile phase and water-saturated chloroform as a diluent.
What is the whole point of using water-saturated solutions like this?
Would there be alternative ways to substitute these solutions?
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The mechanism of any chromatography method is the selective retention of specific molecules. We use many different kinds of solid and liquid phases to effect separations different gases and liquids depending on their structure and chemical properties.
You didn’t mention what particular assay you were doing, but the use of additives to the water is to change the relative solution equilibria between the solid phase, liquid phase, and analytes. Without them you would not get the desired separation of analyte peaks for analysis.
Alternative solution blends are certainly possible. Check the literature first. Otherwise, start with the solubility characteristics of the existing solution and look for something comparable with another solvent.
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In analytical chemistry, a linear model is developed on multiple concentration levels with a goal to predict target analyte concentration in an unknown sample. Will the model prediction favorize a concentration if more calibration samples at that concentration level is used in the model development? I have not found literature article on this topic.
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This is your research question "Will the model prediction favorize a concentration if more calibration samples at that concentration level is used in the model development?" you find the answer by doing several computations
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Is sample cleanup not a part of sample preparation. Are there any examples sample cleanup that are not sample preparation in analytical chemistry?
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I would say that sample preparation is a wider term.
Sometimes you do not have to perform sample cleanup because your sample is pure enough or suitable for the instrumental analysis as it is. However, you still might need some sample preparation in terms of filtering, diluting, homogenizing and so on.
Sample cleanup usually consists of some kind of extraction (either in liquid or on a sorbent), chromatographic cleanup, precipitation or similar technique. There might even be manual mechanical/macroscopic cleanup, depending on what is your sample.
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Hello everybody. Our instrument (i.e., ion chromatography) must stop working for more than 4 months because of some maintenance. My question is, during 4 months or more, does it need anything done for preservation? However, we have already removed the columns and are storing them in the refrigerator.
Thanks a lot
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Hello!
You can read the washing method and the conditions of storage for its manual, which you can download from the homepage of the manufacturer. For columns and suppressors, the conditions vary by type. The column and the suppressor (electrolytically regenerated) must be removed and stored in the specified solvent. If you follow the instructions you should have no problem.
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Couldnt find any for a long time…
I need a scientific gaps for those topic and I am doing it in an analytical chemistry lab
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Flame photometry is a widely used analytical technique for determining the concentration of certain metal ions in a solution based on their characteristic emission spectra when introduced into a flame. Despite its popularity, there are several scientific gaps and challenges associated with flame photometry:
Limited Element Detection: Flame photometry is primarily used for alkali and alkaline earth metal ions. There is a limitation in detecting transition metals and other elements using traditional flame photometry techniques.
Interference Issues: Flame photometry can suffer from interference due to the presence of other elements or compounds in the sample. This can lead to inaccurate results and complicates the analysis, especially when dealing with complex sample matrices.
Sensitivity and Detection Limits: The sensitivity of flame photometry is relatively lower compared to other modern spectroscopic techniques, such as inductively coupled plasma-optical emission spectroscopy (ICP-OES) or inductively coupled plasma-mass spectrometry (ICP-MS). Improving sensitivity and lower detection limits is an ongoing challenge.
Sample Preparation: Sample preparation is crucial in flame photometry, and the techniques used can affect the accuracy and precision of the results. There is a need for standardized sample preparation methods to ensure consistency and reliability across different laboratories and applications.
Quantitative Analysis: Achieving accurate quantitative analysis, especially in complex samples, is challenging. Calibration methods and techniques need continuous refinement to enhance accuracy and reliability in quantitative measurements.
Instrumentation and Miniaturization: There is a need for the development of more compact and portable flame photometers for field applications. Miniaturization of the instrumentation can open up new possibilities for on-site analysis and real-time monitoring in various fields, including environmental monitoring and clinical diagnostics.
Combination with Other Techniques: Integrating flame photometry with other analytical techniques, such as chromatography or mass spectrometry, can provide complementary information about the sample composition. Research into effective combinations and methodologies is essential for comprehensive analysis.
Data Analysis and Automation: With the advancement of technology, there is a need for improved data analysis methods, including automated data processing and interpretation algorithms. Automation can reduce human error and increase the efficiency of the analysis process.
Environmental and Safety Concerns: Research into the environmental impact of flame photometry techniques, including waste disposal and energy consumption, is important. Additionally, ensuring the safety of operators working with flame photometers and associated chemicals is a continuous concern.
Addressing these scientific gaps will contribute to the advancement of flame photometry and enhance its capabilities in various fields of research and industry.
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What is the difference between Principal Component Analysis (PCA) and Partial Least Square (PLS)? In which conditions is it better to use PCA over PLS practically, let's say in environmental chemistry or analytical chemistry? Or, even can we combine both methods? Thanks for your explanations.
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Hi! This is how ChatGPT answered your question:
Principal Component Analysis (PCA) and Partial Least Squares (PLS) are both multivariate data analysis techniques used in chemometrics. While they share some similarities, they are used for different purposes and have different underlying principles.
Principle Component Analysis (PCA):
PCA is primarily used for dimensionality reduction and identifying patterns or relationships in high-dimensional data. It transforms the original variables into a new set of uncorrelated variables called principal components. These components are ordered in terms of the amount of variance they explain. PCA aims to maximize the explained variance with the fewest number of components.
Partial Least Squares (PLS):
PLS, on the other hand, is used for regression and predictive modeling. It finds linear combinations of the original variables (called latent variables) that are strongly related to a response variable. PLS maximizes the covariance between the predictors and the response and extracts components accordingly. It is particularly useful when the number of predictors is large, and collinearity between predictors is present.
In terms of practical use in environmental chemistry or analytical chemistry:
PCA is often employed when the main objective is to reduce the dimensionality of the dataset, explore patterns and relationships between variables, or visualize high-dimensional data. It helps in identifying outliers, clustering observations, and understanding the dominant factors driving the variation in the data.
PLS is useful when there is a need for prediction or modeling, especially when dealing with complex datasets, high collinearity, or multicollinearity. It handles situations where the number of predictors is significantly larger than the number of observations.
Both methods can be combined and utilized together when necessary. For instance, PCA can be used for data preprocessing and visualization, identifying outlier samples, or selecting variables to be used in subsequent PLS modeling. By reducing the dimensionality, PCA can enhance the efficiency of PLS models by reducing noise and overfitting.
In conclusion, the choice between PCA and PLS depends on the specific goals of the analysis. PCA is suitable for dimensionality reduction and exploratory data analysis, while PLS is more appropriate for predictive modeling. Both methods can be combined to leverage the strengths of each when dealing with complex data in environmental or analytical chemistry applications.
If you need more detailed explanations, try asking ChatGPT specific questions. It is best, however, to study problems in a traditional way, i.e. from academic textbooks and specialist studies in specific fields.
ZJ
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The Laboratory for Analytical Chemistry and Industrial Analysis at the Faculty of Chemistry and Chemical Engineering, University of Maribor, is seeking talented individuals to join our team. With cutting-edge research and state-of-the-art equipment, this is an opportunity to advance your career in a vibrant and innovative environment.
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  • Strong oral and written English communication skills are required.
3️⃣ Experienced Operator for ICP-MS (possibly also ETAAS):
  • Bring your expertise in operating ICP-MS to contribute to our research endeavors.
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If you are interested in any of these exciting opportunities, please send your CV, highlighting your demonstrated skills, to matjaz.finsgar@um.si.
We are looking forward to work with you and unlock new frontiers in analytical chemistry!
Note: In case you have any further questions or require additional information, please do not hesitate to reach out.
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I'm ready
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Dear researchers,
I would like to ask you whether the retention of analytes of interest on the C18 column can be slightly affected by buffer concentration.
I have analyzed a mixture containing sulpiride (weak base) and diclofenac (weak acid) at 250 ng/mL on the C18 column with mobile phase A: ammonium formate and mobile phase B: methanol.
I have observed that when the concentration level of ammonium formate increased from 2mM, 5mM, to 10mM, the retention time of sulpiride slightly decreased from 6.72 min, 6.52 min to 6.46 min respectively, whereas that of diclofenac slightly increased from 10.04 min, 10.17 min to 10.28 min respectively.
As far as I am concerned, for a basic compound such as sulpiride, an increase in buffer concentration (ammonium formate) can result in a decrease in silanol activity so a positively charged compound such as sulpiride can have a slight loss of retention due to the ion exchange interaction between the compound and silanol group during a loading step. Consequently, the retention time of sulpiride was slightly decreased with an increase in buffer concentration.
However, for an acidic compound such as diclofenac, it is quite difficult to explain this phenomenon. In my opinion, it seems that when the concentration level of ammonium formate increases, the pH of the mobile phase slightly increases so the charged state degree of diclofenac slightly increases either. As a result, the energy configuration of diclofenac diffusing inside the pore of the C18 column is lower at a higher concentration level of ammonium formate (10mM) so it will have more interaction surface area with the C18 column, leading to more retention. However, this explanation seems not to be convincible because the higher charged state degree of diclofenac is, the more soluble is and the less retention is.
However, for the retention behavior of sulpiride and diclofenac, the above explanations are just my own opinion. Of course, I am not sure whether they are right or wrong.
If someone here can help me clear the retention behavior of sulpiride and diclofenac, I am really happy to listen to your valuable suggestions.
Thank you so much in advance,
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Back to your original question (and I am done with this thread)... You observed a small (tiny) difference in Rt from small changes you made to the mobile phase composition. No worries, this is normal because no two columns are the same and each may interact to a different degree (or none at all) when you make small changes to the mobile phase composition. Try 20 different C18 columns and you may find some show no change at all, some do. Pick and choose the one that you want for the application (this is what we do in analytical laboratories). The reason for the observed change (change, not "drift") is due to multiple interactions of the solute on the surface of the support. Hard to say if it is electronic or ionization in nature, but it is so small, practically, it does not matter. All chromatographers are familiar with this (no need to 'explain it'). Run enough samples and you will see it. In fact, the one thing that they might question is why you would use a mobile phase of just ammonium formate without an acid (e.g.formic). Why not use a buffer? For LC-MS applications, most would benefit from such a solution to promote ionization and maybe change the separation factor too (depends on samples).
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Hello,
When working with methanol, I noticed that I could never take the exact volume of methanol with micropipette.
Is there any other tool or method that could solve this problem?
Many thanks for your concern,
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  • Michal, I am pleased that the eVOL works so well for you. It is a device I developed with my team at SGE. It is disappointing that it has apparently been discontinued but the same team that developed the eVOL have since developed at ePrep a far more capable automatic syringe which I mentioned above. https://www.digivol.com.au
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application
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Oxidative coupling reactions in analytical chemistry play a significant role in various applications, particularly in the field of spectrophotometry. These reactions involve the coupling of certain chemical species through an oxidative process, resulting in the formation of colored or fluorescent compounds. The composition of colored or fluorescent products can be measured and quantified using spectrophotometric techniques, enabling the determination of specific analytes in a sample.
Here are some specific applications of oxidative coupling reactions in analytical chemistry:
1- Determination of Phenolic Compounds: Oxidative coupling reactions are commonly used to determine phenolic compounds in various samples, such as environmental samples, food, and beverages. These compounds react with specific reagents to produce colored products, and the intensity of the color formed is proportional to the concentration of the phenolic compound present in the sample. This method allows for sensitive and selective analysis of phenolic compounds.
2- Measurement of Aromatic Amines: Aromatic amines can be determined using oxidative coupling reactions with suitable reagents. The resulting colored products can be quantified using spectrophotometric techniques, providing a means for analyzing these compounds in different samples.
3- Analysis of Polyphenols: Polyphenols, which are abundant in various plant-derived products such as fruits, vegetables, and beverages, can be quantified using oxidative coupling reactions. These reactions often involve specific metal catalysts to form colored complexes with the polyphenols, allowing for their sensitive detection and measurement.
4- Detection of Nitrogen Species: Oxidative coupling reactions have been employed for the detection and measurement of nitrogen-containing species, such as nitrites and nitrates. These reactions can lead to the formation of colored products that can be easily detected and quantified.
5- Environmental Monitoring: Oxidative coupling reactions find applications in environmental monitoring to analyze pollutants and contaminants in water and soil samples. By using suitable reagents, certain pollutants can undergo oxidative coupling to produce colored products, facilitating their identification and quantification.
6- Clinical Analysis: In clinical chemistry, oxidative coupling reactions can be used for the determination of specific analytes in biological samples, such as blood and urine. These reactions can offer a sensitive and specific means of measuring certain compounds of interest in various disease diagnoses and monitoring applications.
Overall, oxidative coupling reactions in analytical chemistry provide valuable tools for the selective and sensitive detection and quantification of various compounds of interest, making them essential in many research, environmental, and industrial applications.
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Many methods call for reconstituting experimental samples in methanol/ water, but diluting the standards with some sort of plasma (typically blank bovine plasma). Why not dilute the standards in methanol/ water to match the experimental samples?
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The choice of diluent for preparing standards and experimental samples in analytical methods can depend on several factors, including the solubility of the analyte, compatibility with the analysis technique, and the desired matrix for calibration.
Here are some reasons why diluting standards with plasma or other biological matrices may be preferred over diluting them with methanol/water to match the experimental samples:
  1. Matrix Effects: Matrix effects refer to the influence of the sample matrix on the analyte's measurement or detection. Biological matrices, such as plasma, contain various endogenous components (proteins, lipids, metabolites) that can interact with the analyte and affect its detection or measurement. By diluting the standards in a similar matrix as the samples (plasma), it helps account for these matrix effects and improves the accuracy and precision of the calibration.
  2. Similarity to Sample Composition: Diluting the standards in a matrix like plasma makes them more representative of the actual samples being analyzed. This can help account for any potential differences in analyte recovery or behavior between the standard solution and the actual sample matrix, leading to more accurate and reliable results.
  3. Mimicking Sample Extraction Procedures: In some cases, the plasma matrix used for dilution may mimic the extraction or sample preparation procedures applied to the experimental samples. By using the same matrix for standards and samples, any extraction or matrix effects introduced during sample preparation can be more accurately accounted for, improving the overall validity of the results.
  4. Method Validation and Comparison: Using plasma as the diluent for standards allows for direct comparison of the calibration curve and sample results. It facilitates method validation by ensuring that the standard curve represents the analyte's behavior in the same matrix as the samples, providing more meaningful and applicable results.
It's important to note that the choice of diluent depends on the specific analytical method, the analyte being measured, and the overall objective of the analysis. Methanol/water dilution may still be appropriate for some cases where the analyte is stable and soluble in that solvent mixture and if matrix effects are not a significant concern.
Ultimately, the decision on the diluent should be made based on method requirements, validation considerations, and the desired accuracy and reliability of the results. It is recommended to consult the specific method or assay protocol, as well as relevant literature or guidelines, for guidance on appropriate dilution procedures for your specific analysis.
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My peptide is Cholecystokinin (CCK8), MW=1142.35 (COOH-D-Y-M-G-W-M-D-F-NH2).
Stock solution in NH4OH 0.05M and working solution in acetonitrile.
I do MS infusion at conc. 500 ng/ml in acetonitrile.
I use two LC/MS machines: Micromass - Quattro Premier XE of Waters (Tamdem Quadrupole) and Applied Biosystems - API 3200 LC/MS/MS (triple quadrupole)
I run ES + but I can not see the peak at 1+, 2+, 3+,4+,...for [M+H], [M+Na], [M+K]
I wonder whether I have missed some other adduct ions that could be created during the ionization?
Or maybe my peptide is being degraded during preparing the sample?
Please give me some advice! Thank you!
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Here are the other points, you may lean on;
If the purpose is quantification or purity check, LC-UV would be nice to use since the octapeptide you have several aromatic rings and would be highly responsive,
secondly, 500 ppb may be a low conc. to conduct a full scan..especially when the ionization efficiency is low.
Third, I would prefer combined flow scanning in place of infusion...In this mode, you are not taking benefits of the mobile phases which present donors to improve ionization...You should combine the lc flow and infusion (acid and/or DMSO additives in phases for pos ESI in this case) and retest the response...
By solving the peptide in an alkaline condition you are directing the peptide to deprotonation and this makes the peptide more amenable to neg ESI...If it is soluble in ACN directly..prepare your stock in ACN and dilute it with the same solvent, I prefer not to use aggressive pH which is not convenient for most of the peptides to the unintended H exchanges...
Last but not least, If the peptide is hydrophobic and dissolves only in organic solvents this is susceptible to be efficiently ionized in APCI, APPI rather than ESI...You may look for these alternative ionization techniques if MS analysis is the bottleneck and the abovementioned suggestions are useless...
Good Luck...
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Does someone have any practical experience with those columns?
The producer suggest ODS-B are more suitable for hydrophilic analytes, but without any concrete information.
Can they be used interchangeably with ODS-A columns? Are there expected changes in retention times of non-polar analytes? Are there differences in their pH tolerance?
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Sir,
How can we remove blockage of Waters Spherisorb ODS2 column? Any solution you have?
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Green analytical procedure index (GAPI) and National environmental methods index (NEMI) are assessment tools used for evaluating the greenness of an analytical method. Is there is any software through which GAPI and NEMI pictograms are constructed?
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I am working on a project that requires the measurement of neuromelanin purity, and I have found papers that say that they have measured the purity, but they do not say how ( ).
Neuromelanin does not have a commercially available 100% standard, so I cannot do typical comparisons. Does anyone know where to begin or how to do the purity measurements?
Any help would be appreciated.
Thank you!
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There are several methods for measuring the purity of neuromelanin, including:
Spectrophotometry: This technique can be used to measure the light absorption of neuromelanin at different wavelengths. The purity of neuromelanin can be determined by comparing the resulting spectra with reference spectra.
Chromatography: This technique allows the separation of different components of a brain tissue sample using appropriate solvents. The purity of neuromelanin can be determined by analyzing the chromatographic peaks corresponding to neuromelanin and comparing their intensity with other components.
Electron microscopy: With this technique it is possible to observe the structure of neuromelanin at a microscopic level. The purity of neuromelanin can be determined by analyzing the morphology and size of neuromelanin granules.
It should be noted that measuring the purity of neuromelanin can be difficult because there are other similar pigments in the brain, such as melanin and lipofuscin. Therefore, it is important to validate the obtained results using different methods and compare the results with known reference samples.
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I'm a Chemistry student currently working on a thesis that involves phytoremediation of Lead in aqueous solution using a specific plant.
The FTIR results for both the stems and leaves of the plant after phytoremediation are almost identical, having the presence of O-H stretch and C-H stretch on both IR spectrum.
The FTIR result for the roots after phytoremediation, however, showed a possible trace amount of H2O at 3457.1 cm-1 (it was a tiny peak, therefore it cannot be called an O-H stretch), along with the presence of a C-H stretch and C=O stretch.
I need help in understanding what caused this deviation from the two other samples (stems and leaves). Could it be the presence of the metal in the root sample or are there any factors that I need to consider?
Thank you to anyone who'd be willing to give their insight/s on this, it would really help me a lot.
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Princess Olivar Tuquero , as you noted previous researchers identified the IF band shift when affected by metals. Assuming that is correct, then the only thing necessary to correlate your FTIR results with the metal content is a graph of the amount of observed band shift to the amount of lead found.
Secondary correlations are not generally preferred analytically, but are sometimes necessary. If you are trying to identify the particular chemical/structure actually doing the adsorption of the lead I can see how combining both might seem simpler. However, as long as you have an AAS it would be better to use it for the metal analysis instead of trying to infer it from the IR. If that is just to explain why your IR peaks are shifted a bit, the metal content would explain that via reference to the paper you mentioned.
As normal growth in plants transports nutrients from the roots ultimately to the leaves it is not surprising to find the highest concentrations of any other compound taken up there as well. I would not expect to find them in the same concentrations evenly throughout the plant structure.
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Hello
Laboratory techniques of biological and analytical chemistry to investigate the anticancer properties of plant samples.
thanks
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Olá, ensaios com culturas celulares.
Antes de testar em células, sugiro fazer uma ampla caracterização de sua amostra (planta), tanto com HPLC, como testes básicos de atividade antioxidante (colorimétrico) entre outros. De acordo com a caracterização você consegue direcionar para algumas linhagens celulares.
Dependendo da estrutura da sua Universidade e verba você consegue fazer muitos testes.
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Dear to whom it may concern,
I would like to kindly ask you about the ionization of acidic and salty forms of a given compound in electrospray ionization.
To be more specific, when I successively infused the reference standard solutions of atorvastatin in both its acidic (atorvastatin with an exact mass of 558.25) and salty (atorvastatin calcium with an exact mass of 1154.45) forms into the ionization source (electrospray ionization known as ESI) of the mass spectrometer, I always obtained the same precursor ion (m/z 559.5 in positive mode) of its forms.
I do not understand the reason why the atorvastatin calcium could show the same precursor ion as that of the acidic form of atorvastatin.
May you please give me an explanation of how the salty form of atorvastatin is ionized in ESI, resulting in the same precursor ion as that of the acidic form of atorvastatin?
Thank you so much.
Best regards,
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To my understanding, acetonitrile, methanol, isopropoanol etc. act as electron donors in ESI conditions, enhancing ionization in ESI+. This is one of the reason why ionization in ESI+ is enhanced by solvents (the other is their faster vaporization than water in ESI conditions).
some solvents are better electron donors than others, and you may notice signal enhancement switching from one to another...
hope this helps...
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I want to quantify the chromium in solution. I want to know whether atomic adsorption spectroscopy is better or UV vis spectrophotometer.
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Noor Ul Ain , Generally atomic adsorption spectroscopy will be better. You have better selectivity and lower quantification limit.
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According to the pourbaix diagram of Fe(2+), it should be dissolve in pH<6, but it is solid even in pH=1. I realy dont know what is the reason.
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The ferrous chloride salt (possibly hydrated) can be generally expected to be partially oxidized, at least to trace level. When (freshly) dissolved in aq. dil. HCl, you may consider to reduce contaminant ferric ions to the ferrous state by adding electrolytic iron powder (a few wt% of the weighted salt). Then the sol. should be heated (not boiled) to facilitate ferric to ferrous reduction and the dissolution of any possibly excess of ferrous chloride; cooled to room temperature; being then either vacuum filtered while using nitrogen as blanketing gas, or pressure filtered by using nitrogen as pressurizing gas. Hydrogen can possibly be released during the purification process, owing to the concomitant reaction of metallic iron with HCl: Fe + 2HCl → FeCl2 + H2. Water should be either distilled or both deionized and N2-purged or boiled. The purified ferrous chloride / HCl aq. solution may then be redox-titrated, if required.
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I am looking for a method to completely remove proteins from plasma without using heat or adding salt ions. I have considered using activated carbon, but I am unsure if this is feasible. Are there any other effective methods for achieving this goal?
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Dear Sir you may try the protein separation with foam fractionation coloumn. it would suppose to help you
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Chemical Informations
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Greetings Ali Safaa
To solve for molarity (M) in the equation:
ppm = M x m.wt x 1000
We can rearrange the equation as follows:
M = ppm / (m.wt x 1000)
So if you have a solution with a concentration of 50 ug/ml and you want to know the molarity, you would first need to know the molecular weight of the solute. Let's say the molecular weight is 100 g/mol.
  1. Convert ug/ml to ppm by multiplying by 1000:
50 ug/ml x 1000 = 50,000 ppm
  1. Plug in the values into the equation:
M = 50,000 ppm / (100 g/mol x 1000)
M = 0.5 M
Therefore, the molarity of the solution is 0.5 M.
It is important to note that ug/ml and ppm are not equivalent units of measurement. Ug/ml is a unit of concentration based on mass per volume, while ppm is a unit of concentration based on the number of parts per million. To convert from ug/ml to ppm, you would need to know the density of the solution and the molecular weight of the solute.
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In the Column treatment of aqueous solution of Chromium Removal by Adsorption
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Treating bark with acid (HCl) first and then with base (NaOH) second is a common method for isolating plant compounds for analysis or extraction, such as tannins, lignin, and cellulose. This method is known as acid-base treatment or A/B extraction.
The reason for this order of treatment is that acid treatment hydrolyzes and breaks down the plant cell walls, making the cell contents more accessible for extraction. Acid treatment can also help to remove impurities, such as pigments and waxes, from the sample.
After acid treatment, the sample is then neutralized with a base, typically sodium hydroxide (NaOH), to restore the pH to a neutral or slightly alkaline state. The neutralization step is important to prevent the acid from interfering with subsequent analytical techniques or reactions.
The use of acid and base treatments in this order allows for selective extraction of different plant compounds based on their solubility and chemical properties. For example, tannins are more soluble in acidic solutions, while lignin and cellulose are more soluble in basic solutions.
Treating the bark with base first would result in a saponification reaction, where the ester linkages in the plant compounds would be hydrolyzed by the base, resulting in a loss of their original structure and properties. Therefore, treating the bark with acid first and then with base is the preferred order for A/B extraction of plant compounds from bark.
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Hello, I am a student in analytical chemistry, I am supposed to prepare samples, quality control, and calibration serial dilution for a forensic project which is working on larvae and flies (for quantification of benzodiazpines).
would you please correct what I wrote here even in terms of the specific volume and concentration?
Sample prep:
Collected sample with matrix is spiked with target analytes and RS (recovery standard)
Sample is extracted (prepared for analysis)
IS (internal standard is spiked before the analysis
Cal prep:
Calibration standards (mixture of target analytes and RS) are prepared with serial dilution
IS is added before the analysis
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I appreciate your response,
you wrote " Prepare a series of quality control samples by spiking known amounts of the target analytes and RS into a matrix. Extract the QC samples to prepare them for analysis"
I have some questions:
1) It seems the QC sample preparation is the same with the sample preparation, what is the difference exactly?
2) what do you mean by "series of QC samples" ?
my advisor told me the feature of QC samples is the fact that we can consider their recovery as 100%,, I thought it means we have to do the same process like the sample preparation BUT add the RS after the extraction process (because in this way we know that the QC recovery is 100%)
I dont know, maybe I am wrong. I am working with HPLC-ESI-mass
another question, you wrote I need to spike the RS into the calibration serial dilution too, is there any extraction process for calibration serial dilution?
waiting for your response, Zeinab.
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I have powdered diphenylcarbazide and I want to make 0.5% w/v solution of diphenyl carbazide. Since it is dissolved in acetone.
Does it mean 0.5 g in 100 mL acetone? Is there any need to add distilled water?
In literature it is prepared by dissolving in acetone and then 200 mL distilled water was added.
Thanks for your guidance
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It is likely the presence of water will help to stabilise the metal ions. In the presence of pure acetone the inorganic metal may be insoluble and unavailable to react?
As per above, taking the 0,5 gram and dissolving in pure acetone, then making this up to 100ml, maybe using 50mL acetone, and then using distilled water to complete the volume requirement?
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I want to deacetylate the chitosan in sodium hydroxide (50 % w/w) solution. Does that mean 50 g NaOH in 50 mL of distilled water? What should be the appropriate time and temperature for the complete process? There are different temperatures and times are reported in literature.
Thank you for your help!
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The reaction time and the temprature depends on the level of deacetylation that you would like to achieve. If you let your mixture react longer then the level of deacetylation will be higher.
You might need to experiment a bit till you get a product that has the desired characteristics. Or if you have a procedure for a product with the desired characteristics in the literature then you can simply follow that and get some good results.
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I made several reactions with 3,5-Dinitrobenzoyl chloride. When I looked at similar reactions for this substance, no heat was ever given in the reaction (even though heat increases the yield).
The interesting thing is that this substance turns black as soon as the heat is given to the reaction environment. Due to the fact that, theoretically, the polymerization of this material is impossible. Do you know the reason why they do not give heat to this material?
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Hello everyone,
I want to calculate a ratio, but for some measurements, I have <LOD in the denominator
There is actually a range of possible numbers <LOD
One solution could be to consider: =LOD, or LOD/2, etc. ?
Are there methodological references which I can confront?
Thank you in advance
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There are some good recommendations here. However, my caveat is that it exemplifies the danger of trusting (or using) statistics as a substitute for valid science. If you can't OBSERVE it in some way (<LOD) you really cannot make valid assumptions or conclusions about it. Wether you need more accurate assay methods or more experiments for more data, you really cannot legitimately just ignore that weakness and obscure it with mathematical manipulations of other data.
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Hello everyone,
I want to calculate a ratio, but for some measurements, I have <LOD in the denominator
There is actually a range of possible numbers <LOD
One solution could be to consider: =LOD, or LOD/2, etc. ?
Are there methodological references which I can confront?
Thank you in advance
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When calculating ratios with a Limit of Detection (LOD) in the denominator, there are a few different approaches that can be used, depending on the specific context and the desired level of accuracy. Here are a few examples:
  1. Substitute a value below the LOD: One option is to substitute a value below the LOD, such as half the LOD, in the denominator. This will give a conservative estimate of the ratio, but it may not be very accurate.
  2. Substitute a value above the LOD: Another option is to substitute a value above the LOD, such as the LOD +1, in the denominator. This will give a less conservative estimate of the ratio, but it may not be very accurate.
  3. Use a statistical method: A more accurate approach is to use a statistical method to estimate the true value of the ratio. For example, the method of imputed ratios or the method of adjusted ratios can be used.
  4. Report the ratio as <LOD: Another option is to report the ratio as <LOD, this means that the value is less than the limit of detection.
It is important to note that the best approach will depend on the specific context of the measurement, the desired level of accuracy, and the intended use of the ratio. It's always advisable to consult with an expert or statistician to determine the most appropriate approach.
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Hello
I have received the FTIR graph after the analysis of the sample but the graph isn't aligned to the baseline. I am attaching the file. Kindly guide me is it the sample or machine error?
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  • Run a standard material
  • Contact the manufacturer or distributor/agent with the above
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How many grams of K2Cr2O7 to dissolve it in 1 liter Distilled water to obtain 50 ppm of Chromium? to become aqueous solution, Is there a specific equation to apply? Thanks
Ali
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Ali Safaa I think that depends on what purpose you need that solution for. For example, if you needed to make a solution with a concentration of just the chromium(IV) ion in an analytical study, you would need half of that mass you calculated above because for every mole of potassium dichromate, there are two moles of chromium(IV). Here I post the stoichiometric relationship that I made to calculate that concentration and I hope it makes sense.
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We are looking for a way to identify the composition of a polymer blend that we do not know the composition. The composition is based on a polyurethan polymer, silicone elastomer, polyester-based polymer, and enzyme (that we know).
We have done some research and it seems that FTIR combined with TGA (Thermogravimetric analysis) can possibly be helpful for polymer blend identification.
We hope that our colleagues can share their point of views on how to approach the situation and suggest any helpful tools that can help us.
Thank you in advance.
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That is depends upon the which based polyurethan water based or solvent based , chromatography technique also useful
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Is it necessary to carry out validation tests on model mixtures prepared using both substances, or is it enough to use one substance for testing?
What validation tests should be carried out for an "alternative" substance only? If there is a quantitative method: what validation tests should be checked, for example?
Is it necessary to use a risk-based approach to determine validation tests when registering a new alternative substance during revalidation?
I'm really looking forward to your response, thank You for your attention!
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Of course you will have to perform a QA audit of the new manufacturer's facility, but you could have a limited method validation (which should include specificity, linearity (which you could derive the LOD and LOQ), repeatability... Don't be surprised if the impurity profile is different since it is dependent on the manufacturing process. You should also put the finished drug product that is using the new manufacturer's API, on stability.
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Hi All,
We are trying to add Magnesium & Strontium dopants to our Beta Tricalcium Phosphate (b-TCP) powder. Recently, we obtained EDS data on the undoped b-TCP and doped b-TCP to see if the investigate if the doping was successful. However, we are observing higher weight percentages of the Magnesium dopant in the undoped b-TCP and we can't figure out why we are observing this trend. After we first observed this, we have used EDS to look at multiple different samples but they are all showing similar results. We have contacted the manufacturer of the pure, undoped, b-TCP powder and they agree that we should not be seeing this. We are pretty confident that we don't have contaminated, undoped, pure b-TCP powder. But we still aren't sure what might be causing these results. The attached Mg Map Data is from the undoped b-TCP only but the spreadsheet shows some examples of the weight% values we are observing.
Does anyone have any ideas that might explain the results? Are there any recommendations for how we can discriminate between potentially overlapping signals that might be giving false Mg signals?
Thanks!
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please forget about those ugly very low numbers of % and even the variation of these numbers in your maps.
To my opinion you only 'see' the noise in the background of your EDS spectra around the energy position the Mg K-alphas ( ~1,25keV) and the Sr L-alphas (~1,8keV).
You may share some typical measured spectra; so we will have an impression on the quality of the statistical noise or even of peak overlapings in these regions.
Many thanks in advance
and best regards
G.M.
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LOD and LOC can be calculated from the calibration plot. One of the ways to do it is:
LOD = 3 SD(intercept)/S
LOC = 10 SD(intercept)/S
Where SD is the standard deviation of the intercept and S is the slope.
However, I have seen that standard error (SE) is often used instead of SD. But, SE is not the same that SD:
SD = SE*(N)^1/2
Thus, LOD and LOC from SE should be less than LOD and LOC from SD. However, I used SE for my work because I noticed that when I used SD, LOD and LOC were very high.
What do you think about using SE and SD for LOD and LOC estimation?
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SD estimates the variability of the measurement (mean) for a single sample/population.
SE estimates the variability of the measurement (mean) when repeating different samples within the same total population.
As such, and I'm using the exact same LOD/LOQ methodology as you are, my philosophy so far is to use :
  • SD when I have run only one "sample" (min five calibration curves, generally) when developing the analytical method : I do my calibrations only when developing.
  • SE when I have developed the method and used it for some time : compute SDs for all cumulated calibration intercepts up to now and divide by fixed N (number of accumulated calibrations you chose when developing, e.g. 5 or 10).
Thus, SD provides a very conservative estimation for LOD/LOQ at the start of the project and SE will provide a better estimation when the method has become routiine.
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Hello, I am a student investigating acetate ions in wood.
My current mobile phase is 1000:0.5 (H2O;H2SO4) and I do not have the most resolute peak for acetate. The column is a H+ Column packed with sulfonated styrene /divinylbenzene copolymer backbone. What is a mobile phase worth trying?
pH mobile phase currently is ~2.0
pKA acetic acid is 4.76.
Analyt is acetate in NaOH with a basic pH.
Also is a buffer useful, if so which buffer is needed for acetate ions?
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I trying to analyze EPDM using pyrolysis gcms.
Does anyone know where I can get the standard reference materials?
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EPDM can be found in parts such as water system O-rings, hoses, and gaskets, as well as in electrical insulators and connectors for wires and cables. It is also used in accumulator bladders, diaphragms, grommets, and belts.
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Hello,
In the chromatogram you can see that the second peak (retention at 4 min), which is an acetate peak, has huge tailing which is known for the sample that is measured but I need to know how I can separate the component that causes the tailing.
My mobile phase is MilliQ/H2SO4 (1000;0.5) using an H+ Ion exchange column with UV detection. Method uses a flow rate of 0.8 ml/min with a column temperature of 40 degrees for the first 8 minutes.
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Typically, tailing is an indication that the API is not 'happy' with the mobile phase system and the retention (separation) it provides. It can be resolved by using a stronger solvent (IPA instead of Methanol) or a higher percentage of organic (60% instead of 50% Methanol) in order to 'boot' the molecule off the column. This will lower you retention time and sharpen the peak.
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thanks in advance on sharing the method
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Please find the attached article - Determination of Chloride Content in Cementitious Materials. (It may be helpful)
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We are trying to determine the UV-visible spectrum for some hydroethanolic herbal extracts but we keep getting negative reading, we tried dissolving the samples in different solvents, distilled water, 5% propylene glycol and 10% propylene glycol, but the results are always negative, what could be the reason? and is there a solution for this problem?
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Hope u have this at back of ur mind: "Chromophore"
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Tannic Acid Modification.
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Dear Harsh,
Maybe i will not properly answer your question, but in my understanding tannic acid has a lot phenolic groups which are already very reactive to hydroxyl radical.
Have you ever tried to performe irradiation of tannic acid aqueous solution with ionizing radiations (i.e. electorn beam or gamma-rays ?). You will produced a lot of hydroxyl radical throught water radiolysis which should react with tannic acid.
All the best,
Nicolas
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I am searching for journals that publish reviews of books on spectroscopy, including analytical chemistry, computers in spectroscopy, and signal processing in spectroscopy.
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Though it may be a bit outdated it is one of the rare publications that studied exactly what you are looking for: Hubbard, D.E. (2011), "Chemistry book reviews: their value, sources, and number", Collection Building, Vol. 30 No. 4, pp. 172-178. https://doi.org/10.1108/01604951111181146 In Table II (see enclosed file) you see excellent titles like Journal of the American Chemical Society and Angewandte Chemie International Edition. Obviously not sure how, more than 10 years later, the ‘landscape’ of journals is, but I found a nice example in Frontiers of Chemistry (https://www.frontiersin.org/articles/10.3389/fchem.2017.00065/full ). See for more info regarding book reviews (and especially the reply by Wolfgang R. Dick ) the following question here on RG https://www.researchgate.net/post/Is_a_book_review_considered_a_publication
Best regards.
PS. Be careful with the suggestions like JETIR and IOSR. There are predatory journals out there nowadays. See for example:
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I want to estimate freezing point of a mixture made from Ehhanol (H₃CCH₂OH, MW: 46.07 g/mol) , mono propylene glycol (CH₃CH(OH)CH₂OH, MW: 76.1 g/mol) and water. And the ratio of the mixure will vary for example I can start with 1:1:1 and so on. I spent couple of week to google it but not able to figure out how to do that. If someone here have some experience with it or have some suggestion / literature then please help to solve for this problem.
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Dear Dol Lamsal,
The best and simplest choice for the phase-equilibrium calculations and studying such systems (Including Water+Alcohols+Hydrocarbons) is the CPA (Cubic Plus Association) equation of state. I suggest you verify the following references:
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I have prepared quaternized PVA. I want to measure the degree of substitution of quaternized polymer by titration. In literature, potassium chromate is mentioned as an indicator but I have potassium dichromate in my lab. Can I use this salt instead potassium chromate? AgNO3 solution is used for the titration.
Thanks for your help.
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Yes but also FTIR (point 2.4), elemental analysis via chemical or spectroscopic techniques is another way. If you are close to a biology institute, you may find Kjeldahl analyzer. My Regards
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Let's start a discussion: What do you consider are the key factors or conditions to develop voltammetric and amperometric sensors with a good analytical performance.
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For Developing the good Electrochemical sensor choosing the suitable nanomaterials related to the your project like Carbon nanotubes (CNTs) and gold nanoparticles (AuNPs) is the first condition.
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Dear All,
I'm looking for a suitable and a simple software of Chemometrics technical,
as effective tools for application in exploring chemical data in analytical chemistry, what do you recommend for beginners?
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I suggest that the easiest and the cheapest way is using web-version of MetaboAnalyst (https://www.metaboanalyst.ca/MetaboAnalyst/ModuleView.xhtml).
Best regards,
Ivan
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Dear Researchers :
I have this question and I have an hypothesis:
Why Natural HDPE, when extruded at temperatures about 100 °C (around) it has a white (but pale white), and then when the polymer cools down it color turns between white an yellow.
I understand that this phenomenon it is a general case of all LLDPE, LDPE and HDPE , and in all fabrication processes : Extrusion, injection, molding, pressing, etc.
So this is fundamentally, a chemical characteristic of the material ...
It has to do with a change in the Oxygen concentration in the material ?
Thank you all in advance,
Best Regards !
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Dear Franklin Uriel Parás Hernández, both degradation and crystallization are behind the change in color aspect. My Regards
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For chemical characterisation of my biochar samples & in order to understand it’s chemical composition better I need pyrolytic-GC/MS data of my samples, from which institute i can get this facility also i would appreciate it if anyone can share me the link.
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Hii Dr. Harsh
You may visit NIPER ,MOHALI, PUNJAB for the same.
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After ultrasonic extraction of non-freeze dried sediment samples with n-hexane, can it be directly purified by c18 solid-phase extraction? Why?
Can it be purified directly with a silica gel column? why?
Any known about these two question
Analytical Chemistry
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Thank you sir
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I need to prepare SRM from the benzoate solution to be used for calibration.
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Sodium benzoate is a salt derived from a weak acid and a strong base, so its aqueous solution is alkaline. Therefore, solutions containing sodium benzoate are assayed using a standard N/2 hydrochloric acid solution in an acid- base titration.
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I need to know the best type of bi-potentiostat instrument?
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A potentiostat is the electronic hardware required to control a three electrode cell and run most electroanalytical experiments. A Bipotentiostat and polypotentiostat are potentiostats capable of controlling two working electrodes and more than two working electrodes, respectively. In order to measure the I-V of the electrode one drives a constant current in it till the required potential between the electrode and the reference electrode is reached this is accomplished by the potentiostat. Since the reference electrode does no conduct any current and its function is to sense the potential of the electrolyte only, the current in the working electrode must continue flowing in the counter electrode.
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Do you think it is appropriate to use a photoelectrocatalytic amperometric sensor also as a voltammetric sensor?
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Photoelectrocatalysis takes advantage of the heterogeneous photocatalytic process by applying a biased potential on a photoelectrode in which the catalyst is supported. This configuration allows more effectiveness of the separation of photogenerated charges due to light irradiation with energy being higher compared to that of the band gap energy of the semiconductor, which thereby leads to an increase in the lifetime of the electron-hole pairs. Due to their unique properties, TiO2NTs have been used in many applications such as in photo(electro)catalysis , sensors , biosensors, dye-sensitized solar cells , hydrogen generation by water photoelectrolysis , photocatalytic reduction of CO2 , and biomedical-related applications .
You are right, but slightly difference, In voltammetric sensors, the current response is measured as a function of applied potential. The potential is varied either step by step or continuously in order to determine the current as a function of the cells potential. A voltammetric sensor is usually composed of three electrodes, that is, working, auxiliary, and reference.
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Hi everyone, I have a question regarding the determination of dissolved aluminium by colorimetric method using pyrocatechol violet according to ISO 10566:1994. In the preparation of 'mixed reagent', we have to add 5 mL of the aluminum standard solution (10 mg/L) into 100 mL of this mixed reagent (total volume).
My question is:
- What is the role and function of the addition of standard solution for this method? In this standard it only says "accurate addition of the aluminum standard solution is essential in order to allow a linear calibration at low concentrations".
Note: if we calculate the concentration of this aluminium standard solution in the sample is about 15 µg/L.
Thank you for your answers.
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This is a typical calibration procedure. You will need multiple concentrations to develop a quantitative response relation that you will use to estimate concentrations in your samples
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The fate of nanodrugs / nanoparticles in vivo draws a lot of attention, and many studies label fluorescent of nanodrugs / nanoparticles in order to disclose their distribution in vivo.
- What are its advantages and disadvantages ?
- Is it a reliable tool ?
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The study of the interaction of nanoparticles (NPs) with proteins is of great importance due to its relevance in several fields including nano-biosafety, nano-bioscience, nano-biomedicine, and nano-biotechnology. an introduction and a discussion of merits of fluorescent NPs compared to molecular fluorophores, labels and probes, the article assesses the kinds and specific features of nanomaterials often used in bioimaging. These include fluorescently doped silicas and sol–gels, hydrophilic polymers (hydrogels), hydrophobic organic polymers, semiconducting polymer dots, quantum dots, carbon dots, other carbonaceous nanomaterials, upconversion NPs, noble metal NPs (mainly gold and silver), various other nanomaterials, and dendrimers. Another section covers coatings and methods for surface modification of NPs..
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#Analytical Chemistry #Veterinary Drugs #Residue Analysis of Pesticides #LCMSMS
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it's quite easy:
analyte from the tissue sample (5 g) is contained in 25 ml (volume of pooled and diluted supernatants A and B). Defatting is performed by extraction with hexane which shouldn't change the analyte concentration in the aqueous (lower) layer. In order to calculate tissue concentration in ppm (or mg/kg) you should multiply concentration measured by MS (in mg/ml) with 5000. It is (1000 g/sample mass (5 g) ) x extract volume (25 ml). 1000x25/5=5000.
Best,
Dražen
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I find there are various kinds of diffusion coefficient equations, and there always exists the deviation, so can anyone introduce me some good methods for calculating the diffusion coeffients for gasphase species  with higher precision. Thanks again.
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Hi Zhepeng Tang , Did you compare the molecular diffusivity values obtained from the Fuller-Giddings and Chapman-Enskog methods? What I meant that is the Fueller-Giddings correlation is accurate too, as most of the literature suggests Chapman-Enskog method?