Analytical Chemistry - Science method

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?

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.

This position is no longer available. Thank you for your interest.

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!

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

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?

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).

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.

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

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.

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

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!!!

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:

I would greatly appreciate any advice, recommended tools, or literature that could guide me in this process.

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%.

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

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.

I received my PhD in Analytical Chemistry, am I eligible for this position?

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

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?

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.

Dear Experts,

kindly suggest me a best method to estimate the percentage of potassium sulphate in the organic fertilizers.

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 ?

What is the general mechanism of Schiff bases reaction for determination of drug in analytical chemistry ?

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?

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.

Date: 19-09-2024

Location: Online

Submission Deadline: 15-07-2024**** Extended to 1-8-2024

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What is the difference between absorption and adsorption?

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.

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

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

After performing boehm titration using HCl,NaOH, Na₂CO₃, and NaHCO_3.  I want to know the formula to calculate functional groups.

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?

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

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?

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.

Is there a technological niche in pharmaceutical research that makes NQR or NMR the only measurement methods practically applicable?

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.

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

Email: ndesilva@uottawa.ca

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

Is there a technological niche in pharmaceutical research that makes NQR or NMR the only measurement methods practically applicable?

Analytical Chemistry

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,

For determination of water contents(moisture) spectrophotometrically.

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?

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.

Is sample cleanup not a part of sample preparation. Are there any examples sample cleanup that are not sample preparation in analytical chemistry?

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

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

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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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,

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,

application

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?

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!

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?

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?

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!

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.

Hello

Laboratory techniques of biological and analytical chemistry to investigate the anticancer properties of plant samples.

thanks

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,

I want to quantify the chromium in solution. I want to know whether atomic adsorption spectroscopy is better or UV vis spectrophotometer.

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.

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?

Chemical Informations

In the Column treatment of aqueous solution of Chromium Removal by Adsorption

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?

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

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!

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?

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

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

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?

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