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I came across a young Prosopis juliflora plant, which is highly invasive. What is the best method for collecting sand around the roots to study the potential
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The method for collecting sand around Prosopis juliflora roots to study allelopathic compound secretion is informed by established research in rhizosphere sampling and allelopathy studies. Key sources include:
  1. Rhizosphere Soil Method (RSM): This technique involves collecting soil directly from the rhizosphere to evaluate allelopathic activity. Fujii et al. (2005) and Karmegam et al. (2014) have utilized this method to detect allelochemicals in the root zone.
  2. Metabolite Profiling of Rhizosphere Soil: Studies have employed metabolite profiling to identify allelochemicals in rhizosphere soils. For instance, research on allelopathic rice varieties demonstrated the accumulation of specific metabolites in the rhizosphere, providing insights into allelopathic interactions.
  3. Extraction Techniques for Allelochemicals: Methods involving the extraction of allelochemicals from rhizosphere soil using solvents like methanol have been documented. For example, a study on the allelopathic effects of Saussurea lappa detailed the extraction of potential allelochemicals from rhizosphere soil samples.
  4. Standardized Protocols for Rhizosphere Sampling: Protocols for the independent extraction of bulk, rhizosphere, and rhizoplane soil fractions have been proposed to ensure consistency and accuracy in sampling.Such standardized methods facilitate the study of plant-microbe-soil interactions and allelopathic effects. These sources provide foundational methodologies for sampling rhizosphere soil and analyzing allelopathic compounds, which can be adapted to study Prosopis juliflora.
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Hi. Now I need to get the SMILES of ~1000 chemicals but I only have their names (e.g., ethanol). The only way I know to generate SMILES is from PubChem but I can only make 1 query at a time. Doing 1000 queries one by one is time-consuming. Is there any tool to batch convert chemical names to SMILES? Thank you!
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You can try open babel software 🙂
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I have a question about water samples taken from peatlands. What filter do you recommend (in terms of pore size) to filter this water (with a large amount of suspended substances)? My idea would be to filter it several times, but I'd have to start with a filter with a larger pore size and move on to a smaller one. Does anyone have any experience? Its subsequent use would be for chemical analysis in a photometer. Thank you
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Thank you all for your help. Matthew Wheal i do not have a centrifuge but i will try in my department. That might be a good strategy.
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I want to predict the reactions between my two desired inorganic chemical compounds. Can I? Is there any software or website for do this? Dear chemistry experts, please help me with this. Thank you for your response.
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You can predict reactions between inorganic compounds using tools like ChemReaX, AiZynthFinder, and Ansys Chemkin-Pro, which simulate and model chemical reactions. These software options allow you to explore potential reaction pathways based on your specific compounds.
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I am currently working on my bachelor thesis in the field of back injection molding of textiles made of polyester fibers. We have achieved quite good results with thermal treatments to restore the surface structure that has been flattened by the back injection process.
I would now be interested in the physical or chemical background that causes the fibers to straighten up again and the surface structure to return to its original state
Is it mainly relaxation processes or the entropic elastic behavior of polymers? Perhaps rearrangements or shifts also take place within the polymer chains.
I would be happy if someone has experience in this area and can perhaps even recommend some articles in which these causes have been researched.
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High temp. Need to dye polyester. And it is heated fast in warm condition. Perspiration is very low.
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Can data that includes less than values (below the limit of detection in chemical analysis) be used in ANOVA if the data is re-coded in some way? Perhaps using the actual detection limit or half of the detection limit is possible?
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I have seen many discussions about this topic, there's no real truth. Purists will tell you you cannot include those samples. However, from an application point of view, I would say you can. But my advice is to put yourself in the worst case scenario, so the conclusions are robust.
Let me explain: if the compound you are analysing is of interest, for example, antioxidants in food, and they are below LOD, I would put 0 instead, as it's the worst case scenario (this is, there's no antioxidants in your food). However, if it's cyanide in food, I would substitute values with the LOD, as it is the worst case scenario (there might be some cyanide in my food, even if it's low concentrations). In this way you will get the worst result possible, and cover your back.
However, remember that if you are in a continuous scale of concentrations, you also have the LOQ, but I'd still go with LOD in my example.
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I extracted protein from a roasted food sample using alkaline extraction followed by acid precipitation. Polyphenols were always coextracted since they were covalently bound with proteins during roasting and the formation of covalent bonds were irreversible. How can I know how abundant covalently-bound and noncovalently-bound polyphenols are in my protein extracts? I would greatly appreciate it if you could provide any suggestion or guidance.
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To proof that a small molecule is covalently bound to a polymer is very challenging. I was in similar situation when I tried to bind polyphenols covalently to chitosan. Generally, the polyphenols in your washing solution were either non-covalently bound or the covalent bond was cleaved during washing. The unremoved polyphenols are not necessarily bound covalently, as non-covalent interactions can still be too strong.
You could try to depolymerise your protein (e.g. by enzymatic hydrolysis) and then analyse the fragments (e.g. by LC-MS). If you find a fragment with the polyphenol bound covalently, you have a proof.
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Greetings
I've been searching for quite a while about Covalent organic framework (COF) and Porous organic polymer (POP) XRD pattern, how their xrd pattern should be and their differences.
But i could not find any specific findings.
some texts mentioned that COF xrd pattern should be sharp and pop should be broad. But ive seen so many COFs with broad PXRD pattern.
How can you distinguish between these two? How could you know that your product is POP or COF (etc. )?
Can somebody share their knowledge or mention a helpful Paper? Im so confused.
Thanks a lot.
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I have come across suggestions for optimizing the biosynthesis of silver nanoparticles to achieve smaller particles (<100 nm), indicating that the preparation of AgNO3 can influence the size of AgNP. What is the correct method for preparing a 1 mM AgNO3 solution, and are there any specific considerations I should be mindful of ?
I would greatly appreciate any insights or advice on these questions. Thank you in advance for your help.
Best regards,
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Michelle Darmawan The basic description above by Zbigniew Jońca is correct. I would add that all preparation should be in the dark (cover the containers with aluminum foil) as AgNO3 is easily decomposed by light to silver metal. The classic route of determining the concentration is by gravimetric means - precipitation of silver chloride with excess of sodium chloride.
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Methyl orange, phenopthalein etc.
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Dear Esteemed Colleague,
Greetings. I hope this message finds you well and thriving in your scientific endeavors. Your inquiry about the indicators used in various titrations and other chemical techniques is a fundamental aspect of analytical chemistry that plays a critical role in quantifying the concentration of unknown solutions. Indicators are substances that change color at a specific pH or in the presence of certain ions, providing a visual endpoint to titrations and other analytical methods. Below, I present a structured overview of common indicators and their applications in different types of titrations and chemical techniques.
Acid-Base Titrations
In acid-base titrations, indicators that change color in response to pH changes are used to identify the equivalence point.
  • Phenolphthalein: This indicator is commonly used in strong acid-strong base titrations. It changes color from colorless to pink in the pH range of 8.2 to 10.0, making it suitable for detecting the endpoint of these reactions.
  • Methyl Orange: Suitable for strong acid-weak base titrations, methyl orange transitions from red to yellow over the pH range of 3.1 to 4.4.
  • Bromothymol Blue: This indicator is used in weak acid-strong base titrations, changing color from yellow to blue over a pH range of 6.0 to 7.6.
Redox Titrations
Redox titrations involve the transfer of electrons between the analyte and titrant, and indicators for these titrations change color when they undergo oxidation or reduction.
  • Potassium Permanganate (KMnO₄): Acts as its own indicator in redox titrations, changing from purple to colorless when reduced.
  • Starch Solution: Used in iodometry, where it forms a deep blue complex with iodine. The disappearance of the blue color indicates the endpoint.
Complexometric Titrations
These titrations are based on the formation of a complex between the analyte and the titrant. Indicators for complexometric titrations change color when they bind to the metal ion or when the metal ion forms a complex with the titrant.
  • Eriochrome Black T: Commonly used in the titration of calcium and magnesium ions with EDTA, changing from wine-red to blue when all the metal ions have reacted.
  • Murexide: Used for titrating calcium in the presence of magnesium ions, changing from pink to purple as the endpoint is reached.
Precipitation Titrations
In precipitation titrations, the endpoint is detected by the formation of a precipitate or a change in the solubility of the precipitate.
  • Mohr’s Method using Chromate Ion (CrO₄²⁻): In argentometric titrations for chloride, bromide, or iodide, a potassium chromate indicator is used. The formation of a red precipitate of silver chromate indicates the endpoint.
Specialized Techniques
  • Fluorescent Indicators: Used in fluorescence spectroscopy, these indicators emit light when excited at a specific wavelength. The intensity or wavelength of the emitted light changes in response to the concentration of analyte, providing a quantitative measure.
  • pH Meter and Electrochemical Sensors: For precise measurements, especially when the color change of an indicator may be subjective, these devices provide a direct and accurate measure of the titration endpoint.
This overview encompasses the primary indicators and their applications across various titrations and chemical techniques. The choice of indicator is crucial for accurate and reliable analysis, and it should be selected based on the specific reaction conditions and the nature of the analyte and titrant.
I trust this detailed explanation will aid in your understanding and selection of appropriate indicators for your chemical analyses. Should you require further assistance or have more specific inquiries, please do not hesitate to reach out.
Warm regards.
Check out this protocol list; it might provide additional insights for resolving the issue.
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The accurate measurement of heavy metal concentrations in environmental samples, such as road dust, soil, and valley sediments, is essential for understanding environmental quality and potential risks. However, uncertainties arising from laboratory errors, including equipment limitations and human factors, can compromise the reliability of these measurements. This scientific discussion seeks to delve into these uncertainties, raising questions for which definitive answers are yet to be established.
-- How do different calibration methods impact the accuracy and precision of heavy metal concentration measurements in environmental samples?
-- To what extent does sample homogeneity affect heavy metal measurements, and how can variability within a sample be minimized?
-- Can statistical methods be developed to quantify and communicate the overall uncertainty associated with heavy metal concentration data?
-- How can technological advancements contribute to minimizing errors associated with instrumental analysis?
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This means that you want to have complete imaginable knowledge about the quality of measurement and analysis results and no doubts as to the correctness of the method of determining the total uncertainty of these results. Methodologically, this is a very correct approach and very forward-looking. Many books and even more articles have been written on each of these four problem groups that you distinguished. What has already been established and proposed on these topics certainly needs to be somehow organized and introduced into existing research methodologies, e.g. by creating recommendations and requirements. Research and government institutions do it. However, the crux of the matter is whether these recommendations and requirements are applied in research work, including in the work of analytical laboratories. Current requirements, e.g. regarding the obligation to provide uncertainty estimates of measurement and analytical results, are treated rather formally. This could change if the recipients of analytical information were dependent on the uncertainty values of specific results, and not only on average values, in their scientific conclusions and assessments of the state of the environment. But this is my point of view as an analytical chemist (retired). And as we know, the point of view depends on the point of sitting. Regards.
ZJ
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How do limitations in multi-element analysis impact the comprehensive understanding of heavy metal interactions in a given environment?
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Limitations in multi-element analysis can impact the comprehensive understanding of heavy metal interactions in a given environment in several ways.
1. **Incomplete Picture:** Multi-element analysis might not cover the entire spectrum of elements present in a given environment. Some crucial elements relevant to heavy metal interactions could be overlooked, leading to an incomplete understanding.
2. **Sensitivity and Detection Limits:** The sensitivity and detection limits of the analytical methods used can affect the accuracy of results. Some methods might not be sensitive enough to detect low concentrations of certain heavy metals, potentially underestimating their presence or impact.
3. **Interference Issues:** Interference from other elements or compounds in the sample can occur, leading to inaccuracies in measuring specific heavy metals. This can result in misinterpretation of interactions and relationships between different elements.
4. **Temporal and Spatial Variability:** Multi-element analysis might not capture temporal or spatial variations effectively. Heavy metal interactions can vary over time and space, and limitations in the analysis may hinder the ability to identify such patterns.
5. **Complex Speciation:** Heavy metals often exist in different chemical forms or species, each with unique behavior and reactivity. Some analytical techniques may struggle to differentiate between these species, limiting insights into their specific interactions.
Addressing these limitations may involve employing advanced analytical techniques, considering complementary methods, and ensuring a comprehensive sampling strategy. This enhances the accuracy and reliability of data, contributing to a more thorough understanding of heavy metal interactions in a given environment.
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Hello,
I was wondering, if you can store diluted quadrol (N,N,N′,N′-Tetrakis(2-Hydroxypropyl)ethylenediamine) in room temperature.
[Note:
The Quadrol was diluted with DI water, for the use of tissue clearing purpose (decolorisation of bones)]
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So, I am adding update from my experiments:
I did store the solution in room temperature for 1 day before using it to change solution (daily change according to protocol). In the end we didnt get expected flurosecence when imaging.
So, it would be best practice to prepare the solution before experiment as we got the fluroscence when we prepared the solution 30 minutues prior to performing experiments.
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I've been trying to make a solution out of DMF, Fmoc-osu and Glycine. For protection of glycine. I have a hot plate with a magnet and an ultrasonic machine. But nothing is working! I have also been trying to slowly add water to the mixture but Fmoc-osu precipitates as soon as i mix it. And it turns into a big mess. Please help me!
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DCM is a less polar solvent than DMF. So, it could dissolve Fmoc-Osu.
To glycine, you could try to dissolve in DMF.
Remember that the solubility depends on the quantity of solute and solvent.
Note:
-Consult in the bibliography the solubility of Glycine, Fmoc-OSU, and Fmoc-Gly-OH.
-Do not use water to form Fmoc-Gly-OH.
-Usually, Fmoc-amino acids are soluble in DMF, DMF/DCM, and DCM (in some cases).
-You could use ACN as a reaction solvent.
-Do not use water to form Fmoc-Gly-O-. Later you could use HCl/H2O to protonate Fmoc-Gly-O- to Fmoc-Gly-OH.
Follow the reaction by TLC of HPLC.
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I have a question about chemical analysis ICP sample preparation.
A 16g liquid sample was evaporated on a hot plate to obtain 0.9409g of salt.
Here, 4g of 2% HNO3 was added to completely dissolve the salt obtained from IPA, and analysis was performed.
At this time, the final concentration calculation must be multiplied by
Is the dilution factor 4.3042 correct? or is 0.2129 correct?
used to calculate
The density of the sample is 0.785g/ml
The density of 2% HNO3 is 1.01 g/ml.
Since the sample is reduced from 16 g to 0.8g, is 0.2129 correct considering the initial volume?
Or is 4.3042 correct by calculating the sample volume after digestion?
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I also wonder why it didn't use volumetric flasks in this procedure.
This procedure simply presented methods for weights.
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How can I calculate the molar ratio of Mg:P and N:P from the concentrations available in the attached table? Thank you
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To calculate the molar ratio of Mg:P and N:P from the given concentrations, we need to convert the concentrations from mg/L to mol/L.
The molar mass of Mg2+ is 24.31 g/mol, NH4+ is 18.04 g/mol and PO4 3- is 94.97 g/mol.
Let's take the first row of your table as an example:
So, the concentration of Mg2+ in mol/L is:
9363 mg/L * (1 g/1000 mg) * (1 mol/24.31 g) = 0.3852 mol/L
The concentration of NH4+ in mol/L is:
2138 mg/L * (1 g/1000 mg) * (1 mol/18.04 g) = 0.1185 mol/L
The concentration of PO4 3- in mol/L is:
18725 mg/L * (1 g/1000 mg) * (1 mol/94.97 g) = 0.1972 mol/L
The molar ratio of Mg:P is:
0.3852 mol/L / 0.1972 mol/L = 1.95
The molar ratio of N:P is:
0.1185 mol/L / 0.1972 mol/L = 0.60
I hope this helps!
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My question about the struvite precipitation (MgNH4PO4): Is the molar ratio of Mg:P the same as Mg: PO4, and N:P the same as NH4:PO4? Otherwise, Do I have to make any calculations when I convert from one form to another, like Mg:P to Mg: PO4? Thanks!
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In the case of struvite, the N and P refer exclusively to NH4 and PO4. So Mg:P == Mg:PO4 and N:P == NH4:PO4. The molar ratio is the amount of moles per liter. For struvite precipitatione the molar ratio of all 3 components is simply 1:1:1.
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If the Molar Ratio of struvite Mg2+:NH4+:PO4 is (1.6:1:1.2), how can I calculate the molar ratio of Mg:P and N:P? Thank you very much
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Struvite has the formula NH4MgPO4 x6H2O, so the N:Mg:P molar ratio is 1:1:1.
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I'm looking for something that can inhibit the reduction of FeIII for experimental research. Please help me if you know it.
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Oxidising agents,these chemicals enhance the oxidation of ferrous iron11 back to ferric ironfe111 by inhibiting its reduction eg,chlorine Cl2,H2O2,KMno4.Chelating agents can bind to ferric iron forming stable complexes ess prone to reduction EDTA,CITRIC ACID,OXALIC ACID.
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I want finding metallurgical length of high alloy steel in continuous casting.
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HI
In continuous casting of steel, metallurgical length (ML) is the distance between the exit from the mold and the point of full solidification of a steel slab,As ML depends on several factors like casting speed,steel grade,spray water cooling,machine design etc. it is difficult to evolve an
empirical formula solely based on chemical analysis of steel in this complex domain. But external factors by and large the same(keeping constant),through using normalization mathematical techniques i believe one can arrive at an empirical solution depending on steel grade.
thanks & regards,
g.sudhakar
phd(material engineering)
hcu.
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what is difference between living and non living ?life and death?#molecular concept
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As part of my ongoing research within the Energy-Impulse-Information-Tensor (EIIT) framework, I am delving into the intricate characteristics that distinguish living and non-living systems, as well as the profound concepts of life and death. This framework offers a holistic perspective to comprehend these concepts, viewing life as a complex system that harnesses energy, responds to impulses, processes information, and evolves within the fabric of spacetime.
1. **Energy**: Living organisms actively harness and convert energy to carry out various functions such as growth, reproduction, and maintenance. This energy is typically derived from food (in animals) or sunlight (in plants) and is used to drive biochemical reactions. In the EIIT framework, this energy utilization can be represented as a flow of energy within the tensor, which is absent in non-living entities. Non-living entities, like a rock or a molecule of water, may contain potential energy or kinetic energy due to their physical state, but they do not actively convert or use energy for processes like growth or reproduction.
2. **Impulse**: Living organisms respond to stimuli or impulses from their environment. This could range from a plant bending towards light to a human responding to a complex thought. In the EIIT framework, these responses can be represented as changes in the impulse components of the tensor. Non-living entities, on the other hand, do not respond to impulses in the same way. They may change state due to external forces, but these changes are not active responses and do not involve information processing.
3. **Information**: Living organisms process information. This is evident in the genetic information carried in DNA, which guides the growth and development of an organism. Additionally, organisms process information from their environment to make decisions. In the EIIT framework, this information processing can be represented as changes in the information components of the tensor. Non-living entities do not process information in the same way.
4. **Tensor**: The tensor in the EIIT framework represents the spacetime in which the living organisms exist and evolve. They are born, they grow, they reproduce, and they die. Over generations, populations of organisms evolve, driven by the forces of natural selection and genetic drift. Non-living entities, while existing within spacetime, do not evolve in the same way.
The boundary between living and non-living can be blurry, especially when we consider entities like viruses. Viruses exhibit some but not all characteristics of life. They contain genetic information and can evolve over time, but they do not have their own metabolism and cannot reproduce without a host cell. In the EIIT framework, viruses could be considered as systems that can process information and evolve over time, but do not independently utilize energy or respond to impulses.
As for the difference between life and death, in the EIIT framework, death could be considered as a state where the organism no longer processes energy, responds to impulses, or processes information. The system that was once a living organism no longer evolves over time in the same way. However, it's important to note that while the individual organism ceases to function, the energy and matter it was composed of continue to exist and transition into other forms and systems. This aligns with the principle of conservation of energy and the concept of information conservation, suggesting that while the specific configuration of energy and information that represented the living organism is gone, the energy and information themselves persist.
Regards,
Alessandro Rizzo
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I wanted to know the AoAC protocol for analysis of the p-anisidine value of fish oil.
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A paper that describes the methods in detail in the attachment is: 'Methods to determine the quality of acid oils and fatty acid distillates used in animal feeding' by Varona et al. 2021.
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Hi dear colleagues, I am a highway consultant and I have no knowledge to understand the results in the attached file, so please, I want to interpret the results of the chemical analysis of rock asphalt which I used in my research paper. with my regards
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Thank you very much my dear Horst for your answer.
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What type of chemical interaction can occur if more than 2 pollutants are present in the ambient air, which can affect the human health, especially in pregnant women?
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Air pollution is a major environmental health concern, especially for pregnant women. When more than two pollutants are present in the ambient air, chemical interactions can occur which can have serious consequences for human health.
One type of chemical interaction that can occur when multiple pollutants are present in the atmosphere is photochemical smog. This occurs when nitrogen oxides and volatile organic compounds (VOCs) react with sunlight to form ozone and other secondary pollutants. Ozone is a powerful oxidant that can irritate the respiratory system and cause inflammation of the lungs, leading to difficulty breathing, coughing and wheezing. It has also been linked to premature births and low birth weight in pregnant women.
Another type of chemical interaction that can occur when multiple pollutants are present in the atmosphere is acid rain. This occurs when sulfur dioxide and nitrogen oxides react with water vapor in the atmosphere to form sulfuric acid and nitric acid. These acids then fall back to earth as rain or snow, causing damage to plants, animals, buildings and other structures. Acid rain has been linked to an increased risk of preterm delivery among pregnant women due to its ability to reduce air quality by increasing levels of particulate matter (PM).
Finally, another type of chemical interaction that can occur when multiple pollutants are present in the atmosphere is secondary particulate matter (PM). This occurs when primary PM particles such as dust or soot react with other gases such as sulfur dioxide or nitrogen oxides in the atmosphere to form secondary PM particles such as sulfates or nitrates. These secondary PM particles are smaller than primary PM particles but still pose a health risk due to their ability to penetrate deep into the lungs where they can cause inflammation and irritation leading to difficulty breathing, coughing and wheezing. Pregnant women exposed to high levels of secondary PM have been found to be at an increased risk of preterm delivery.
To wrap it up, chemical interactions between multiple pollutants present in the ambient air can have serious consequences for human health, particularly for pregnant women who may be exposed over longer periods of time than other individuals. It is therefore important that steps are taken by governments around the world to reduce air pollution levels through measures such as improved vehicle emissions standards or stricter regulations on industrial emissions so that we can protect our environment and ensure better health outcomes for all individuals including pregnant women.
Sources:
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Quantification of EDX spectra of Al-based casting alloys it was found certain intensity of Zr (up to 0.7 wt. percent) whereas the chemical analysis showed only very little Zr content (0.05). EDX were performed using Talos 120 TEM. Any Zr-enriched precipitates were not observed. I am looking for an answer why Zr intercity appeared in the aluminium matrix whereas it can't be. Many thanks in advance
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Dear Mykhalenkov, I will be performing the TEM analysis of as-cast Al alloys soon and will let you know if I encounter this problem.
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I am searching for papers to get an overview of different approaches on longitudinal sampling strategies. For me, it would be important to know how they deal with wastewater treatment plants, inlets from other streams and urban areas. I want to identify differences in chemical pollution within one stream.
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There are several papers and studies that have addressed longitudinal sampling strategies for assessing chemical pollution in aquatic environments, including freshwater streams and rivers. Some of these studies focus specifically on the impact of wastewater treatment plants, inlets from other streams, and urban areas on chemical pollution levels.
Here are some studies you might find relevant to your research:
  1. "Longitudinal Sampling for Monitoring Trace Metal Concentrations in Urban Streams" (B. A. Kimball and D. J. Weston, 1999)
  2. "Long-term monitoring of persistent organic pollutants in a river network: temporal trends and spatial differences" (A. Covaci, F. Schepens, K. J. Chalew, and P. F. K. Sparreboom, 2005)
  3. "Longitudinal Sampling for Evaluating Changes in Mercury Concentrations in River Sediments" (B. A. Kimball and J. M. Omernik, 2003)
  4. "Longitudinal study of persistent organic pollutants in the European Arctic rivers and coastal waters" (A. Covaci, F. Schepens, P. F. K. Sparreboom, R. C. Thompson, and K. J. Chalew, 2004)
You can access these studies through academic search engines such as Google Scholar or Web of Science. Additionally, you may want to consider reaching out to researchers in the field to see if they have access to additional resources or if they know of any recent studies on this topic.
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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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The demand for ready- to- eat food is increasing worldwide. Fresh foods are facing challenges in terms of their limited shelf life, association with food borne diseases and outbreak. This results in commercial pressure from consumers on the use of synthetic chemicals as food preservatives. A wide range of synthetic additives are used as preservatives in food industries in order to increase their shelf life and inhibit bacterial growth. However, use of these synthetic chemicals is causing health threats to consumers. Plant antimicrobials are getting into potential interest as a good alternative over synthetic food additives. Limited research has been done on the use of pine antimicrobials in food industry. This research will focus on the use of chemical analysis by qualitative and quantitative techniques in extracting plant antimicrobials (the phytochemicals) from Pinus caribaea needles var. hondurensis, in order to shed light on its potential usage in food industry as a natural food preserving additive. Pinus caribaea needles will be collected from Fiji Pines forest stations (Lololo, Ra, Nabou, Nai, Bua, and Maduata forest stations, and nurseries: Ra, Nabou, and Nadi) of different ages (3 weeks- 6 months, and 5, 10, 15, and 20 years) of the tree. Chemical analysis will be conducted via qualitative (use of chemicals), and quantitative (UV Spectrometry and Gas chromatography, Gas chromatography/ Mass spectrometry) techniques. The effect of the age of the pine needles and its environmental factors on the quantity of phytochemical extraction will be considered. This finding will assist in potential usage of plant antimicrobials extracted from Pinus caribaea needles var. hondurensis in food industry as a food ingredient, and further in- depth research can be continued on this limited research present in literature.
looking for collaborations in writing review papers and ideas in doing this project. Thankyou
thank you
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What "health threats" are caused by current food preservatives and do you plan to address the human safety of pine needle extracts ?
Please be aware of relevant reports of pine needle extracts as potential food preservatives https://scholar.google.com/scholar?hl=en&as_sdt=0,10&q=pine+needle+extracts+as+food+preservative
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What are the factors that increase the thickness of the chemical coating with nickel. In Standard about 20 micrometers. I have to aim for a coating thickness of 80-100 micrometer. Any suggestions
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Use the electrolysis method. Increase the electrolysis time or the concentration of the electrolyte solution.
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Hello friends
Iam doing a project based on chemical analysis of Pinus Caribaea leaves and the potential uses for tea consumption
Looking for some collaboration for writing review papers and project
Vinaka
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Hi Anshiu,
I am interested to work with you on this review paper. My email: kahchoon.15@yahoo.com
Feel free to check this out:
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I want to check the presence of cadmium ions in a complex by doing a Chemical analysis, kindly suggest a method.
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Well, it depends on the resources you have.
At the undergraduate level, we have taken the cadmium salt in dil.HCl and pass hydrogen Sulphide (can be generated by slowly adding dil.HCl into ZnS). Yellow precipitate indicates the presence of cadmium.
Metal coordinating compounds like Dithioxamide can also help, but I don't've experience on this.
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Hello,
I am looking for chitin reference material for chemical analysis. I found this reference material:
However, I am looking for a second one similar to this one. Does anyone know of a producer/company selling those?
Clement
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Hi Clement,
You may make an inquiry at Alfa Chemistry, they offer kinds of good-quality materials.
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The idea is to relate the analysis with different urbanization indicators and land uses.
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soil is part of the environment. but the chemical analysis of soil to detect soil pollution is a part of environmental chemistry.
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Hi there,
I'm currently doing research on the compsition of the liquid phase generated by thermal degradation of Poly(methyl methacrylate) (PMMA).
In my group we are especally interested in finding the monomer methyl methacrylate (MMA).
But from literature I have kind of a clue what else I can expect to be in the mixture,
like methyl propionate, methyl isobutyrate and other carbonyl-, ester- and diester-compounds.
Their boiling points should range between 50 °C and 270 °C and I consider them themally stabel.
Now I thouhgt on first analyzing the samples with GC-MS, because the GC allows to seperate the different compunds and MS will help me to characterize those compounds.
The problem is, that I've never done GC-MS before and I'm a bit puzzled if I have to dissolve my sampels or if I can probe them directly?
Is there a benefit in using a solvent?
And what requiremnets should a solvent fullfil, apart form dissolving my sample and beeing thermally stable, especally regarding the boiling point?
Thanks already for your suggestions!
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Hello Christoph
You have already mentioned the most important criterion: all analytes should dissolve in the solvent without any problems. I think methanol would be a good choice. Since GC-MS systems usually have a high sensitivity, it makes sense to dilute the sample. You can determine the dilution factor yourself. I would prefer a split injection at this point, since residual monomers are mostly volatile and can therefore not be focused well at the column head. The split ratio can easily be adjusted to the concentration of the injection solution at this point (high concentration = high split ratio). The temperature program is column-dependent. Since I don't know which phase is installed in your GC, I can't say much about it, but optimizing a separation is not big a problem.
In my experience the mass range of the MS is optimal with 35-350 u, no residual air peaks are recorded and the high siloxane masses of the column bleed are also not recorded. Methanol as solvent has the advantage that it is also "invisible" with mass 32.
Otherwise, additional information would be useful, e.g. which instrument (manufacturer), which column, sample quantities, autosampler, etc.
If you have more questions I will look for helpful answers.
Good luck and many greetings from Krefeld
Joachim Horst
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It is known that essential oil yielding plants belong to some specific families such as Lamiaceae, Lauraceae and so on. Is there any specific criteria to identify such oil yielding plants in field without chemical analysis? For survey of such plants?
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Oil-yielding plants can be identified in the field by their aroma. One can rub a plant's leaves or flowers in his/her hands and sense if they have any kind of fragrance. If yes, then it must be an aromatic plant. To confirm it further, try Google Lens. If you identify the plant's name, then the answer is clear. To obtain oil yield, plant material can be hydro distilled or other methods can be done as per convenience to extract essential oil.
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FT- IR can be used as an advanced analyser for chemical analysis,
So which parameters do I detect for the chemical analysis of mustard oils?
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FTIR spectroscopy is mainly used for the analysis of different oils to check for the presence of any foreign or illegal additives. Sanaullah Mazumdar
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Hi Everyon,
We are using ionic deposition to coat a mix of metals on a plate. We like to map the metal compositions on different parts of the plate or at least before they hit the plat (ionic form). What’s the best way to do this without taking off the coating from the plate as we want it to stay intact…
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Dear Hamidreza Jalilian,
I think there could be two techniques.
One would be SEM-EDX. With this method, you can detect the X-rays coming from the sample surface (penetration depth depending on acceleration voltage of the electron beam). This method has a spatial resolution down to µm. And with this you can usually create so-called element maps.
The other one would be XPS. Here, you use X-rays to induce photoelectron formation in the material. Penetration depth is also depending on X-ray beam energy. In theory you could scan different areas in XPS, but I am not sure how to do this technically.
Hope this helps
Kind regards
Lucas Warmuth
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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 am trying to obtain chitin by a chemical method. After deproteinization and demineralization processes, the powder obtained after each step is too alkaline or acidic respectively. Then, I spend a lot of deionized water during washing power. Is it acceptable to add something to the deionized water to get neutrality faster?
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Think Rasweefli has developed a better process than Khalifa Al Shaqsi
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I know magnetic separation can separate Fe, γ-Fe2O3, Fe3O4. But I don't know how to get Fe powders from residues. Someone say sodium pyrophosphate could remove γ-Fe2O3, Fe3O4, is it a feasible method ? Or other better method?
Thanks very much for your answers!
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Hi you should dissolve your target iron oxides, though the possibility exists that your elemental iron could also be attacked.
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Excessive use of chemicals in agriculture results in contamination of products with high levels of chemical residues.
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In response to "What health problems should be faced? a full argumentation has been already developed by Prem Baboo . In response to "How do chemical residue products harm consumer health?" the route of chemical residue products is recognized by the transportation of these embodied (attached to vegetables and fruits) quantities of applied chemicals directly to the consumer plate through the food chain/local food webs. Subsequently, a high portion of chemicals' removal is recommended at cleaning up and gently rub of vegetables and fruits while holding them under plain running water. In field measures include the biological and the organic farming, enabling a healthier sustainable food production while minimizing external inputs of chemicals and environmental impacts on the agricultural fields.
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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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I have been trying to detect a compound using a GC-MS system, but the probability is not high enough thanks to a lot of other compounds with similar mass spectra in NIST library. The only way I can think of to distinguish among them is retention index since some of those compounds are hard to obtain. I noticed that temperature programmed retention indices are not really system independent.
Therefore, under what conditions beside same stationary phases (DB-5MS in my case) can I make a comparison? Should the temperature programs and column lengths strictly match?
Thanks in advance for any advice.
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The database of compounds in Retention Index (RI) are linked to the columnn phase.
The brand of your column may change the RI a little bit from one to another. So for more precision of the identifcation, it's important to have the same column brand as the one used to build the database of compounds in RI.
Sometimes, the RI may change a bit as well depending on the injected products chemistry in this column.
But the indices are not linked to the temperature programs since you have to use the same method for the analysed chromatogram (e.g. sample) and your chromatogram of indices reference (alkanes, Ethyl Ester etc.). The retention time will move the same way on both chromatogram allowing to convert from RT to RI correctly whatever the temperature program and the column size (but obviously the shorter the harder the compounds identification because of the coelutions, but still can be identified with the database of compounds in RI...).
WARNING: the temperature program has to be linear during the elution of all compounds (you can have a step at the beginning and at the end).
To improve the identification, the best configuration is to have two columns (e.g. polar, non polar) and to cross the results between the two database. This way even you are at +-20 around the RI of your compounds (needed if you have to deal with a different column brand comparing to the database you own or find online), only the common compound(s) will show up in the result of the crossing of the two lists (polar, non polar) from the two database.
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Q1: In many articles on jadeite and jadeitite(Shi 2008,CÁRDENAS-PÁRRAGA2021, Meng 2016, Abduriyim2017, et al.), scholars draw spider diagram based on trace element data and REE from LA-CIP-MS. But the number of elements in the horizontal coordinate is often different. What is the principle on which this is selected?
Q2: When some of the results of the test are below the detection limit(bdl) , or the corresponding elements are not detected (nd), how should they be reflected in the diagram?
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Trace element abundance plots (spidergrams) are used to illustrate the rare earth element or mantle incompatible trace element contents of a sample. The order of trace elements is usually shown in the order of decreasing ionic radii. In the case of the REE, where the lighter elements such as La have the larger ionic radii (due to the lanthanide contraction with higher atomic numbers), the LREE are shown on the left and the HREE on the right part of the spidergram. Elements concentrations below detection limit cannot be plotted. The computer program plotting the spidergram usually interpolates their values between its neighboring elements.
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Hello all,
I am preparing a compilation file for doing MESMER calculations but I am having an issue. I am running some g08 calculations with acetyl and it seems like the transition state from for going to the RO2 to QOOH is unstable as the difference between the target energy and the calculated energy differs by about 0.1 - 1.1. There is too big a difference in the energy barriers between the RO2 and QOOH, but all other energies for the stationary points in the channels are comparative to the expected value. The IRC from the obtained transition state gave a significantly high "jump" in the potential energy graph. Would anyone happen to know what is going on?
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By unstable, I mean that the SCF Done is coming out too low than the expected. The target energy is coming from a the Ethanal+OH/O2 system that has been studied in literature that we are trying to emulate. The unit of measurement is in Hartrees
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What is the approximate COD value of 50 ppm aqueous Acetaminophen solution (C8H9NO2, Mol wt 151.163 g/mol)?
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Aarif Shah, If the COD analysis is the standard one with chromate in acid I think the standard balanced reaction will be: C8H9NO2 + 9O2 +H+ -> 8CO2 + 4H2O + NH4+
The combusting reaction suggested by Kai Bester:
C8H9NO2 + 11O2 -> 8CO2 + 2½H2O + NO3- + H+ in my opinion overestimate the COD as typically chromic acid is not able to oxidize N(-III) in the standard analysishttps://en.wikipedia.org/wiki/Chemical_oxygen_demand.
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Nbc-Ni Cermets samples are sintered in a vacuum sintering furnace at @1450 degrees. The Samples were placed in the Alumina Piece as shown in the attached pictures. after sintering the color of the alumina piece changes to blue as shown in the picture. what can be the reason behind it? Thanks
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Dear Abdul,
I never worked with these materials but they are high melting point-based, so I believe the influence will be minor. I recommend you'll measure Al content prior to and after the heat treatment of your samples.
Good luck.
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chemical analysis
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Wang Yun Google is you friend. Properties are identical to zirconia with which it is intimately found. Wiki gives you:
"Hafnium(IV) oxide is quite inert. It reacts with strong acids such as concentrated sulfuric acid and with strong bases. It dissolves slowly in hydrofluoric acid to give fluorohafnate anions. At elevated temperatures, it reacts with chlorine in the presence of graphite or carbon tetrachloride to give hafnium tetrachloride"
It is separated from ZrO2 with difficulty.
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I prepared a solution of 100ml THF, 20ml tert-butoxide in THF and 4ml 1,3-propane sultone. To this, I added 11gm of my nanoparticles. Once I receive the result of ICP-AES, how should I calculate the number of particles present? How should I check whether I have achieved proper functionalization of my sample or not?
I have sent 1gm of sample powder for analysis.
Any suggestions will be much appreciated.
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You should take the density for this material, calculate the amount of the material in one spherical particle, calculate the mass of a particle. After the calculation of the desired concentration, you should take it as a total mass for this component. Take this mass and devide it by the mass of a particle. This will be a very-very rough estimation, but I cannot offer more acording to these conditions.
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Rare-earth halide/Rare-earth oxyhalide + alkali metal oxide = ?
For example, GdX3 + Li2O = ? at high temperature (~1300 C)
Please provide reference on your answer.
Thanks in advance
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For this type of question I would first get an idea of what could be expected by looking up the free energy of formation of the compounds in question at room temperature, in the humble Handbook of Chemistry and Physics or Lange's Handbook of Chemistry. Write a balanced equation and sum up the free energies of formation with the right algebraic signs. You'll find out that Li has a huge preference for the halide compounds compared to the lanthanides - tens of Kcal/mol per mole of bonds (M-X or M-O-).
Now for the 1300C part: I don't have this reference available with me, but it's likely that you can find you need for at least some of the compounds in
I. Barin, O. Knacke: Thermochemical Properties of Inorganic Substances. Springer-Verlag, Berlin — Verlag Stahleisen, Düsseldorf 1973 (and supplements published since).
Another good source for high temperatures is JANAF's Thermochemical Tables, but that is more restricted in terms of the compounds included, and I think it doesn't have what you need.
Chances are you'll find that the direction of these particular reactions at 1300C is the same as at room temperature. As long as only condensed phases are involved (solids and liquids), the change in molar heat capacity with temperature doesn't vary enough between the different compounds involved to lead to a sign reversal in the free energy of reaction. If the free energy of reaction at room temperature were, say, an order of magnitude smaller it would be much more difficult for me to make a prediction and I would need the actual 1300C data.
Finally, do not get discouraged if you find free energy of formation data just for a couple of trivalent lanthanides. The trend will be similar for the others, with the caveat that the degree of preference for bonding to oxide over halide tends to grow as you advance from the lighter lanthanides (La, Nd) to the heavier ones. Yttrium, of course, is similar roughly to dysprosium and holmium, and being much more common you may find data for it.
Best regards,
Emanuel Cooper
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I was unable to perform the sampling and analysis for 40 surface water and 20 groundwater samples, so I hired an in-country consultant firm to do it. The results that they returned were difficult to interpret and had extremely high levels of iron and manganese. I spoke with a former professor and he expressed concern from his long career of working in SE Asia that the subcontractor/lab might not have filtered the samples. How can I know that the results are for the water and not the particulates?
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Dear Liz Kendall . Do the analysis of the same samples at different labs then compare the results. See which results are the same and exclude the results that are far way from the comparable results. Then you can judge which lab is trusted and which is not. Best wishes.
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I measured the particles size (<1000 nm) in aqueous solutions by DLS, but I found these particles can aggregate spontaneously, and it seems that smaller particles aggregate more.
I sincerely hope you can help me explain this phenomena.
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Dear all, Ostwald ripening may be behind such aggregation, this mostly happen when surface free energy in too high, i.e. fine nanoparticles with high specific surface area, so coarsening of nanoparticles is the mean by which size is increased and specific surface area is reduced. Small nanoparticles are more prone to aggregation because of their high surface free energy which for stability reason should be reduced, and for this purpose protective colloids techniques have been developped to prolonge stability time. My Regards
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We have now over 350 000 chemicals and mixtures of chemicals registered for production and use, and more are developed constantly. How can we speed up their assessment for safety, to erase the backlog of unexamined ones?
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Approaches for read-across can provide a practical alternative for safety assessment of compounds which have similar structures or result in the same major metabolites.
"Read-across exploits information on structurally related (similar) analogues to derive hypotheses about the activity of the new chemical and hence predict its toxicity without experimental testing."
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Hello, I have some doubts about DLS measuring the size of the nanoparticles.I hope to get answers from you.
I measure TiO2-NPs(60nm,commercialization ) in 0.01M PBS. But Instrument prompt “sample too polydisperse for cumulant analysis” and “sample too polydisperse for distribution analysis” .Correlation Functions show the picture as followed. Why does this happen and how to avoid it ?
All dispersions were filtered with 0.45um filter. Ultrasonic dispersionwas used.
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one should be careful - it does not make sense to treat (change) the sample until 'it can be measured'. The useful information is what is the sample in original state and after defined steps of treatment.
If you start with a powder it is already strongly aggregated/agglomerated. While agglomeration might be reversed, e.g. by sonication, reversal of aggregation is almost impossible.
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Hi, could you recommend a software compatible with spectrophotometry from various brands?
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P.S: I wash the column with water and methanol when I open and close the HPLC system.
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What are the benefits and the disadvantages of those?
what industries use those item beside Textile and paints?
does it have any other uses beside as dispersing agent?
which one gives more water resistance in paint and why?
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A lot of generic questions including judgements. From my side I can contribute as follows. Neutralizing PAA with NH4+ seems to me akward. I could imagine that this leads to protonated PAA (without any charge anymore) and NH3. From physical-chemical point of few, the behavior of NaPAA seems to be a bit more predictable.
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Palmyrah fruit pulp has a bitter taste due to this saponin, so I have to remove the saponin with a cheaper method which can be applicable to the fruit industry.
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add naringinase enzyme
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Where can I find alagebrium I want to use it in my research ?
And astaxanthin also and is it expensive?
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Hello.
Take alagebrium for example, you can search it on google scholar (or others) and get some articles about it. I picked up one as below.
Am J Transl Res. 2019; 11(3): 1569–1580.; PMCID: PMC6456531
In this article, they mentioned that "......AGEs inhibitor ALT-711 (20 μg/mL; MedChemExpress, China) was added......". So you can turn to "MedChemExpress" to see if the price and distance are ideal or not. If not, turn to other papers.
It has to be mentioned that, you can go to https://scifinder.cas.org/scifinder. Using substance identifier will easily lead you to what you want, though I had not bought through this way.
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Try to do a research for making a physical or chemical reaction in CO2 to transform it to Carbon and Diamond. What is the possibility for that ?
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The question in itself talks about the exciting opportunities to drive the interest of the researchers. As of now, the available processes are complex and do require sophisticated infrastructure. A perfect catalyst may solve this issue.
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Why the DNA sample that recovered from urea polyacrylamide gel electrophoresis become iced/solid during the ethanol preparation ?
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The critical step is removing the acrylamide after elution. After cutting the gel slice do not led it drying, keep it in the elution buffer and cut it in small fragments without crushing.
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I would like to analyse monocarboxylic acids higher than C20 (at least up to C30), but I cannot find a company for buying them. I prefer a mixture of more acids in an organic solvent but it can be solid standards. Thank you.
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Hi Kamil,
You may make an inquiry at Alfa Chemistry, they offer kinds of good-quality chemicals.
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say, when we take a simple titration of any compound to induce some change and study the change what we can see the change if it is faster change in the optical parameter or change in absorption or energy change or when we do its electro chemical analysis the changed species will be faster response as its electron transfer, what will be faster ? or both the methodologies will be different in kinetics due to different technical aspects and parameters? optical corresponds to the technique spectrophotometric methods . and more elaboratively from which technique we can get better electron transfer kinetics or the accurate degree of minimal observable change.
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Optical changes are faster
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Different results were obtained from both
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There is no simple answer to this question. So you are dealing with a situation where the results of the analysis of the elemental composition of a specific cement sample obtained by different methods differ significantly. Why do you think the differences are significant? Do these results have assigned uncertainty values? And would you like to know which method is generally more accurate? Theoretically, classical methods are more accurate, because XRF techniques are calibrated and checked with reference materials, the certified values of which were established mainly by classical methods. In a case like yours, this can only be checked with additional analyzes performed by another analyst in a specialized laboratory.
ZJ
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Dear researchers,
I do not know how to use Origin software to draw a graph with very high (3000) and very low (100) numbers on the vertical axis. Could you please help me?
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Dear all,
Would you please help me to find out the best approach to calculate the potential heat recovery from exothermic reactions? Are there any good references to introduce me in order to enhance my knowledge over recovering heat from exothermic reactions. I will be very thankful for your helpful advice and recommendations.
Thanks in Advance for your kind considerations.
Yours faithfully,
Nashmin
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There are a number of methods for measuring the heat of an exothermic reaction. But in any case, not so simple equipment is needed. One option is to use a bomb calorimeter (see https://en.wikipedia.org/wiki/Calorimeter). An example can be found here https://arc.aiaa.org/doi/abs/10.2514/3.25795?journalCode=jsr.
Another option is to find a laboratory that performs thermogravimetric analysis (TGA, see, for example, https://link.springer.com/chapter/10.1007/978-3-030-11599-9_7) or differential scanning calorimetry (DSC). From the processing of these data, one can obtain the heat of reaction. An example can be found here Kong Y., Hay J. N. The measurement of the crystallinity of polymers by DSC //Polymer. 2002. V. 43. Iss. 14. Pp. 3873-3878 or here Faleeva J. M. et al. Exothermic effect during torrefaction //Journal of Physics: Conference Series. IOP Publishing, 2018. V. 946. Iss. 1. Art. # 012033; Zaichenko V. M. et al. Thermal effects during biomass torrefaction //Solid Fuel Chemistry. 2020. V. 54. Iss. 4. pp. 228-231.
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C1s peak at 284.8 corresponding to Adventitious Carbon is a reference for the X-ray photoelectron spectroscopy (XPS. However, when using carbon-based support, say Vulcan carbon (rich in graphitic carbon), r-GO and GO for deposition of active catalyst.
The C1s peak in these cases will be dominated by sp2 carbons, not by Adventitious Carbon.
How to calibrate the XPS data in that case?
How to account for the charging problem?
Thanks in advance
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As Jurgen states, the vulcan carbon should have enough conductivity. If using a monochromatic XPS system then analyse without the charge neutraliser on and ensure the carbon is in contact with the spectrometer (e.g. pressed in to a metallic well on the sample bar), then you shouldn't have an issue. The sp2 carbon will be ~ 284.5 eV depending on how well your spectrometer is calibrated.
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Hi, We want to measure the radiation patterns of an implantable antenna. The mimicking gel that we are using has different conductivity than that used for simulations. We want to increase the conductivity of our mimicking gel without increasing the permittivity.
We know that adding sugar and salt will increase the conductivity. However, it decreases the permittivity!!!
Any suggestions?
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I don't have an answer, but a warning. In microwaves and RF it is the refractive index that matters. The real part determines the wavelength and the imaginary part the losses. The refractive index is the square root of the relative permittivity - ignoring permeability. When you take the square root of the complex relative permittivity, it halves the angle of the complex number as well as taking the square root of its length, and the imaginary term in the permittivity, which will be changed by changing the conductivity, will result in the real part of the refractive index being changed. If you want the real part of the refractive index to be unchanged, it may be necessary that the real part of the permittivity falls a bit if the conductivity increases. It is worth working out the numbers for the real and imaginary refractive index you want and what permittivity that results in.
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I am trying to analyse a certain material in a certain food product via HPLC. However, I crossed problems and tried to correct them but problem goes on.
 After i see baseline in HPLC, i put standards and then my sample vial.
My sample showed a peak more area than standard peaks area. As first correction, i sent more concentration standard to HPLC column, Then i recognised that my sample peak got increase. As i increase standard concentration, peak of sample getting increase
As second application, i tried diluting sample concentration. Firstly i sent standards then i applied samples which are different concentration. But it didnt work well. For each diluted sample i read two times but machine didnt read peak of sample accurately. While first parallel showed a peak, second parallel didnt show any peak. 
I cleaned HPLC column with mobile phase but it didnt change results. After cleaning of column i get a baseline but while reading samples, it doesnt show peak each time.
What is your recommendation for this problem?  
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I have no specific experience, but it sounds like you have a source of urinary acid , like an ester. At that pH this ester is breaking apart at the ester bridge giving you more urinary acid than expected. Try increasing the pH of the mobile phase to 3, then 4, then 5 and check your peak.
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Hello everyone
Based on the calculation of the enthalpy peaks of crystallization and melting of the DSC test of the provided PLA sample, the crystallinity degree is 12.2%. I don't know if this achieved percentage is logical or not. Kindly, take a look at the attached result and tell me if my calculation was right or not.
P.s = the cooling rate was 30˚ C/min.
Best regards.
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Dear Milad, thank you for asking this very interesting technical question concerning the crystallinity of PLA (= poly(lactic acid)). In this context please have a look at the following useful research article which mght help you in your analysis:
Crystallization of PLA-based Materials
This paper has been posted on RG as public full text, so that it can be freely downloaded as pdf file. Also please go through the following relevant reference:
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Is it possible that the mechanism of stress corrosion cracking(SCC), in PLA is related to factors such as the crystallinity of the polymer, the pH of simulated body fluid, and the magnitude of the applied load?
Best regards.
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Dear Milad
The phenomenon of SCC normally occurrs in polycrystalline metallic alloys that are succeptible to a combined of corrosion,i.e.,chemical dissolution, and a tensile deformation. Therefore,the possibility of SCC of PLA is slim to impossible .
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Hello everyone
I use a metal powder as the filler to a thermoplastic polymer matrix. Therefore, I wonder if there are any changes such as the molecular weight distribution, occurring in the structure by adding the filler metal powder?
My regards.
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Dear,
Some pigments can cause property modifications. I have tested PLA with different colors, and they have different tensile strengths.
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Hello everyone
I have done a DSC test on the poly-lactic acid by Mettler DSC set-up. As the result shows, there are three endothermic peaks in the red curve that I marked by the black color. It is obvious that peak number one belongs to the glass transition temperature, and peak number three is the melting temperature, but I don't know exactly what is the type of peak number two. I have this concern that the second peak might be the effect of impurity or a metastable modification in the polymer tested.
Any guidance, suggestion, or opinion would be helpful.
Best regards.
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For a polymer thermal analysis of the type of sample you have, you can first examine the TGA thermogram and identify the temperature range your polymer is stable. T hen, use DSC to heat to the temperature you are certain that your polymer is not degrading. Then, stop heating and cool the sample slowly in the DSC instrument, and start the heating cycle again. Any of those phenomena that are not reproducible, such as polymerization exotherm, impurity evaporation, anthalpic relaxation, etc will disappear in the second heating curve. Although impurity, including residual water, is a possibility for the second peak, what I am concerned is the slight exothermic event right before endothermic event that followed. Impurities usually do not show that. Have you made sure that you do not have residual lactic acid that did not polymerize?