Chemical Analysis - Science topic

As that is a calculation of colligative properties of non-electrolytes it may be a matter of deciding which is the "solvent" and which are the solutes. As the freezing point depression ('C/mole solute) is known for each of them, a comparison (or convergence) of the calculated freezing point for any given mixture could be made.

Think Rasweefli has developed a better process than Khalifa Al Shaqsi

Hi you should dissolve your target iron oxides, though the possibility exists that your elemental iron could also be attacked.

The numerous negative health effects that have been associated with chemical pesticides include, among other effects, dermatological, gastrointestinal, neurological, carcinogenic, respiratory, reproductive, and endocrine effects. Chemical fertilizer overuse can contribute to soil acidification and soil crust, thereby reducing the content of organic matter, humus content, beneficial species, stunting plant growth, altering the pH of the soil, growing pests, and even leading to the release of greenhouse gases. Farmers in developing countries are experiencing, either short-term or long-term, health effects from exposures to agricultural chemicals, including severe symptoms (e.g. headaches, skin rashes, eye irritations) and some chronic effects (e.g. cancer, endocrine disruption, birth defects).

Dear Franklin Uriel Parás Hernández, both degradation and crystallization are behind the change in color aspect. My Regards

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.

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.

Dear Jürgen Weippert

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

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 + NH_4⁺

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 analysis^{https://en.wikipedia.org/wiki/Chemical_oxygen_demand}.

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.

Wang Yun Google is you friend. Properties are identical to zirconia with which it is intimately found. Wiki gives you:

It is separated from ZrO₂ with difficulty.

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.

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

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.

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

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."

Another reason could be the ionic strength of your PBS solution which may generate "Debye screening effects". This essentially means that electrostatic stabilization of your particles is decreased, leading to agglomeration and the apparent polydispersity.

See here for more info: https://www.materials-talks.com/debye-screening-how-it-affects-zeta-potential/

Dear Paolo Pelini Kindly visit..

Kind;ly visit..

Hridoy Saha

Using the XRD method, you can determine which copper oxide (nanophase) you have on the surface is bivalent or monovalent.

Using the EDS method, you will determine the ratio of carbon and copper content in nanoparticles

With the FTIR method, you can determine how copper atoms and ions are distributed and with which functional group they are bonded on the surface.

By method AFM you can see how the surface layer on nanoparticles changes and can determine its thickness and change.

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.

add naringinase enzyme

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.

Osman Ali Sadek Ibrahim and Frank T. Edelmann ,

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.

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.

Hi Kamil,

You may make an inquiry at Alfa Chemistry, they offer kinds of good-quality chemicals.

Optical changes are faster

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

Dear Foroogh Khodadadi

These tutorials might be useful, have a look:

1. https://www.youtube.com/watch?v=twciwBq-ziY

2. https://www.youtube.com/watch?v=oIqqwovfFfU

3. https://www.youtube.com/watch?v=HSFaPd2BSRw

4. https://www.youtube.com/watch?v=srz_YBjU02I

Kind Regards

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.

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.

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.

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.

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:

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 .

Dear,

Some pigments can cause property modifications. I have tested PLA with different colors, and they have different tensile strengths.

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?

@Ntombi Ncube, very helpful. Thanks

Dear https://www.researchgate.net/profile/Aarif-Shah-2 , Just ensure that DAD detector is working on VW ( Variable Wavelength ) priciple but UV detector is working on Lambert Beers law principle entirely different . You are again requested to calculate manually % RSD between two wavelengths ( not more than 2 % ) .Please go through the deatail - https://www.ssi.shimadzu.com/products/liquid-chromatography/knowledge-base/hplc-basics/uv-vs-pda-detectors.html

Further manual calculation of % RSD are suggested since two instruments are on defferent platform .

You can have a glimpse at these papers.

Adam B Shapiro The dextran is fluorescently labeled. Sorry if that was unclear.

I need to take the media out of the lab because I am analyzing the media itself after the experiment. We use a plate reader located in our normal lab space.

NaBH₄ can easily undergo solvolysis with protic solvents resulting in the generation of hydrogen and borates:

Therefore, a major point you need to be careful about is keeping everything cooled. An example in which this combination was used successfully can be found in the following work, maybe the process parameters from there can be partially transferred:

Hi

Maybe this way (CAS Number 1398-61-4)?

Best regards

Tomasz

Maria Monica Sianita Ali Nematollahzadeh I am unable to obtain the precipitation product of MIP polymerization using the same chemicals as mention above.

Yes there is bound to be disparity because one result will depend on the direct impact of rays emanating from the device in contact with the ores while the other result is affected by the level of dissolution of the ores, the reagents used and also the rays from the testing machine.

If you want to solve your problem as it appears in the image, I recommend using an equation of state for the enthalpy departure.

I also recommend the following articles:

-A computationally effective formulation of the thermodynamic properties of LiBr-H2O solutions from 273 to 500 K over full composition range

- Exergy calculation of lithium bromide-water solution and its application in the exergetic evaluation of absorption refrigeration systems LiBr-H2O

-Thermodynamic Evaluation of LiCl-H2O and LiBr-H2O Absorption Refrigeration Systems Based on a Novel Model and Algorithm

-Mathematical Model of a Lithium-Bromide/Water Absorption Refrigeration System Equipped with an Adiabatic Absorber

Cenker Aktemur

Each software may be using a different reference state.

To check if this is the case or not you can use a simple trick.

Just try and calculate the enthalpy or entropy difference between two states from the two software, (the same two states). If everything other than the reference state is the same, this should give you the same answer.

Hello there.

There are many compounds that are not found in ASPEN databases, new ones are incorporated in each version, but many are still missing.

One option that you have is to be able to create pseudo components and add them to ASPEN.

I leave you some tutorial links.

Regards.

Sampath Suranjan Salins I am talking about aspen plus not ansys fluent.

Is this Ansys Fluent analysis? its multiphase flow problems. U need to model the packing first the define the desiccant and material. Then apply suitable boundary conditions to solve the problem.

Dear Cenker Aktemur I found a report on the use of potassium formate/water (see attached) in which some severe corrosion problems were observed. They are listed on p. 21 of this report:

This is a common issue everywhere. you can try this

and

not sure but people can also add melamine to fishmeal to artificially increase protein content.

Kangning, L. I. U. X. J. I. A. G., and WU Xiuquan WU Caimei. "A Study on Qualitative and Quantitative Detection of Melamine Adulterated in Fish Meal by Fourier Transform Near Infrared Spectroscopy [J]." Chinese Journal of Animal Nutrition 3 (2010).

You might want to detect melamine in fishmeal and also in aquacultured fish or even poultry

Brilliant!

Thank you Azeez A. Barzinjy and Atef F. Qasrawi

Coloque el agua de mar en un baño de maría con hielo para mantener el agua fría y agregue lentamente NaOH hasta que alcance el PH 12.

Dear Dr. Keith White ,

I suggest you to have a look at the following, interesting papers:

-Non-stoichiometric oxide and metal interfaces and reactions

R.A. Bennett, J.S. Mulley, M. Basham,·M. Nolan,·S.D. Elliott,·P.A. Mulheran

Appl Phys A, 96: 543–548 (2009)

Available on RG at: https://www.researchgate.net/publication/226332421_Non-stoichiometric_oxide_and_metal_interfaces_and_reactions

-Non-equilibrium Oxidation States of Zirconium during Early Stages of Metal Oxidation

Wen Ma, F. William Herbert, Sanjaya D. Senanayake and Bilge Yildiz

Papers: BNL-111675-2015-JA

Available at: https://www.bnl.gov/isd/documents/92582.pdf

-Study of SiO2/Si Interface by Surface Techniques

Rodica Ghita, Constantin Logofatu, Catalin-Constantin Negrila, Florica Ungureanu, Costel Cotirlan, Adrian-Stefan Manea, Mihail-Florin Lazarescu and Corneliu Ghica

Chapter of book: Crystalline Silicon - Properties and Uses (2011)

Available at: https://www.intechopen.com/books/crystalline-silicon-properties-and-uses/study-of-sio2-si-interface-by-surface-techniques

-New insight on early oxidation stages of austenitic stainless steelfromin situXPS analysis on single-crystalline Fe-18Cr-13Ni

Li Ma, Frederic Wiame, Vincent Maurice, Philippe Marcus

Corrosion Science, Elsevier, 140, pp.205-216 (2018)

Available at: https://hal.archives-ouvertes.fr/hal-02349690/document

-Direct observation of pure pentavalent uranium in U2O5thin films by high resolution photoemission spectroscopy

T. Gouder, R. Eloirdi & R. Caciuffo

ScientificREPORTS, 8:8306 (2018)

Available at: https://www.nature.com/articles/s41598-018-26594-z.pdf?origin=ppub

Best regards, Pierluigi Traverso.

it might be air bubble filled your bottle before sample and after sample also

just check the error.

Dear Cory Camasta, Three degrees of freedom come from free motion, one from rotational and one from vibrational & E= 5/2 K_BT. The remaining rotational degree has a very small moment of inertia as some participants noted previously.

See the following external post for the full explanation regarding the separation of levels mentioned by Prof. :

https://physics.stackexchange.com/questions/168943/in-counting-degrees-of-freedom-of-a-linear-molecule-why-is-rotation-about-the-a

Thank you for your response.

Dear Kenkar,

In diffusion absorption coolers regarding to the heat performance of the system, ammonia/water couple with alumina (Al2O3) particles in nano-size can be a better option. It can provide better absorption of heat from the generator and faster evaporation of the cooler from the cooling/absorption fluid. Considering the effect of fluids containing nanoparticles the connection units of the heat transfer in the system operation time of the system might be reduced due to shorter heat transfer periods.

Ashish

Dear Nicholas,

That is true., By taking care of R41 which is flammable , performance value can be increased.

Ashish

from above link you can know recent methods to determine H2O2

Hi,

You may make an inquiry at Alfa Chemistry, they offer kinds of chemicals for research use.

Thank you dear colleague.

Dear Yasir Iqbal,

One of my favourite book is the encyclopedia of spectroscopy and spectrometry (John C. Lindon, George E. Tranter, David. W. Koppenaal ; Eds), 2010. I would also recommend some other books specialized in NMR and fluorescence.

interesting question

Dear Jayant,

There is no information about Ni content, but at first sight it fits S32101-lean duplex steel. This steel grade contains from 1.35 to 1.7%. Ni. The two-phase structure is magnetic.

Compare e.g. with: Niagaj, J. (2012). Ferrite content measurements in S32101 lean duplex stainless steel and welded joints. Archives of Metallurgy and Materials, 57(3), 779-787.

Maybe someone has a different idea?

Best regards,

Dariusz

Mohamed-Mourad Lafifi Thanks a lot for helping me & taking forward to my research!

A biosensor generally consists of at least two functional components: a molecular recognition element (receptor) that selectively interacts with its target analyte (e.g., ions, DNA, antibodies, cells, and microorganisms) and a physicochemical transducer. The latter converts the bio-recognition information into a measurable quantity, being an electrochemical, electrical, optical, magnetic, mass-sensitive, or thermal signal.

Due to the fact that biological analytes are often hard to detect purely on basis of their intrinsic physical properties, biosensors often require labels such as enzymes and fluorescent or radioactive molecules attached to the targeted analyte. As a result, the final sensor signal corresponds to the amount of labels, representing the number of bound target molecules. As a drawback, label-based technologies are often labor- and cost-intensive as well as time-consuming. In addition, labeling of biomolecules can block active binding sites and alter the binding properties. Altogether, this may adversely affect the affinity-based interaction between the recognition elements and the target molecules.

In contrast, label-free biosensing technologies, by definition, do not require the use of labels to facilitate measurements. Instead, they utilize intrinsic physical properties of the analytes, such as molecular weight, size, charge, electrical impedance, dielectric permittivity, or refractive index, to detect their presence in a sample. Label-free biosensing methods have made enormous progress in recent years due to their ability for rapid and inexpensive bio-detection in small reaction volumes. Moreover, they lend themselves for integration into lab-on-chip platforms and allow monitoring the concentration of target analytes in real time.

See also recently published book: M.J. Schöning, A. Poghossian, Label-free biosensing: Advanced Materials, Devices and Applications, Elsevier, 2018.

Please look at the following below link and the attahed book which may help you in your analysis:

Thanks

hey, sometimes the sulfate in the medium can precipitate with metals (like Mn), in my medium it was sulfate ions the problem, when I removed them no more Mn precipitates...

You may follow the method of Burdige et al. (1992) or Sharp et al. (2002).

Please look at the following below links which may help you in your analysis:

http://www.botanicalauthentication.org/index.php/Euphrasia_stricta_(aerial_parts) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115993/pdf/bmj-31-1-29.pdf

Thanks

Practically it is very difficult to remove carbon from steel by just remelting. Carbon can be removed by introducing oxygen in steel (by blowing, or by addition of oxygen bearing agents like scrap, iron ore, mill scale etc.)

Even by doing so, first elements which has got higher affinity to oxygen will react first like (Al, Si etc), and your whole chemistry will be disturbed.