Analytical Chemistry Techniques - Science method

TGA can measure the amount of materials lost during heating. However, it can not determine what are the materials. To confirm the content of the released gas, TGA-MS should be used.

Dear Esteemed Colleague,

Greetings. I trust this message finds you well and thriving in your scientific pursuits, particularly in the area of surface chemistry and characterization. Your inquiry about the mathematical formula for calculating functional groups on surfaces such as carbon materials via Boehm titration is both important and insightful. The Boehm titration technique is a cornerstone in the quantitative analysis of acidic and basic surface functional groups, providing invaluable data for material scientists and chemists alike. Below, I provide a detailed exposition on the formulation and methodology for calculating the concentration of these functional groups using Boehm titration.

Overview of Boehm Titration

Boehm titration is a technique designed to quantify the acidic and basic functional groups present on the surface of carbonaceous materials. This method involves treating the sample with a series of bases and acids to neutralize acidic and basic sites, respectively. The quantity of acid or base that reacts with the sample surface groups is then measured, providing an estimate of the functional group content.

Mathematical Formulation

To calculate the concentration of surface functional groups, the following formula is commonly employed:

�=(�blank−�sample)×��C=m(Vblank​−Vsample​)×N​

where:

Step-by-Step Calculation

Considerations and Best Practices

By adhering to these guidelines and employing the formula with diligence, you can accurately quantify the functional groups present on the surface of carbon materials via Boehm titration. This quantification is essential for understanding the chemical behavior and potential applications of these materials.

Should you require further clarification or wish to explore more about the application of Boehm titration in material science, please do not hesitate to reach out. Your dedication to advancing our understanding of material surfaces is commendable, and I am here to support your research endeavors.

Warm regards.

Check out this protocol list; it might provide additional insights for resolving the issue.

Tripti Mishra,

ESI-Ms is a very sensitive technique and the least unimaginable soluble amount will be detected.

Back to your original question (and I am done with this thread)... You observed a small (tiny) difference in Rt from small changes you made to the mobile phase composition. No worries, this is normal because no two columns are the same and each may interact to a different degree (or none at all) when you make small changes to the mobile phase composition. Try 20 different C18 columns and you may find some show no change at all, some do. Pick and choose the one that you want for the application (this is what we do in analytical laboratories). The reason for the observed change (change, not "drift") is due to multiple interactions of the solute on the surface of the support. Hard to say if it is electronic or ionization in nature, but it is so small, practically, it does not matter. All chromatographers are familiar with this (no need to 'explain it'). Run enough samples and you will see it. In fact, the one thing that they might question is why you would use a mobile phase of just ammonium formate without an acid (e.g.formic). Why not use a buffer? For LC-MS applications, most would benefit from such a solution to promote ionization and maybe change the separation factor too (depends on samples).

The ferrous chloride salt (possibly hydrated) can be generally expected to be partially oxidized, at least to trace level. When (freshly) dissolved in aq. dil. HCl, you may consider to reduce contaminant ferric ions to the ferrous state by adding electrolytic iron powder (a few wt% of the weighted salt). Then the sol. should be heated (not boiled) to facilitate ferric to ferrous reduction and the dissolution of any possibly excess of ferrous chloride; cooled to room temperature; being then either vacuum filtered while using nitrogen as blanketing gas, or pressure filtered by using nitrogen as pressurizing gas. Hydrogen can possibly be released during the purification process, owing to the concomitant reaction of metallic iron with HCl: Fe + 2HCl → FeCl₂ + H₂. Water should be either distilled or both deionized and N₂-purged or boiled. The purified ferrous chloride / HCl aq. solution may then be redox-titrated, if required.

because free radical changes,have occurred when activating,or exposted to uv radiation

If your funnel was stuck to the flask neck it was most probably due to water finding its way in between the funnel and the flask neck either before or during the filtration. You should stop vacuuming the pump as soon as you see it otherwise it'll get even more stuck. If it is slightly stuck, try putting a towel wet with hot water over the connection for some time. If this doesn't loosen it, you can try flowing hot water over the connection to evaporate the moisture inside. As another solution, you can try sonicating (if that's physically possible) the glassware.

Mind that you need to be really careful handling the glassware as they are usually really fragile. So try less extreme stuff first.

It can dissolve easily with ammonium bicarbonate, or ammonia and carbon dioxide, in such way calcium sulfate converted to calcium carbonate and ammonium sulfate, the calcium carbonate then precipitated and ammonium sulfate can be used as fertilizer. the only problem which needs to overcome is coating of calcium carbonate over calcium sulfate particles, hence, the good mixing is necessary to prevent such coating,

@Shaina Mercy Fernandes

I think there must be some problem with your solvent (water/aqueous buffer in this case). Check the fluorescence of blank solvent. To avoid such interference, always use triple distilled water.

Thanks Matthias Knarr

Very promising

The polymerase does not know that. The thing is that, in the first step, the polymerase will copy everything (into a complementary strand) from the primers. In the second step, this complementary strands now will have attached the another primer, so it delimits the region to be copied. Let's put an example focusing only on one strand: the direct primer will allow the polymerase to start the amplification from an end. After this step, you will have already delimited one part of your amplicon. In the second step, as the strand is the complementary one now, the primer bound will be the reverse, so delimitating the another end of your amplicon.

I don't know if I was able to explain myself as it is difficult to explain by words, but I hope it helped you

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.

I use HPLC method to check the monosaccharide content.

Dear Daniyal Ahmed just in case that this question is still of interest to you: The article cited below contains a detailed description of how to make oleum in the laboratory:

Personally I would suggest to buy oleum from commercial sources as it is an industrial product manufactured on a large scale.

Hello dear

I have the same problem like the one you explianed. Did you realize the problem? I can not produce gel with oxidized alginate and gelatin. Was the problem the type of the gelatin? Or the pH of the solutions should be specific?

Calcium Phosphate should not be effected by the persulfate. There would be no reaction of the persulfate with either the calcium or the phosphate. Calcium phosphote is insoluble; however, the solubility is pH dependent. If the solution is acidic below a pH of about 4 , the equilibrium will shitf towards the monobasic form of the phosphate which will result in the solubility of the calcium phosphate.

How we calculate total impurities based on LOQ and RF values

find info in above mentioned link

find the following link

Following

I think in simple terms we have a training issue here. Tao, basic GC method development requires a solid understanding of the fundamental chromatography principles and hardware/software used (instrument). Learning these fundamentals takes time (years) and is critical to using and developing proper GC methods that provide accurate data.

You report a 10% variation of some type which has you concerned (and you should be concerned, but do not say what this variation is or how you measured it. Then you comment as follows:

"For the same sample, if I inject it multiple times, I usually get below 1%RSD. It is the quantification that I think I'm having the most problem with." - - So where does the 10% variation come from ? Is it in peak area totals or peak height measurements? For one compound, a few, all of them? What happens if you inject the same std, 6-times, at 3 different concentrations (low, middle ad high ranges)? What is the %RSD?

You also commented that;

"Although my calibration curve says correlation is greater than 0.99 so it came pretty confusing to me." - - You can have variation in peak signal areas/heights because these are averaged before being used in a calibration curve. They are not related to linearity at all. Those types of fundamentals, regarding the basic GC technique, must first be learned to appreciate how all of these parameters contribute to the reported results / data.

Web forums are a very poor training tools when the basic fundamentals are not well understood. While many of the concepts and ideas can be learned from books and articles (which I strongly recommend), hands-on time with a more experienced chromatographer will speed up the learning process for you 100x. My recommendation is that you obtain help locally first. Take some classes (esp. GC manufacturer operation classes), read some of the classic books on the topic, get more hands-on time to run your own experiments to 'see' cause vs effect with the system using standards. Troubleshooting to find a specific actual cause requires being there in-person (assume nothing) to provide high quality assistance, something that we can not do as well remotely.

There are chemical methods by which the chemical composition of the natural fibers can be determined. For example TAAPI procedure in which the individual components (alpha cellulose, hemicellulose and lignin) are separated and determined quantitatively. There are several research papers on the properties of natural fibers (such as Hildegardia populifolia uniaxial natural fabric, Tamarind Fruit fibers, Borassus fruit fibers, Ridge guard 3 dimensional fabrics etc) available in the literature which describe these procedures.

It's a late response, but I figured it now after struggling with the same challenge. How citing this book is dependent on the edition, assuming 2012 for now. It is generally accepted to cite this book as "APHA, 2012" in the text, although there are two more contributors/authors: AWWA, WEF. The editors are:

Rice, Eugene W.

Baird, a B.

Eaton, Andrew D.

Clesceri, Lenore S.

For the bibliography, it depends on which style you are using. These are other details you should input on Mendeley:

City: Washington, DC.

Edition: 22

Publisher: American Public Health Association

ISBN: 9780875530130

Hope you find it helpful :)

cAn anyone tell me procedure of nitric acid digestion in plants . i want full recepie step by step

Dissolve the acid in def add doc then add ammonium formate or acetate. Remove solvent work up. You get the corresponding abide. Good luck!

I do support Dr M.F.Wahab for fantastc discussions.

Isolation

- Principle

Nicotine is a classical alkaloid the separation of which teaches the

main principles of an alkaloid isolation. Consisting of a combination

of two tertiary amines of which the pyrrolidine is the stronger basic

one, nicotine is protonated in the plant and forms carboxylate salts such as formate, acetate or maleate. Therefore, the fi rst and typical step is to bring the alkaloid into a distinctively strong alkaline environment, such as NaOH solution to cleave the organic salts and release free nicotine into the aqueous solution. Nicotine is readily soluble in water due to its ability to act as an acceptor for hydrogen bonds to water.

Another useful property is its volatility with water vapour. This allows

steam distillation to be used for a very selective separation of nicotine

from many other water-soluble tobacco constituents. In the distillate,

the alkaloid is protonated by addition of hydrochloric acid and the

nicotinium ions formed are precipitated by addition of sodium picrate

solution. The yellow nicotinium picrate formed is pure. To obtain the

free alkaloid base, a second alkaline cleavage as with the starting tobacco is necessary with the nicotinium picrate. The free base is extracted from the basic solution with diethyl ether and fi nally purifi ed by a distillation in vacuo.

Hello, see the info below you can find some news there.

Good luck!

A large number of methods exist for porphyrin demetalation which vary in their execution. One of the latest methods uses ultrasound; see: Chengguo Sun, Bingcheng Hu, Weiyou Zhou, Shichao Xu and Zuliang Liu, Investigations on the demetalation of metalloporphyrins under ultrasound irradiation, Ultrasonics Sonochemistry, 10.1016/j.ultsonch.2010.08.010, 18, 2, (501-505), (2011).

Briefly, you need to reduce the iron (III) to iron (II) in the presence of a suitable acid. (ranging from HCl, formic acid to acetic acid). The change in ionic radius in the reduced form of iron makes it easier to expel from the porphyrin ring. Ensure that use either a suitable standard and TLC and 1H-NMR if you have access. The 1H-spectrum for the standard is found rather upfield at around -4.00 pm and should integrate to 2 ppm. Check downfield down to at least 100 ppm to ensure that the iron has been completely expelled. Various methods for demetallation are listed in the above reference. The first useful method was published by the Hans Fischer group and his groundbreaking work: https://www.wikiwand.com/en/Hans_Fischer

Standard PPIX/heminCl can be reliably purchased from Frontier Scientific. Although this post is too late to assist you, it may prove useful to others.

FMDI

Centre for Natural Product Discover, Liverpool.

Dear All,

I have a query regarding solubility of KOH in DMF. When we are trying to dissolve KOH in DMF, color of the solution turns black. What kind of reaction is taking place here?

Mohammed M. Obeid Thank you and good luck to you too for your future work

I sort of have a similar issue, though mine is with a reagent -- it's sensitive to light, and oxygen, so I want to minimize the reagent volume in each aliquot. When in use, I only use 0.5uL for each sample (usually no more than 20 samples), so there is a lot of reagent waste. I looked for a similarly small-volume insert or vial to minimize the interaction with oxygen upon being pierced. I found an insert from a supplier that *said* it held 50uL, but they were only counting the little bulb at the bottom, not the entire volume of the insert. So instead, I currently use a 100uL insert, filled only about 1/3 full, and the extra volume in the entire vial is filled with nitrogen. Your question made me think of the dimensions of 10uL volume. This is the result.

There is a problem with the math of the basic measurements -- I did a quick calculation using reference to 10ga, 20ga, and 30ga needles (I'm not sure the width of your autosampler needle) using Wikipedia as a source for width of these gauges. If the vial were to hold a maximum of 10uL, a 10ga needle could drop into the vial only 1.10mm deep (20ga: 15.4mm; 30ga: 131mm). Then the total volume of pickup at a maximum (unless drawing the sample while descending into the vial) would be 6.25uL (20ga: 4.41uL; 30ga: 2.61uL). At such a low volume, you would have to take into account the volume of the metal of the needle. Though it's a trade off: the finer the gauge of the needle, the softer it will become, and less able to pierce a vial septa.

The only other idea (if you want to be a bit creative) is to get short vials and lose them at the bottom of the autosampler well(s), but being short would hold a smaller volume. AND since it's at the bottom already, it would allow for the full extension of the needle.

Consider keeping the trays, covering/washing/marking the used wells, and use other spots on the tray for the new sample set.

Hope that helps give some perspective.

(sorry for the lengthy post and the 4-year delay)

Your calibration is statistical; you are fitting a curve to a series of calibration points. It has error associated with the curve. When you get down to a low enough concentration, and you have calibrated correctly, then you can, statistically, get negative numbers. This is normal; in fact, any decent auditor would applaud you for doing your job correctly. As long as you are not getting large negative numbers then the data is telling you that the element(s) you are measuring are not present at your detection limit. This is also why you determine, and use, a lower limit of detection (LOD) and a lower limit of quantification (LOQ). These indicate the point at which your calibration is no longer valid; you shouldn't report values below your LOD.

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Hi Jyoti Matolia

Ce and Qe are obtained by batch experiments not column studies. The formulas mentioned by Mr. Omar Khelifi are used in batch adsorption experiments. In fixed-bed studies, you dont have an equilibrim concentration, because the concentration varies by time and during the whole length of the bed. You may not reach to the equlibrium state because of having flowrate.

good luck

On the plant surface (and in solution), paraquat is rapidly broken down photochemically.

First you have to deal with a fundamental difficulty. Starch is a mixture of two biopolymers, linear amylose (MW ca 10E6) and branched amylopectin (MW ca 10E8). So starch has a bimodal molar mass distribution which is very broad. Because for most starches, amylopectin is the dominant fraction (typically 70-80 %) and because the preferred experimental method is size exclusion chromatography with light scattering detection, which is more sensitive to the high molar mass species, the molar mass of amylopectin is a rather good approximation for that of whole starch, except for the amylose-rich starches.

In doing molar mass determinations one has to ensure that the starch has been molecularly dissolved in a way that no molecular degradation has occurred. This is not a simple task. Fortunately, suitable methods have been developed and literature values for most common starches are available. The authors of the paper provided by Md. Abdur Rahman are real experts in the field but their paper does not provide numerical values. Data for various starches were presented in a paper by Yoo and Jane (Carbohydr. Polym. 49 (2002) 307-314) which you find in the attachment.

I think optimize your mobile phase and use suitable column (This observation is from the area u got, where proportionaly change in area respect to concentration).

C1 x V1= C2 x V2

C1 is the initial concentration(37%) C2 is the diluted concentration(5%)

for example if you want to prepare 100ml of 5% solution you do the following:

37 x V1= 5 x 100 => V1=13.51ml

So you must take 13.5 ml out of your initial solution (37%) and add them to a 100 ml volumetric flask then add distilled water until the bottom of the meniscus is level with the horizontal line on the neck of the flask.

Structure elucidation involves identification of various parts of structure like its functional groups, double/triple bonds, cyclic groups, molecular weight, etc.

We need to let students know that all the individual techniques have their own specific application.

But, with advancements in Mass and IR techniques they have become more helpful in structure elucidation. Moreover, NMR would be one of the top preference for any organic molecule as it gives almost a clear picture of the structure along with any impurities in the compound.

SO, I WOULD SUGGEST NMR.

Thanks @Mohammed Mohammed . Really appreciate it!

Miroslaw,

I think of fouling as a blockages that cause maldistribution. A burn will sometimes remove a blockage (e.g. if it is coke blocking a pore) but sometimes it will not and dumping and reloading catalyst is often necessary, especially if he blockage is caused by scale/metals instead of hydocarbons.

Coking/carbon disposition is the most common way for commercial Hydrotreating, Catalytic Cracking and Hydrocracking catalyst to lose actiity. Historically these catalyst were :regenerated" with a burn but recently the trend has been to dump catalyst and send it to an offsite regeneration facitity for screnning and coke burning. Arsenic and lead are posons that will permanently deactivate most catalyst and cause them to be unregenerable via burn.

I think of an inhibitor as a material that competes with reactant for catalyst sites inhibition is reversable. If the inhibitor is removed from the feed the rate of the desired reaction will increase. An inhibitor may also increase the rate of coking. If the calayst site is coked up it will usually require a burn(with air or O2) to remove the coke. that has closed up catalysyt pores and/or blocked active sites

.

Poisoning and coking are forms of catalyst deactivation that usually require a stoppage either for regeneration or catalyst replacement.You seem to disagree with the comment it can sometimesbe removed during a regeneration (usually a burn with air or O2). I agree it is not really a "poison" if you can remove it with air/ burn.

All catalyst can be "regenerated" if you take extreme enough measures.

For my purposes - in the refining indusrty- catalyst is not regenerable if activity can not be recovered with a simple burn or other relatively minor procedures like a wash with a solvent.

However even then the active metals can be reclamed and used to make new catalyst.

Does anyone know of a Acquity UPC2 users forum?

I just re-read the question and the answers. If the surface is darkened, this may be due to the formation of Pt-oxide, especially at temperatures below 1000°C. However, these oxides are rather volatile. The only thing to do is to put the crucible in a furnace and heat up to 1400°C in air. The oxides are volatile and will disappear and the crucible looks as new.

Thank you for answering.

What exactly do you mean with HILIC? For that mode, you need a polar stationary phase, and the pillar array format is only available in RP mode. Pharmafluidics only sells C18 end capped coated pillars. This is exactly why I started to wonder about the other separation modes. I understand that when the interpillar distance is too small, it would clog. However, if C18 modifications are possible (which is a very long chain, longer than others), then this made me think that other coatings should be possible as well... but somewhere here in the thinking process I must be making a mistake because I have not found any paper discussing this, or other modes with pillar array columns.

Follow this link

regards

1- First, a Beaker or a crucible should be brought, weighed (Assume that the weight is 100 g)

2- Transfer the extract to the Beaker

3- The solvent used in the extraction process shall be disposed of by evaporation of until the dry matter is obtained as far as possible

4- The beaker is weighed after full evaporation of the solvent (Assume that the weight is 110 gm)

5- The weight of the extract (the weight of the beaker with the extract - the weight of the empty beaker) = 110-100 = 10 g

6- The extract is dissolved in the appropriate solvent Ethyl alcohol is often used and an emulsifier may be added (the amount of the solvent is calculated to obtain the desired concentration(

1- The extract is dissolved in the minimum amount of suitable solvent and then a quantitative transfer is done to a volumetric flask with a final size of 100 ml (the appropriate size for the quantity of the extract).

10gm/100ml = 10×103mg/100ml= 100 mg/ml

Different concentrations could be prepared from that stock solution

V1×C1 (before dilution) = V2×C2 (after dilution)( the concentration which we would to prepare )

? ×100 = 5×100

V1= 5×100/100= 5 ml

Take 5 ml of stock solution (Conc 100mg/ ml) and supplement with appropriate solvent to 100 ml in volumetric flask.

? ×100 = 5×100

V1= 0.5×100/100= 0.5 ml

Take 0.5 ml of stock solution (Conc 100mg/ ml) and supplement with appropriate solvent to 100 ml in volumetric flask.

In that case we use a DMSO 0.5% instead of the solvent

How did you prepare the reaction buffer?

Simple: The CO₂ content of the air is different. If the CO₂ content decreases after the background measurement, the corresponding peaks are negative in the absorbance spectrum otherwise if the content increases you get the usual positive peaks.

Dear Ali,

there were several papers in which detection of peroxydisulfate and peroxymonosulfate was achieved by ion chromatography and HPLC, probably by this you could distinguish between h. peroxide and PS.

Please see:

Moreover, one chapter in this review is devoted to the determination methods of PS:

Regards,

Stan

N-Methyl-2-pyrrolidone is a regulated substance. Attached is the OSHA method which uses a DB-Wax column in a GC-FID.

I suspect you have not built in the sampling codes at the initiation stage.

Soumitra K. Mallick

for Soumitra K. Mallick, Nick Hamburger, Sandipan Mallick

vario TOC select - TOC/TNb analysis without limitations

I have tested this method for methanol production from PEC reduction of CO2. provided the quantity of of the methanol is high enough to an extent it is measurable by this method, then its good to follow. But from my experience, methanol produced from CO2 reduction was not detectable by this method..but GC does.

Dear Professor Isam,

I know that Hydrogen with Oxygen interaction to generate water requires a strong power "energy". I just thought this power can be generated from induction coil energy. I thought this idea may be applicable to implement

Thank you very much

Best wishes,

Osman

CQA (certified quality auditor)

CQE (certified quality engineer)

Dear Sir. Concerning your issue about the best resources/databases/websites for analytical chemistry. Analytical techniques providing more information, in particular molecular spectrometry, are preferred for identification. Other techniques are just briefly considered, with for the exception of chromatography, whose combination with spectrometric techniques sharply increases possibilities and trueness of identification. As a whole, mass spectrometry is superior to other spectral techniques in such features as sensitivity, selectivity, generation possibility of molecular mass/ formula, and combinability with chromatography. Different types of mass spectrometric instruments are outlined, with many performances tabulated. Experimental conditions for identification of volatile, non-volatile, and high-molecule compounds are discussed. Next, classification of chemical methodologies is given where screening and confirmatory methods are noted. Related procedures, sample treatment, and quantitative determination are also considered as ones affecting qualitative analysis. I think the following below links and the attached file may help you in your analysis:

https://en.wikibooks.org/wiki/Chemical_Information_Sources/Analytical_Chemistry_Searches

https://www.hindawi.com/journals/isrn/2012/801607/

https://www.ncbi.nlm.nih.gov/books/NBK218064/pdf/Bookshelf_NBK218064.pdf

Thanks

Dear Sir. Concerning your issue about how to check the biocompatibility of a polymeric material. An in vivo method is described for screening polymeric materials for biocompatibility. The test is based on grading acute and subacute tissue reactions at 7 and 28 days, respectively, following implantation in rats. The method is reproducible and reliable. It is designed to provide uniform test criteria for biocompatibility assessment in the early phases of the development of surgical implant materials. I think the following below links may help you in your analysis:

http://onlinelibrary.wiley.com/doi/10.1002/jbm.820120207/abstract

http://www.pharmacopeia.cn/v29240/usp29nf24s0_c1031.html https://www.fda.gov/downloads/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm348890.pdf

Thanks

Dear Mr. Hodaei,

Your question is interesting in the way you try to understand the behaviour of your material in solution, which can be of potential value in applications such as adsorption. However, your writing mentions Fe²⁺ and Fe³⁺ as charge of iron, while the oxidation states II+ and III+ were mentioned, respectively. The apparently small difference has strong consequences to the overall speciation. No iron in such constellation is assumed free and ionic, but bond to oxygen. At the outer surface of Fe_xO_y nanoparticles, oxide or hydroxide groups will determine governing charge and interaction towards species. Avoid "complexation" as choice of interaction unitl you actually characterized that interaction mechanism . It is not likely Fe_xO_y have the potential to chelate certain compounds in solution.

Regarding the available analytical instrumentation, consider solid phase characterization, for instance using TEM-EDX, EELS, Mössbauer spectroscopy or XRD. The reference applies some of these techniques for the characterization of Fe₃O₄ nanopartikels in a porous host.

Best regards, Karel Folens

1 M (460 mg) of PbI₂ is fully soluble in 1 ml DMF at 70⁰C  for over night stirring. PbI₂ in DMF is transparent yellowish solution at 70C but at room temperature it,s converted into gel like appearance but after heating it again converted into transparent solution. I have prepared this solution many times for the 2 step perovskite coating. In your case I think there is problem with PbI₂ purity. I am using PbI₂ of sigma (98% Purity). 

I do not see how the paper you reference is related?

Mel: A guard column is a generic term to describe any "column" which is placed in front of the actual method (analysis) column to protect it. We characterize columns, not 'guard columns' so I am unaware of any articles designed to compare or describe them. Normally, a guard column only contains a filter or a tiny amount of stationary phase and the goal is to make them invisible (you may introduce more error by adding them). They add delay volume and can result in band spreading (undesirable). Regarding efficiency, you asked "how low it can be"? That question can not be answered as guard columns are not used for (and should not be used for) separation, so 'efficiency' is not used. This is a small filter we are talking about. 

To generalize, Guard Column dimensions should be very small as we do not want them to negatively contribute or impact the chromatography method being used at all. They principally serve as an expensive filter or solvent saturation device (esp in NP) only. Normally, they contain the same packing material as the working column (so as to NOT change or interfere with the actual method). They are NOT replacements for an actual HPLC column at all. We do not normally use them in method development. "Efficiency" is not relevant and measuring it also is not relevant. Those metrics are reserved for actual columns used in the analysis, not a pre-filter such as a guard column. Guard columns are normally described by their packing material details (support type, functionality and particle size).

Why are you interested in these accessories? We do not use them for analysis.

Most HPLC's come equipped with a UV detector (PDA/DAD).  An IR detector is known but not typically used since everything absorbs (thus molecular spectroscopy) including mobile phase solvents like Methanol, Water....

Dear Anindita.

Kindly share literature method as i am also struggling for Estimation in Cream 

After following the suggestions of my RG colleagues, a sign that you are on the right track is that the pH you will find out will be above 7 because:

HCOOH & NaOH are completely soluble in water & they will undergo a neutralization reaction: HCOOH + NaOH → HCOONa + H₂O .

The product is an aqueous solution of sodium methanoate "which is a basic salt".The use of a pH meter for this solution will confirm that the pH is > 7.

Optimizing the gc-part (separation) without the trap is a good advice. You can introduce the trap later if you are not satisfied with the sensitivity. With the trap you'll gain a factor 20 to 100 ,depending on the analyte and settings, and it si not that hard to master. The main problem, in my opinion, is finding a suitable internal standard. For the selection of the trap there is plenty of information online about the properties of available absorbents although your manufacturer may offer a limited choice (PE has only two traps). Filling your own traps is an interesting option.

In your case , if you'll need the trap, I would go for a low equilibration temperature and a trap that is not retaining water and avoid excessive dry purging.

Typically you get that kind of noise out of a UV detector when you either have a saturated reference channel or you have bubble formation. Not familiar with your system, so I have no idea as to how you are mixing the ACN and H2O (low pressure, high pressure, etc), and therefore I have no idea if you could have bubble formation. 

I question the need for a 100 minute separation for something that is relatively simple. Your gradient certainly can be significantly faster. I also question the choice of ACN. You know for certain that the phenols are highly soluble in alcohol; why not use methanol rather than ACN for the separation? 

Have you checked the pka of the compounds? Are you certain that acetic acid is your best choice? I would have probably leaned more towards formic acid or TFA for this analysis.

Dear V mani Rathnam

(1) You need to read a simple text on the fundamentals of quantitation in gas chromatography.

(2)Your faculty advisor should have given you this fundamental guidance before allowing you to use the instrument.

(3)None of these instruments is an 'answer machine'. The best technique for quantitation depends on the conditions, sample and hardware.

**** I personally do not trust any commercial software to do the job right, so I export all raw signal data into Excel worksheets and do my own analysis of the data. I strongly recommend that students and professionals alike do this until there is proof that the instrument and software are truthful.

XRD will provide information about the phase composition. You can use XRF in order to get the detailed chemical composition. Also, the use of SEM attached with EDS will provide information on elemental composition.

Thank you for this question because it aroused my curiosity in the search for the subject and knew the beautiful information about the subject

  Please, press on the following website link for more information

Thank you for your answer and sorry for the late response. We just started with the project and we try to chractarize real samples as thoroughly as possible. However, you were already pointing to the key fact: The elution of particle sorbed POPs and their recoveries. We will perform some validation work with real samples concerning the elution..... 

Dear Ahmed,

Thank you very much for the article. Your help is much appreciated.

Kind Regards,

Sony

 CPME (supposedly Cyclopentyl methyl ether) is not a Bronsted acid, so the simplest method is titration of acetic acid in the mixture by a base. The mixture may be diluted in water or in MeOH/H2O or EtOH/H2O if CPME is not soluble enough. A pH-meter or an acid-base indicator may be used for determining the equivalence.

1) Weight difference using analytical weights after storage them on the dry compounds (i.e. P₂O₅, etc)

2) Absorbed water can work as medium for organic compounds hydrolysis

It looks like your peaks have comparable responses, but the baseline is all over the place.  Is this a UV detector?  If so, what wavelength are you using and what is the mobile phase solvent system?  It looks like one of the chromatograms has a stable baseline whereas the others show some drift.  My initial thought would be that this is either lack of equilibration, or a loss of equilibrium during the analysis.  This looks like more of an instrument/method issue rather than a sample effect.

Since Cyclopentyl methyl ether (CPME) is an ethereal solvent, will DB-FFAP (agilent) work for it ?

Agreements with  Peter Apps

Paul Milham the material is technical grade insecticide.