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Questions tagged [chromatography]

collective term for a set of laboratory techniques for the separation of mixtures

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0answers
37 views

ApexTrack: peak tail looks like a shoulder

I'm trying to implement ApexTrack algorithm in my software by following the description written by Waters. But many chromatograms that I see have noticeable tailing of peaks: . No matter what ...
7
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1answer
523 views

What is the purpose of trimming the bottom corners of TLC plates?

During my chemistry lab course, I was told by my instructor to make 2 small cuts on the bottom corners of the TLC (Thin-Layer Chromatography) plate. Does this make the solvent rise uniformly on the ...
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2answers
29 views

In Ion Chromatography instrument, Does the specific conductivity (peak area) of an analyte depends upon background conductivity?

In Ion Chromatography instrument, Does the specific conductivity (peak area) of an analyte depends upon background conductivity ? Assume Specific Conductivity (peak area) of fluoride ion is 4 unit ...
-3
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2answers
175 views

Pre-Hydrogen Feature On the Output Of a Gas Chromatography Thermal Conductivity Detector

A candidate for "dark matter", predicted and now apparently detected to have both a higher thermal conductivity and higher diffusion rate than H2 is purported in this PowerPoint Presentation file. ...
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0answers
26 views

Monitoring amino acid esterification

I am trying to monitor the esterification of a non UV active amino acid.I used thionyl chloride and Methanol as reagents. As amino group is unprotected, Ninhydrin should give positive result for both ...
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0answers
30 views

Impediments to GC-MS characterization of petroleum products

In an attempt to characterize, and sometimes to 'match' oil on feathers of birds, a laboratory utilize gas chromatographic - mass spectrometry. Persons likely to encounter oiled birds are advise to ...
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1answer
25 views

Separation of sugar and fat in a column chromatography [closed]

I am chemist at organic and bioorganic chemistry,I want to know if we are separating sugar and fat in a column chromatography who will be down first ? and why ? Thank you.
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1answer
32 views

How can I use a solvent gradient in column chromatography? [closed]

I am working to use the column, there are a lot of videos which explain it, but I don't understand this statement in the procedure. The residue was finally purified by column chromatography using ...
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0answers
16 views

how could I make a file conversion from .spc (thermo fisher) in .cdf (Shimadzu) format file?

how could I make a file conversion from .spc (thermo fisher) in .cdf (Shimadzu) format file?
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1answer
110 views

What does it mean to equilibrate a column in size exclusion chromatography and why is a buffer used?

I'm reading a procedure on size exclusion chromatography and it says that the first step is to equilibrate the column with buffer. What does this mean?
2
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0answers
91 views

Pressure in Skoog Instrumental Analysis Problem 27-22b (gas chromatography)

Problem 27-22b in: Skoog; Holler; Crouch. Principles of Instrumental Analysis. Thomson Brooks/Cole (publisher varies by country) asks for corrected retention volumes. A compressibility factor, $j$ ...
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1answer
65 views

Can I get feedback on assignment? (chromatography)

HW question asks me why samples can be separated into their components by chromatography. My answer is that each component in the mixture will have different affinity for the solvent (mobile) phase as ...
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0answers
48 views

Can you convert smells to variables? [closed]

Is there a way to map smells to numerical values of different variables? I.e. With RGB colours, each colour is made up of numerical values from 0-255. For example, red is (255,0,0), and yellow is (...
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0answers
39 views

How to divide the peaks of two anion ions using ion chromatography?

I used an ion chromatography system (Dionex IC-2000) to determine the inorganic ions and acid from the samples collected in the atmosphere. For measuring $\ce{SO4^2-, NO3, Cl-}$, and low molecular ...
2
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0answers
51 views

Visualization of TLC plates

I'd like to know what exactly happens when various agents are used after developing a TLC plate, during the visualization phase, of sugars with anisaldehyde for example. I know that those compounds ...
1
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1answer
54 views

Sephadex and purification of products [closed]

Sephadex is useful for the separation and purification of many natural products. Is it also useful for the separation and purification of artificial chemicals (in organic synthesis ) or not and why ?
3
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1answer
56 views

Is the pressure in an HPLC system the same throughout?

I'm not sure if I'm articulating myself well enough, but here's my problem: I have a current HPLC system, where we typically have backpressure readouts of around 15 MPa. We are looking to get a new ...
3
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1answer
548 views

Why is Rf called Retardation Factor?

I understand that $$R_\mathrm{f} = \frac{\text{distance traveled by center of analyte spot } (b)}{\text{ distance travelled by solvent front } (a)}$$ What I do not understand is why this is called ...
0
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1answer
56 views

marijuana testing process [closed]

Does anyone know a bit about how costly and accurate are the current THC measurement techniques? Please speculate what drives cost chemicals, consumables or instrument time.
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1answer
18 views

What is the relation between the speed of various components of a mixture, and their respective Retardation Factors in adsorption chromatography? [closed]

Consider two components, I and II, of a mixture which is subject to adsorption column chromatography. Let I have higher adsorption than II. I know that Retardation Factor ($R_f$) of component II will ...
0
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1answer
159 views

Could thin layer chromatography separate enantiomers? [duplicate]

My textbook states the thin layer chromatography could separate enantiomers only if both/or the mobile and solid phases are chiral? Why so?
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0answers
347 views

Why is methamphetamine less polar then amphetamine? [closed]

The question is as stated in the title. Is there a general way to determine relative polarity of organic compounds? This question is for use in the context of the manner in which polarity of the ...
4
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1answer
48 views

What happens to the “leftover” Ions in the Mass Analyzer

I am very intrigued by what happens to the ions which do not make it to the detector in mass spectrometers, do they just pile up? I have never seen anyone clean our quadrupole, is this done? or do ...
3
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2answers
125 views

Is it possible to calculate the concentration percentage using chromatography paper?

I'm trying to calculate the concentrations of specific compounds using paper chromatography. Would I be able to calculate a rough estimate by comparing the size of each concentrated spot? If not is ...
4
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1answer
363 views

HPLC method for salicylic acid

Salicylic acid is a relatively polar compound hence I thought that normal phase would be preferred as the stationary phase of normal phase is polar. However, it is said that reverse phase would be the ...
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0answers
105 views

can you separate inorganic ions with chromatography?

For example, if you run a solution of sodium and potassium chloride through a colum? I am just wondering if i can get pure potassium chloride from a mixture of sodium and potassium chloride.
2
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0answers
223 views

Difference between batch and column mode?

I have heard Ion-exchange chromatography can be used in batch or column mode, have you got any idea how are those modes? I have looked descriptions all over books and web (Skoog for example, both ...
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1answer
39 views

Can I use chromatography to compare the amounts of chlorophyll in different leaves?

I have been unable to find a clear answer online about the effect that concentration of a solute has on the retention factor. If it is as I suspect, I should see plants with more chlorophyll having ...
1
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1answer
101 views

Can I use a 1:1 mixture of isopentyl alcohol and water as mobile phase to carry out paper chromatography of a mixture of red and blue ink?

Can I use a 1:1 mixture of isopentyl alcohol and water as mobile phase to carry out paper chromatography of a mixture of red and blue ink? We generally use ethanol water mixture as mobile phase for ...
2
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0answers
279 views

Predict polarity (TLC, column) using ChemSketch (-Draw)

I'm currently working on a project where I have to make and isolate often quite similar molecules. But, as I change the functional groups the overall electronic situation and polarity of the product ...
2
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0answers
131 views

Process Chromatography vs Solid Phase Extraction techniques

Process Chromatography is typically performed by flowing eluent from the top to the bottom of the column. The standard method of solid phase extraction at industrial scale e.g. to extract natural ...
9
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2answers
416 views

How to separate two diastereomeric amines?

I am developing a method to synthesize amines using organometallic catalysts and my reaction yield these two diastereomeric amines ($\ce{R2N}$ is, in this case, a morpholine group). With both being ...
0
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1answer
286 views

Affinity to mobile or stationary phase during column chromatography [closed]

I have carried a column chromatography and obtained two compounds. The first one is liquid (ester) and the second one is solid (nitro) yet I know that the second compound is less polar than the first ...
5
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2answers
12k views

Normal phase vs reverse phase HPLC

What is the difference between normal phase and reverse phase high-performance liquid chromatography?
3
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0answers
396 views

Purification of polar NHS esters

What are the options that I might be missing for the purification of a molecule with the following characteristic: Contains an activated ester that reacts with water (NHS) Reacts readily with ...
3
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1answer
348 views

Diffusion/Streaky bands on TLC plate

These days I am working on a research project where I am supposed to run TLC for samples which are wax extracts from coconut butten nuts using chloroform as the solvent. All the samples have been ...
2
votes
1answer
86 views

Compare concentrations using LC/MS

Suppose I run a reaction and then pass the results through LC/MS to find the conversion. One idea could be to compare the peaks of the reactants to the peak of the product. But: MS peak will depend ...
3
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0answers
51 views

Dibenzoyl-L-tartaric acid won't show up on HPLC chromatogram

I'm trying to develop a method for HPLC to detect dibenzoyl-L-tartaric acid. Concentration doesn't matter at this point; I'm only concerned with detection. The problem I'm having is the compound won't ...
4
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1answer
67 views

Could chromatography induce a conformational change?

We'd been studying chromatography in our instrumental analysis course and I was wondering if chromatography could induce a conformational change. For example, you have a straight chain with a ...
1
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1answer
200 views

If I mix an aqueous solution of hydrogen chloride with an organic solvent, will the organic solvent contain hydrogen ions?

For example, let's say I mix $36\ \text{cm}^3$ 2-propanol, $9\ \text{cm}^3$ methyl ethyl ketone and $15\ \text{cm}^3$ hydrochloric acid with a concentration of $1,0\ \text{mol}/\text{dm}^3$. The ...
4
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0answers
89 views

How to make a sephadex slurry

I want to purify crude alpha-amylase with column chromatography. I am using a spehadex 75, But for some reason I can't find any information on how to make the slurry. I can quickly find tons of ...
1
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1answer
560 views

How to prepare and store anisaldehyde tlc staining solution? What will be the color of this solution? What is its shelf life?

I prepared anisaldehyde charring solution, and refrigerated it. Its color was yellow. However when I am using it for staining tlc plate, it is giving dark pink color on tlc plate surface and ...
0
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1answer
105 views

How well can triglycerides be resolved using TLC?

The only part of triglycerides that significantly interacts with a TLC plate are the ester moieties which are present in all triglycerides. Other than that, they do not differ much, except in mass (...
0
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1answer
184 views

In which pH range are silica-based TLC plates stable?

I am trying to understand why the experiment asks for raising the pH of a fairly acidic solution. The analytes should not be affected by it, so I thought the silica plate might be. Are silica-plates ...
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1answer
1k views

Is paper or water the stationary phase in paper chromatography?

I've been looking at about 10-ish sources, and half of them say that paper is the stationary phase, and the other half say that water is the stationary phase. I understand that water is on the paper ...
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0answers
141 views

Quantitative information from silica gel TLC plate?

I have a general question about thin-layer chromatography using silica gel. Can we get quantitative information from a TLC analysis? Is this mainly just the Rf or can we tell more? I'm guessing ...
3
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1answer
11k views

How to determine the order of elution in silica gel column chromatography?

Benzofuranoids ustusoranes A (1), B (2), and E (3) were isolated from Aspergillus ustus 094102. If these compounds were separated by column chromatography on silica gel, what would be the elution ...
0
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1answer
14k views

Do polar compounds travel further or less far than unpolar ones in hexane/ethyl acetate TLCs?

Would ethyl acetate/hexane be considered nonpolar or polar overall? I know that the ethyl acetate is polar and the hexane is nonpolar. I am trying to understand what if polar or nonpolar analgesics ...
4
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1answer
922 views

Normal Phase TLC using ethyl acetate as eluent

Compounds 1-3 were analyzed by normal phase TLC (shown) using ethyl acetate as the eluent. Assign spots on the TLC plate to compounds 1-3. 1: 2-acetoxybenzoic acid 2: 2-hydroxybenzoic acid 3: ...
4
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1answer
309 views

What inference can be made from the fact that there is no reversal in how three components eluate?

I gave an answer this question about TLC. I now realize that I am blundering my way through this question. The problem statement doesn't specify if the compounds to be eluted are polar or non-polar. ...