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Questions tagged [chromatography]

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

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Two peaks of one pure compound in GCMS?

Analyzed compound: imidacloprid Conditions: Column DB-5 30/0.32/0.25 Oven temperature: 30 or 60 (depends on DCM or ACN solvent respectively) - 300 (with 90 sec and 5 min holding time respectively) ...
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7 votes
1 answer
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Why are amber bottles used to store Water for HPLC?

Image Source: https://www.calpaclab.com/water-hplc-spectro-grade-4-liter-bottles-case-4/ted-ws2211-001 When ordering HPLC/Spectro grade Water for HPLC from certain vendors(not all), it comes in an ...
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Meaning for chromatography terms linear velocity and volume flow rate

I am learning about chromatography and there are two terms that confuse me a lot: linear velocity and volume flow rate. These terms are defined in Daniel Harris's Qualitative Chemical Analysis: ...
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What could lead to exaggerated positive LC-MS/MS test for tetrahydrocannabinol?

I was driving with the car and was involved in a minor traffic violation and I was submitted to a drug saliva test. The sample was analysed in the laboratory using liquid chromatography with tandem ...
centrino's user avatar
2 votes
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TLC experiment interprentation

I am having difficulty interpreting the results of an identification test involving six different standards (dyes) in an unknown mixture of dyes, using silica gel TLC plates and acetone as the mobile ...
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Need Suggestion for Picking the Right Solvent for Column Chromatography

I've completed my reactions, and based on the stoichiometry and TLC analysis, I think my mixture should contain 3-4 compounds: Ethyl gallate (my product) Gallic acid (the reagent/starting material) ...
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Aliphatic alcohol analysis in capillary gas chromatography

4.5. Standard solutions of trimethylsilyl ethers of aliphatic alcohols from C20 to C28. They may be prepared from mixtures of pure alcohols at the time they are required for use. Reference solution ...
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Why this problem happens on LC-MS chromatogram?

I used to analyse my compounds on LC-MSdevice with 95% water/5% acn +0,1 formic acid. My column is hypersilgold (C18). When I did my acquisition, I obtain this chromatogram sometimes, and it doesn't ...
ChemistryTryHarder's user avatar
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1 answer
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Making an UV inactive salt UV active during purification of charged anion with HILIC purification?

In the context of a purification setup I am asking myself the question: Can a UV inactive charged substance made be UV active by a counter ion that absorbs UV light during a column run? If so, when no ...
raptorlane's user avatar
14 votes
4 answers
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Does molten metal liquid chromatography exist?

Liquid chromatography is used to analyze and purify different chemical samples in a solvent. It is also used for industrial scale chemical purification. I was wondering if something similar exists for ...
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Thin layer Chromotography Separation

I am confused about the basic understanding when it comes to TLC. I was under the assumption that less polar compounds move farther on the plate due to it having fewer IMFs. But I also heard that a ...
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How can I isolate products that cannot be cleanly distilled or visualised by TLC for column chromatography?

I am a first year PhD student in the UK, and without giving too many details of my work as it is industrially funded and my sponsors are a bit touchy over IP, I am struggling to isolate the products ...
Matthew's user avatar
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When is chromatography regarded as a viable industrial purification strategy?

I understand the basics that chromatography is a fairly slow and expensive process compared to direct synthesis. When a synthesis route is not feasible, the economics become favorable. Not being in ...
ericnutsch's user avatar
3 votes
1 answer
163 views

Are there LCMS compatible buffer systems available for the high pH range 12-14?

I want to perform chemical stability studies for different pH Values. To achieve pH Values from 1 to 6 I can prepare solutions with trifluoric acid and formic acid and ammonium formate and acetate. I ...
raptorlane's user avatar
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"Is there any library in Python or software for analyzing raw chromatography data?"

I have taken the data directly from the FID sensor using a DAQ, so I have the chromatography data in this format: (2 data colummns in a txt file) (18000 rows) Time (s) Intensity (V) 0.00367___0.0008 ...
user138375's user avatar
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How do I calculate the masses of compounds in a mixture from a GC?

I'm supposed to analyse the two GC graphs in the attached picture (I quickly drew them instead of taking a picture). The question states ths "A mixture contains 3-Methylhexane. To determine the ...
Ladan's user avatar
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Regression equation for peak fronting/tailing in chromatography

Background I would like to have a sum of functions $$\sum_{i=1}^k f_i(x)$$ which approximates my chromatogram. The variable $x$ would be my retention time, although I don't mind if answers change it ...
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Term for one chromatography sample affecting the next?

Suppose I am running a collection of samples on a chromatograph (gas or liquid) in some order. Some of the sample molecules have large retention times due to their size and/or interactions with each ...
Galen's user avatar
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When creating a separation method in gas chromatography, calibration with compounds mixture or for each separate component?

When creating a separation method in gas chromatography, is there any difference between the calibration with the compounds mixture and the calibration for each separate component? I have 5 components....
DiMorten - Jorge Chamorro's user avatar
5 votes
1 answer
402 views

How to effectively replace DMSO with LC–MS-compatible solvent for the samples from a well plate?

I want to do LC–MS analysis of the samples from a 384-well plate where each compound (at around 1–10 μM) is dissolved in 10–15 μL of DMSO. I am worried about the DMSO dwarfing the analyte’s signal, as ...
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1 answer
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Is there any reason why KMnO4 for TLC is stored under basic condition?

my mentor told me that the KMnO4 solution specifically for TLC has added some bases like sodium hydroxide but we don't know why. I try to search on google, and found that the bases are usually by-...
organicrab55's user avatar
1 vote
1 answer
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How to interpret gas chromatography results?

I am having trouble interpreting gas chromatography (GC) results for the production of ethyl acetate from acetic acid and ethanol. I am trying to find the reaction order from these results, as well as ...
pulsewidth's user avatar
4 votes
1 answer
191 views

How can I approximate the actual HPLC gradient?

In High Performance Liquid Chromatography (HPLC), the actual gradient is a bit different from the true gradient programmed because of dwell volume and other effects. For example, in the figure added, ...
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How to choose the solvent gradient for the flash column chromatography of a complex mixture?

When performing a flash column chromatography, it is advised to select an eluent in which the desired compound has an $R_\mathrm{F}$ of about $0.25$ in TLC. However, if I want to separate and isolate ...
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1 vote
2 answers
286 views

How does industry separate glucose from fructose using liquid chromatography when producing high-fructose corn syrup?

Can someone explain how the separation of glucose and fructose is achieved using liquid chromatography in the industrial production of high-fructose corn syrup? I've seen references to ion-exchange ...
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Trouble analyzing amine using GC-FID

I am trying to analyze a sample containing hexamethylenediamine (HMD) dissolved in ethanol using GC-FID for an undergraduate chemical engineering project. The column used is Agilent DB-FFAP (high ...
Adam's user avatar
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2 votes
0 answers
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Dynamic equilibrium of Girard T-derivatized oxysterols

This is a question relating to organic chemistry, moreso than chromatography. I am running LC-MS on various hydroxycholesterols (HC) and dihydroxycholesterols (diHC). To increase ionization efficiency ...
Quantonium's user avatar
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1 answer
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Why I am unable to detect nystose & kestose using hplc and refractive index detector while could see peaks of glucose,sucrose,fructose, and raffinose [closed]

Mobile phase is 60% acetonitrile and temperature of the column is 25 degrees (supercosil amino from sigma). RID is also set up at 25.
Akanksha Joshi's user avatar
3 votes
1 answer
52 views

Mystery GC peak appearing between 1H2 and various molecular combinations of 1H, 2H and 3H?

The following gas chromatograph, taken from "Review of the different techniques to analyse tritium", labels all but the largest peak. Given that the analyte is likely to be from some source ...
James Bowery's user avatar
5 votes
3 answers
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Why will changing the solvent crack the column for column chromatography?

When we perform column chromatography with silica to purify the reaction crude product, we sometimes need to change the solvent system to better extract our target product. For example, changing from ...
Richie12138's user avatar
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Using Hydrogen as a carrier gas for a GC; consideration of reactivity with analytes

In many cases people use H2 as a carrier gas for a GC. But does this exclude analysis of (say) systems with unsaturation or aromatic compounds etc. If a analysis uses a temperature program say up to ...
curious_cat's user avatar
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1 vote
2 answers
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Determining volume of hydrogen gas evolved in water splitting reaction

I want to carry out a photocatalytic water spliting reaction. This reaction will generate Hydrogen and Oxygen gas in 2:1 ratio according to the following reaction - 2H2O + energy (light) → 2H2 + O2 So,...
Abdullah Shahriar's user avatar
6 votes
1 answer
800 views

What is the correct unit of a RI detector used for HPLC analysis?

I analyze sugar compounds in soft drinks with HPLC using refractive index detection (RID) on Agilent 1260 Infinity Binary LC (System User Guide (PDF)). I am not sure which unit to put next to the $y$-...
Johanna's user avatar
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2 answers
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Finding unknown concentration using HPLC standard curve

I calculated a standard curve equation from a given concentration and peak area, which gave me $y=1994.6x+218.4$. I made the graph with the $x$-axis μg/mL and $y$-axis peak area. The question is, a ...
user131308's user avatar
3 votes
1 answer
620 views

Chromatography and Height Equivalent to a Theoretical Plate (HETP)

HETP can be expressed in two ways: HETP = L/N HETP = A + B/u + Cu where: L: lenght of the coloumn N: Number of theoretical plates A: Eddy-diffusion parameter, related to channeling through a non-...
Luckenberg's user avatar
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How to change the counterion of a nucleotide salt?

I need to take the sodium nucleotide salts I have available in my lab and modify them to instead contain some more exotic counterions. Can I do this by binding my nucleotides to a strong anion ...
toodles's user avatar
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-1 votes
1 answer
202 views

Synthetic resin method to remove permanent hardness of water [closed]

Why is $\ce{R-SO3H}$ first treated with NaCl and then the RNa form i.e., the sodium form of resin is used for treating hard water? Why cannot we directly treat hard water with $\ce{R-SO3H}$? What is ...
DAYA'S SIMULATION's user avatar
2 votes
1 answer
173 views

How does having a basic stationary phase help the separation of acidic/basic compounds from non acidic/basic ones?

I have to reason whether silica or alumina would be a better choice of stationary phase for separating a mixture of pyridine and cyclohexanone with column chromatography. I would expect both pyridine ...
Baseball Fan's user avatar
1 vote
0 answers
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How to minimize sample dispersion during spotting for paper electrophoresis?

I am separating highly polar amino acids and their derivatives using paper electrophoresis. This requires pre-wetting a piece of filter paper with electrophoresis buffer (in this case, carbonate-...
Mowgli's user avatar
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1 answer
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What matters for ion exchange: net or local charge?

I am interested in separating two small organic molecules by ion exchange chromatography. Following the example set by several old papers for these molecules, I want to use a cation exchanger. Both ...
Mowgli's user avatar
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2 votes
1 answer
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What's a good high precision analysis technique (after GC) to measure trace isopropanol in water samples?

Looking to measure trace IPA content in water samples. Only GC I have access to doesn't take samples with water. Different columns not an option.
A. Anil's user avatar
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Mixture is eluted too early from alumina in flash column chromatography

I have recently tried to purify my reaction mixture by column chromatography. Because my reaction mixture had poor resolution in silica-based TLC, I used neutral alumina-based TLC plate. After I ...
Krang Lee's user avatar
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3 votes
0 answers
121 views

Why does column chromatography not work like it's supposed to?

I'm a few months into working in an organic synthesis lab and I consider myself to have a solid intuition for, well, how chemistry works. I have ran at least 50 columns at this point but no matter ...
Eric Wang's user avatar
1 vote
1 answer
70 views

Decomposable solvent identification in GC-FID

How can a gas chromatography with flame ionization detection (GC-FID) be used to identify a liquid solvent that decomposes at its boiling point like DMSO? In a solution with other higher boiling ...
Pulkit Sharma's user avatar
1 vote
0 answers
384 views

Activating alumina before column chromatography

Recently I synthesized some amine compounds, and because it showed better separation in the neutral alumina TLC plates than silica plates, I am planning to purify the reaction mixture using neutral ...
Krang Lee's user avatar
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2 votes
0 answers
61 views

How much analyte should I use for paper chromatography?

I am looking into using paper chromatography to distinguish between standard drugs and counterfeit drugs for my high school research project. I have decided on using aspirin as the "standard"...
Jiayi Shen's user avatar
1 vote
0 answers
149 views

Solvent for Terephthalic Acid TLC

We're trying to do thin layer chromatography to assess the purity of Terephthalic Acid. So far we have tried DMF, and Water of different pH values. Does anybody know a better solvent or combination?
KlausHaarmann's user avatar
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0 answers
325 views

Triethylamine is detected by ninhydrin during TLC

Continued from this question. I purchased new triethylamine from Sigma Aldrich, spotted freshly opened triethylamine to the TLC plate, dipped into ninhydrin solution, and heated it. Again the purple ...
Krang Lee's user avatar
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2 votes
1 answer
866 views

Does ninhydrin staining detect triethylamine?

My reaction mixture has amine compounds, so it shows tailing in bare silica plates. Therefore I decided to add small amount of triethylamine in the eluent. Because my amine compound is not detected by ...
Krang Lee's user avatar
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1 vote
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69 views

Corruption of TLC plates or solvent

I have been conducting TLC experiments, and sometimes I observed some lines when I use mixture of eluents. And I found that some lines are observed after I develop the TLC plates with some eluents. ...
Krang Lee's user avatar
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