Questions tagged [chromatography]
collective term for a set of laboratory techniques for the separation of mixtures
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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 ...
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Would decreasing the percentage of ethyl acetate increase the polarity? [closed]
I was doing practice problems to prepare for an upcoming test and I came across the problem above. I wrote that the answer was C since that would increase the polarity of the hexane, thereby making it ...
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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 ...
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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
...
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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 ...
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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 ...
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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....
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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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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-...
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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 ...
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HPTLC Densitogram - Not Showing Other Secondary Metabolites
I have run a HPTLC analysis of methanolic extract of Gymnema Sylvestre R.Br. plant in order to determine the concentration of active ingredient (Gymnemic acid using Gymnemagenin as standard). Sample ...
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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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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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,...
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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 $y$-...
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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 ...
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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-...
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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 ...
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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 ...
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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 ...
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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-...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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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"...
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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?
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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 ...
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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 ...
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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. ...
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Fragmentation behavior of spots in TLC
I tested multiple development using eluent condition hexane + 1% of ethyl acetate. Then I observed kind of fragmentation of spot.
I'm not sure, but I guess that successive spots are from the skyblue ...
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Ion Exchange chromatography [closed]
Suppose that Anion exchanger is used in the stationary phase
normally -ve charge A.A will be eluted first as it will not attach
but my question is does the zwitter ion(have net charge 0 will be the ...
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Using neutral or basic alumina in column chromatography for purification of amines
I am conducting a synthesis involving amines, and it is found that some spots still hardly moves from the starting point in spite of the dichloromethane 9:methanol 1 eluent condition. Addition of ...
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Can I expect the same (or very close) peak areas from herbal extracts prepared with the same plant/solvent ratio?
I prepared an extract by using 100 mg of plant and 2 mL of ethanol, filtered and injected 20 μl into the HPLC system equipped with Waters® XSelect (150 mm × 4.6 mm, 5 μm) column. If I prepare an ...
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Can I scrape off compounds from normal TLC like in prep TLC for MS analysis?
As far as I know, the limit of detection of mass spectrometry is very low compared to other analysis. In principle, so I think I can scrape off some compounds from normal TLC plate after development ...
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TLC monitoring of Buchwald-Hartwig coupling reaction using ninhydrin stain
I am conducting a synthesis involving Buchwald-Hartwig coupling reaction. The reagents are 2,3,5-tribromothiophene, 1-aza-18-crown-6, NaOtBu as base, $\ce{Pd_2(dba)_3}$ as palladium source, DavePhos ...
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Separation of very nonpolar mixtures using column chromatography
I am conducting a synthesis using Buchwald-Hartwig coupling. Below is the TLC result after nearly all consumption of limiting starting material. Th is 2,3,5-tribromothiophene, which is the limiting ...
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How can I determine the purity of an oligonucleotide solution?
After desalting an oligonucleotide via gel chromatography, I am left with (presumably) an oligonucleotide substance suspended in a buffer. What is the simplest way to verify the oligonucleotide's ...
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Why can I extract all metabolites from blood plasma with one solvent, but to extract only fatty acids I must use many solvents?
I want to do a metabolite study using GC- without derivatization and UPLC-MS (RP and NP) on samples of plasma and urine. My hypothesis is agnostic about which metabolite will correlate with the ...
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Interpretation of permanganate-stained TLC spots
When I stain TLC spots with $\ce{KMnO4}$, I found that some spots appear differently as time goes by. Here is the example:
The leftmost one is the plate right after staining, and the others are ...
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