All Questions
Tagged with chromatography organic-chemistry
67
questions
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39
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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)
...
- 155
1
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62
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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 ...
1
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64
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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 ...
- 11
1
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1
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197
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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-...
- 11
2
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148
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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 ...
user78790
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87
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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 ...
- 21
2
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58
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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 ...
- 341
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3
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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 ...
- 469
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47
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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 ...
- 137
2
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1
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174
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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 ...
- 41
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1
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147
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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 ...
- 183
3
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121
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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 ...
- 31
2
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61
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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"...
- 47
1
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84
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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 ...
- 1,101
2
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809
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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 ...
- 1,101