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Topic: Paper Chromatography (and TLC)  (Read 9872 times)

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Ice_cool

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Paper Chromatography (and TLC)
« on: February 26, 2006, 08:37:09 AM »
Hello

I am doing a project comparing Thin Layer Chromatography and Paper Chromatography. There are 2 questions I would like to ask and I would be very grateful if you could answer as soon as possible (I will be starting my project tommorrow)

1. For the amino acid separation (using Paper Chromatography and TLC) the solvent (eluent) I will be using is a 90:10 mixture of ethanol and ethanoic acid.
For the carbohydrate separation the solvent will be Isopropyl (propan-2-ol) - the sugars that are being separated are fructose, glucose, sucrose and lactose (see below). Do you think Isopropyl is a good solvent to use? Any suggestions?

2. I am going to be separating samples which contain Amino Acids and Carbohydrates. The Amino Acid sample I will be using is Orange Juice, and the Carbohydrate sample will be Coca-Cola (because of the different sugars). Now, do you think Coca Cola is a bad sample to use because of the acid? I am thinking of using Ribena (a sugary blackcurrant drink which contains glucose, fructose and sucrose apparantly). The actual pure Carbohydrate samples I will be using are Glucose, Fructose, Sucrose and Lactose. So do you think Ribena is a good idea?

3. One more question if you don't mind! I know I have to dissolve my sample (e.g. orange juice) in a solvent, and then spot it. Now, does this solvent have to be the same as the eluent? Or can it be any solvent?

I really appreciate any help you could give me!

Thank you!

 :)
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Offline Yggdrasil

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Re:Paper Chromatography (and TLC)
« Reply #1 on: February 28, 2006, 04:45:35 PM »
Quote from: Ice_cool on February 26, 2006, 08:37:09 AM
Hello

I am doing a project comparing Thin Layer Chromatography and Paper Chromatography. There are 2 questions I would like to ask and I would be very grateful if you could answer as soon as possible (I will be starting my project tommorrow)

1. For the amino acid separation (using Paper Chromatography and TLC) the solvent (eluent) I will be using is a 90:10 mixture of ethanol and ethanoic acid.
For the carbohydrate separation the solvent will be Isopropyl (propan-2-ol) - the sugars that are being separated are fructose, glucose, sucrose and lactose (see below). Do you think Isopropyl is a good solvent to use? Any suggestions?

Carbohydrates are very polar compounds and I'm not sure that they would be soluble in a solution of isopropanol.  If the isopropanol doesn't resolve the sugars, try using a mixture of an alcohol (methanol, ethanol, or isopropanol) with water.

Quote
2. I am going to be separating samples which contain Amino Acids and Carbohydrates. The Amino Acid sample I will be using is Orange Juice, and the Carbohydrate sample will be Coca-Cola (because of the different sugars). Now, do you think Coca Cola is a bad sample to use because of the acid? I am thinking of using Ribena (a sugary blackcurrant drink which contains glucose, fructose and sucrose apparantly). The actual pure Carbohydrate samples I will be using are Glucose, Fructose, Sucrose and Lactose. So do you think Ribena is a good idea?

Does orange juice really have that many amino acids in it?  I would suspect that orange juice is mostly carbohydrates (sugars) and acids (citric and ascorbic).  The acid probably won't be a problem unless you're using a basic stationary phase (e.g. alumina) which might react with the acid in the samples.

Quote
3. One more question if you don't mind! I know I have to dissolve my sample (e.g. orange juice) in a solvent, and then spot it. Now, does this solvent have to be the same as the eluent? Or can it be any solvent?

As long as you let the spot evaporate before you run the chromatography, it doesn't matter what solvent you spot your samples with.  Since it seems like most of your samples are liquid (i.e. disolved in water), you just need to let the water evaporate off before performing the chromatography.

I hope this response (albeit a little late) can be of some help.
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Ice_cool

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Re:Paper Chromatography (and TLC)
« Reply #2 on: March 01, 2006, 05:47:13 PM »
yggdrasil

hello, I greatly appreciate your help  ;D  It wasn't too late at all!

AFAIK, there are a few amino acids in the orange juice.

The rest of your post was useful. Thanks a lot!

 ;D
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Ice_cool

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Re:Paper Chromatography (and TLC)
« Reply #3 on: March 04, 2006, 05:58:16 AM »
hello
 
Could I ask a few more questions if that is okay (btw, I am doing an ongoing project which is lasting a few weeks)

1. Should the solvent for paper chromatography (of amino acids) be the same as the solvent for TLC (of amino acids)?

2. Also, for the TLC of sugars, is silica gel okay to use as a stationary phase?
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Offline Yggdrasil

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Re:Paper Chromatography (and TLC)
« Reply #4 on: March 04, 2006, 07:58:03 PM »
1.  The solvent will not necessarily be the same.  The migration of compounds in a chromatography experiment is dependent on the moleclues' affinity for the stationary phase and their affinity for the mobile phase (solvent).  If you change your stationary phase, you may also need to adjust the solvent.

2.  Try it and find out.  If you can't get an adequate separation of your sugars on silica, you can try using different solvent or stationary phases.  Note that it may be difficult to separate different disaccharides (fructose, sucrose, and lactose) from eachother because they have similar sizes and polarities.  However, separating disaccharides from monosaccharides (e.g. glucose) shouldn't be as difficult.
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