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Chromatograph

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Chromatograph

Postby Waters2 » Tue May 24, 2005 12:46 pm

Can i ask that why must the starting line contain the drops of concentrated spot (e.g chlorophyll or food dye) solution be placed above the solvent level at the begining?? And what the steps to ensure the effective separation??? Can anyone tell me pls??
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Postby MrMistery » Tue May 24, 2005 6:19 pm

I only know it for chlorophil but i guess this goes for everything
That solvent of yours is highly volatile. It evaporates very easly and in the 30 minutes that you keep your paper over the solvent the paper becomes almost saturated in solvent molecules. If you do not do this and insert the paper directly into the solvent it will migrate too much and that green spot will simply move from the bottom to the top of the paper
Last edited by MrMistery on Tue May 24, 2005 8:16 pm, edited 1 time in total.
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Postby Jelanen » Tue May 24, 2005 8:06 pm

You need the solvent level to be below the level of your drops so that your drops don't dissolve into the solvent pool. If the solvent level is below the drops then when the solvent is pulled up the film by capillary action, the samples will be carried along for the ride and separated according to size, mass, density, etc. To ensure effective separation, run the (thin layer) chromatography as long as possible WITHOUT letting the solvent front reach the end of the film.

At least I'm pretty sure that answers your question(s)

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Postby MrMistery » Tue May 24, 2005 8:18 pm

Actually Jelanen, the practical papers of botany book says too keep it over the solvent for 30 minutes and then put it 5 milimeters into the solvent until the pigments migrate. Trust me, i have done this for my national olympics
PS: thanks again for that "volatile" thing and i appologise
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Postby Jelanen » Tue May 24, 2005 10:54 pm

I guess it depends on the particular technique. Never did anything like you are saying when it did it a couple dozen times in organic chemistry. It was always put on drops, drop in sealed bottle with solvent at bottom, wait (eating late lunch usually), remove from bottle, interpret data. Might be different for planty people, but I'm not one of those.....
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Postby MrMistery » Wed May 25, 2005 7:12 pm

planty people... Lool... I guess i am one of those...
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Postby Waters2 » Wed May 25, 2005 10:36 pm

Thanks for information, and i have another question?? Why the thin layer of filter paper keep away from the wall of the container when u put the paper into the container and also in the process of chromatograph???
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