I am studying biochemistry and I have been asked by my teacher to find a procedure for separating cellulose, starch, the peptide oxytocin (9 a.a) and palmitic acid ($\ce{C16}$) using gel filtration chromatography. I have some ideas about using Fehling's test to tell the cellulose from the starch and the peptide since they all react with the $\ce{Cu^{2+}}$ in the solution. And I'm thinking that the palmitic acid will not dissolve in the solution and can therefore be separated from the others.

However, I have a problem with how the gel filtration would work. Obviously cellulose and starch are much bigger than palmitic acid and oxytocin but, how could I possibly separate cellulose from starch using gel filtration??

Gel filtration: https://en.wikipedia.org/wiki/Size-exclusion_chromatography

  • $\begingroup$ Are you sure you have to use gel filtration for this? Cellulose might be the right size for gel filtration, but starch is normally not soluble and the two smaller molecules, oxytocin and palmitic acid will probably elute in the void volume. $\endgroup$ – VonBeche Dec 8 '16 at 17:03

I think by using a gradient mobile phase that changes by time. At the beginning, the mobile phase would have higher affinity to cellulose and lower to starch and then the gradient changes where it would have higher affinity to starch than cellulose.

Specifically, which mobile phase you would use and what gradient would take some time and research to find the answer but it think you get the idea

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    $\begingroup$ Using a gradient on a gel filtration column doesn't really work. $\endgroup$ – VonBeche Dec 8 '16 at 16:53

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