I am attempting to derivatize amino acids in the form of N-pivaloyl-i-propyl esters using a published method. One of the last sample preparation steps (after adding pivaloylchloride) involves passing the sample through a 200-400 mesh silica gel column (I have the silica gel and can prepare a column using a pasteur pippette).

I assume the gel is used to separate the derivatized amino acids from the nasty excess of pivaloylchloride, which I wouldn't want in the GC. The problem is that both materials are colourless and thus difficult to differentiate as they are separated down the gel column. Can anyone offer advice as to how to I could separate these materials? Would the pivaloylchloride simply adhere to the silica gel, leaving the derivatized amino acids to pass through and be collected? The other way around? If they are simply separated but both pass through, how might I ensure they are collected separately?

Any help/advice would be greatly appreciated!!