[TLC] Analysis of amino esters by TLC

[seacrd]

Hi everyone,

I have a problem whenever I try to analyze alpha-amino esters by TLC. Since these esters are obtained from the amino-acid, I use systems which are suitable for the starting amino-acid, such as butanol-acetic acid-water. My concern is that I always see traces (about 1%) of starting aminoacid on the TLC plate, and I know for sure that it does not come from my sample. I guess the ester hydrolyses a bit on the silica during the migration.

Does anyone have any experience with this type of compounds ? Any idea of a TLC system that would not hydrolyse my ester ?

Thanks in advance.

PS : I forgot, of course the amino esters are as HCl salts.

[HW Mueller]

One would expect a smear if one has a reaction on the plates. One can imagine that the HCl of your salt will do something before application to the plate.
How do you make the esters?

[seacrd]

Usually it's aminoacid + alcohol + thionyl chloride.
When I say that I know there is no acid left in my sample, I mean I have spotted samples which I know were free of the acid (either from a catalogue with CofA, or after checking by HPLC-UV when there is a chromophore).