by
Rndirk » Wed Jan 03, 2018 1:59 pm
kvirkler wrote:
We are well aware of the conversion to nordiazepam when it is analyzed underivatized as that seems to be well documented. It looks like the heat of the injector port is the problem, and other benzos have a similar issue which is why you have to derivatize.
I thought derivatization in your case was necessary to make it volatile enough for GC, like in most cases where you derivatize.
Are you sure the amine oxide function group of demoxepam, where the magic happens, is derivatized? How many silyl groups are added during the derivatization? Is enough silation agent added? If this function is not, or only partially, protected it means that you could still have conversion in the injector port.
Something else I was thinking about (and maybe easier to check) is to substitute ethyl acetate for another solvent (acetonitrile, acetone,..). While ethyl acetate is not the same as acetic anhydride, it can still be a source of acetylation in some conditions. Or it could contain impurities as the source of your problems (acetic acid, water,..). In any case you should definitely stick to high purity solvents.