silylation slow

[beate]

Hello,

developing a GC-method for alkanolamines I have the following problem: for better chromatography I have derivatize them.
I use MSTFA with 10 % TMCS to make a silylation. The problem is, the reaction is rather slow, I have done some tests and measuerd the peaks after 2 up to 6 hours reaction time at 80 °C, the peak is still growing at the end of the time. The maximum is achieved when I measure the next day and the vials stood at room temperature over night. This is not practical solution.
The effect is different for different amines, so an internal standard would not help.
I added the TMCS as the reaction is better then, I tested at 70 °C and 80 °C, the increasing temperature has not such a big impact.
Has anyone another idea to boost this reaction?
Thanks a lot,

Beate

[krickos]

Hi

One reagent that I have used a few times on amines with good results is MTBSTFA.
It is strong/fast yet kind of mild silylatin reagent, known to complete reaction upon dissolution or very short time in oven (~20min at 60°C).
A small addition of dry pyridine may help.

MTBSTFA+ 1% t-BDMCS can help with hindered alcohols and amines.

[Consumer Products Guy]

Like krickos suggested: use pyridine as solvent, and some heat, that's what we use when we derivatize alkanolamines. The hydrogen on an oxygen derivatizes readily, but replacing the H on the nitrogen is more difficult, and pyridine acts as a hydrogen acceptor.

[Consumer Products Guy]

Like krickos suggested: use pyridine as solvent, and some heat, that's what we use when we derivatize alkanolamines. The hydrogen on an oxygen derivatizes readily, but replacing the H on the nitrogen is more difficult, and pyridine acts as a hydrogen acceptor.