By jezkova on Wednesday, July 2, 2003 - 12:38 am:
Hi,
I analyze stearic acid and hydrocarbons in my samples. Please, could you give me an advice how to eliminate incomplete derivatization probably caused by traces of water byproduct formed during the reaction.
Samples are dissolved in pyridine, which is dried. Derivatization is done by BSTFA. Sometimes I have observed white crystals in my samples formed after derivatization. After that peak of unsilylated acid was present in chromatogram. Also , according GC-MS analysis, N,N-diethyloctadecanamid was in my products - How can be it formed?
Thank You, Iva
By Soap Chemist on Wednesday, July 2, 2003 - 07:58 am:
I work for a soap company; we use trimethylsilation (BSTFA) routinely, and have published on its applications. Many of our samples contain up to 85% water, and we don't have any trouble, as long as we make sure to have excess BSTFA. We routinely derivatize fatty acids. In your case, solublizing in pyridine (good choice), I wouldn't bother to dry the sample at all: why?
By jezkova on Sunday, July 13, 2003 - 11:09 pm:
Thank you very much,
Iva
By Uberto on Tuesday, July 15, 2003 - 09:53 pm:
Iva,
You may use MTBSTFA for derivatization. The t-butyldimethylsilyl ester is more hydrolytically stable c.f. TMS ester, as the latter will be hydrolysed back when water is present.