Use of new silylating agents for identification of hydroxylated steroids by gas chromatography and gas chromatography mass spectrometry.

Differences in methylene unit values were used for the determination of the hydroxyl group number of a steroid by means of gas chromatography. This index is defined as the difference in the methylene unit value between trimethylsilyl and other dimethylalkylsilyl (DMAS) ether derivatives of hydroxylated steroids, namely dimethylethylsilyl (DMES) and dimethyl-n-propylsilyl (DMPS) ethers. The reactivities of DMES and DMPS imidazoles as silylating agents were nearly equal to that of TMS-I. Mass spectra of these derivatives were characterized by the molecular ion cluster, [M]+., [M-15]+ and [M-29]+ (or [M-43]+). The molecular ion cluster of these derivatives is most useful for estimating the molecular weight. Therefore, these DMAS ethers provide valuable information for structural elucidation of hydroxylated steroids by gas chromatography electron impact mass spectrometry.