Diethylhydrogensilyl-cyclic diethylsilylene derivatives in gas chromatography/mass spectrometry of hydroxylated steroids. V. Analysis of cortisol and 6.BETA.-hydroxycortisol in human urine.

Abstract

A gas chromatography/selected ion monitoring (GC/SIM) method for a simultaneous determination of cortisol (Kendall's compound 'F' : F) and its hydroxylated metabolite, 6β-hydroxycortisol (6OHF) in human urine has been developed using [2H3] cortisol as an internal standard. These compounds were analyzed as their methyloxime-diethylhydrogensilyl-cyclicdiethylsilylene derivatives. Gas chromatography of the F derivative showed a fairly broad single peak, whereas the 6OHF derivative exhibited a well-resolved doublet peak corresponding to the structral syn- and anti-isomers. The mass spectra were characterized by their intense molecular ion peaks and by their inherent ions of [M-OCH3]+, [M-diethyl-hydrogensilanol (DEHSOH)]+., and [M-OCH3-DEHSOH]+. When GC/SIM was carried out using their base peak ions at m/z 559 for F and 557 for 6OHF, the sensitivity for F was about 10 pg with signal-to-noise ratio of more than 10, and this was about a 5 times higher response factor than that of 6OHF. The calibration graphs were found to be linear in the observed range covering the concentrations found in healthy human urine.