Dimethylisopropylsilyl ether derivatives in gas chromatography-mass spectrometry of some prostanoids : Application to the microdetermination of 15-ketoprostaglandin F 2α formed by enzymatic conversion of PGF 2α in vitro

Abstract

Treatment of 15-ketoprostaglandin F 2α (15-keto-PGF 2α) with ethereal diazomethane at −78°C provided only the expected methyl ester (ME), without the formation of the pyrazoline adduct. The electron-ionization mass spectrum of the dimethylisopropylsilyl (DMiPS) ether derivative of 15-keto-PGF 2α ME showed the molecular ion, and the characteristic fragment ion of [M−43] + was of high abundance. The appearance of these ions in the high-mass region made it possible to determine trace amounts of 15-keto-PGF 2α in biological specimens without any interference from endogenous substances. The detection limit for the DMiPS ether derivatives of 15-keto-PGF 2α ME was 12 pg (signal-to-noise ratio = 10). The method was applied to the analysis of 15-keto-PGF 2α obtained by the enzymatic conversion of PGF 2α with 15-hydroxyprostaglandin dehydrogenase in vitro.