Diethylhydrogensilyl-cyclic diethylsilylene derivatives in gas chromatography-mass spectrometry of prostanoids. III. F alpha-prostaglandins and thromboxane B2 derivatives.

The gas chromatographic (GC) and GC-mass spectrometric properties of the diethylhydrogensilyl-cyclic diethylsilylene (DEHS-DES) derivatives of prostaglandin (PG) F1 alpha methyl ester, PGF2 alpha methyl ester, 6-keto-PGF1 alpha methyl ester-alkyloxime and thromboxane (TX) B2 methyl ester-alkyloxime and the DES derivative of 13,14-dihydro-15-keto-PGF2 alpha methyl ester-alkyloxime were studied. When the ketonic PGs and TXB2 were converted into their methyloxime derivatives, the methylene unit values of these five prostanoid derivatives were slightly greater than those of the corresponding dimethylethylsilyl ether derivatives. When the ketonic PGs were converted into their corresponding ethyloxime derivatives, baseline separation was achieved in 20 min by use of a methylsilicone cross-linked fused-silica capillary column. The mass spectra of these derivatives were characterized by the ion at m/z 157 for F alpha prostaglandins and m/z 269 for TXB2. The major fragmentations were directed by the DES group, and other fragmentations common to the prostanoid derivatives were losses of an ethyl radical at the silicon atom, C5H11 hydrocarbon fragment, diethylhydrogensilanol and C15-C20 hydrocarbon fragment. The mass fragmentations of these prostanoid derivatives are briefly discussed. GC with high-resolution selected-ion monitoring was carried out for the TXB2 derivative at a resolution of 8000 by monitoring the ion at m/z 269.1573. A 25-pg amount of this derivative showed a well shaped doublet with a signal-to-noise ratio of more than 300:1.