Twenty-fifth anniversary of the retention index system in gas—liquid chromatography

The dimethylisopropylsilyl ether derivatives of PGF1α and PGF2αmethyl esters and PGD2, PGE1, PGE2, 6-Keto PGF1α and thromboxane B2 methoxime-methyl esters were separated completely within 15 min by gas chromatography using open tubular glass capillary column coated with SE-30. The methylene unit values of these derivatives were slightly greater than those of the corresponding dimethyl-n-propylsilyl ether derivatives. The use of the dimethylisopropylsilyl ether derivatives made it possible to perform the baseline separation of PGs and thromboxane B2 which were not separated by the trimethylsilyl ether derivatives. The mass spectral fragmentation of these dimethylisopropylsilyl ether derivatives was similar to those of the corresponding trimethysilyl ether derivatives, reported in a previous paper. Their mass spectra were characterized by the molecular ion, [M]+., and the ions [M—15]+ and [M—43]+ like those in the hydroxysteroid dimethylisopropylsilyl ether derivatives reported previously. The ion [M—34]+, which is produced by the elimination of isopropyl group from [M]+., was observed as an intense peak. The appearance of this ion in the high mass region was very useful for quantitation of trace amounts of PGs and thromboxane B2 in biological fluids without disturbance of endogenous substances by selected ion monitoring. The detection limit of the dimethylisopropylsilyl ether derivative of PGF2α methyl ester was found to be 5 pg with a signal-to-noise ratio of 10:1 when monitoring the ion [M—43]+ (m/z 625).

Dimethylisopropylsilyl ether derivatives in gas chromatography mass spectrometry of prostaglandins and thromboxane B2

The analytical approach described allows for the rapid screening and concurrent quantitative determination of all of the major metabolites of the cyclooxygenase pathway of arachidonic acid, including the primary prostaglandins PGE2, PGD2 and PGF2 alpha in addition to the stable end-products of short-lived prostacyclin and thromboxane A2 (6-keto-PGF1 alpha and TXB2, respectively), generated by incubating arachidonic acid with mouse peritoneal macrophage cells. After derivatization into the corresponding methyl ester-methoxime-TMS derivative, the extracted endogenous compounds were analysed by combined high efficiency glass capillary column chromatography and selected ion monitoring. Comparatively lower detection limits can be achieved with the methyl ester-butylboronate-TMS derivatives (e.g. 10 pg for 6-keto-PGF1 alpha). A brief account is also presented on a new type of mixed methyl ester-pentafluorobenzyloxime-butylboronate-TMS derivative of TXB2 and 5-keto-PGF1 alpha.

Quantitative profiling of the metabolic cascade of arachidonic acid by capillary gas chromatography mass spectrometry

Prostaglandins E and F, and 19-hydroxylated E and F (series I and II) in semen of fertile men. Gas and liquid chromatographic separation with selected ion detection.

J. Rosello

Papers

Profiles of prostaglandins A, B, E and F (series I and II) obtained by gaschromatography with multiple-ion detection