Purification and quantitative analysis of urinary prostanoids in human and in rat by packed and capillary gas chromatography-negative-ion chemical-ionization mass spectrometry.

We describe a method for the quantitative analysis of prostaglandin (PG) E2 and the major urinary metabolites PGI2 and thromboxane (Tx) A2 in human and in rat by combined gas chromatography and negative-ion chemical-ionization mass spectrometry. The procedure is based on the sequential use of small columns with distinct properties combined with a thin-layer chromatography step, for the extraction and the purification of urinary prostaglandins. The compounds are then analysed as their pentafluorobenzyl ester-O-methyloxime-trimethylsilyl ether derivatives, using either packed or capillary columns. Deuterated analogues are used as internal standards. The method was established by using tritiated prostaglandins covering the extremes of polarity in order to optimize the recovery of prostanoids as well as the quality of the chromatograms and spectra. The overall recovery was 24%. Standard curves were obtained by the same procedure and found to be reproducible, with a maximal day-to-day variation of +/- 5%. The relatively simple approach required for the sequential extraction and purification of prostaglandins on small columns of distinct properties, combined with the highly specific and highly sensitive method of detection, places this procedure among the most reliable method for measuring urinary prostanoids in both humans and animals. In addition, the procedure is faster than classical approaches and necessitates smaller amounts of samples and solvents.