Quantitative determination of the major metabolite of prostaglandins F1α and F2α in human urine by stable isotope dilution and combined gas chromatography-mass spectrometry

Abstract An improved gc-ms method has been developed for the measurement of 5α,7α- dihydroxy - 11 - ketotetranorprosta - 1,16 - dioic acid (PGF-M), the major urinary metabolite of PGF 1α and PGF 2α in man. The assay is based on gas chromatography and selected ion monitoring mass spectrometry, employing a specifically deuterated analog of the metabolite, labeled in the cyclopentane ring, as internal standard. The analytical procedure involves extraction from urine, methylation and selective hydrolysis at pH10 to afford the PGF-M 16-monomethyl ester. Dehydration of this compound to the corresponding δ-lactone methyl ester and subsequent solvent extraction effects a substantial purification of the urinary extract. Following conversion to its t-BDMS ether methyl ester derivative, the metabolite is purified by thin-layer chromatography and analyzed by gas chromatography-mass spectrometry. Measurements of urinary PGF-M in the normal range of 5–40 ng/ml may be made with 2% precision from a 10 ml sample while the lower limit of detection is in the order of 1 ng/ml.