Gas chromatographic-mass spectrometric profiling with negative-ion chemical ionization detection of prostaglandins and their 15-keto and 15-keto-13,14-dihydro catabolites in rat blood

A method was set up in which the primary prostaglandins (PGF2 alpha, PGD2, PGE2, thromboxane B2, 6-keto-PGF1 alpha and 6-keto-PGE1) and their catabolites (15-keto and 15-keto-13,14-dihydro) could be analyzed in the same sample at the same time. The method makes use of long capillary columns (60 m) to resolve the complex mixture during gas chromatography and mass fragmentography to provide the specificity of detection of these products. Selectivity and sensitivity is provided through use of appropriate derivatives (pentafluorobenzyl esters) which allow detection by negative-ion chemical ionization in which high-abundance fragments in the high end of the mass spectrum (M-pentafluorobenzyl) are observed. A purification procedure of whole blood is described involving diethyl ether extraction, C18 Sep-Pak chromatography, derivatization into the pentafluorobenzyl-O-methyloxime, C18 Sep-Pak and silicic acid chromatography followed by final derivatization into trimethylsilyl ethers for gas chromatographic-mass spectrometric analysis. Recovery of added 3H]PGF2 alpha was 73.8 +/- 2.2% (n = 10). Sample workup and analysis takes ten days for six samples. The method is sufficiently sensitive for the profiling of a 10-ml sample of whole blood (limit approximately 1 pg/ml; 1-pg injection on column).