The measurement of 13,14-dihydro-15-keto prostaglandin E2 by combined gas chromatography mass spectrometry.

THe main metabolite of prostaglandin E2 (PGE2) 13,14-dihydro-15-keto-PGE2 readily dehydrates and can subsequently form a cyclic derivative. This problem can be overcome by the immediate formation of oximes of the 9 and 15 ketones in aqueous solution followed by subsequent extraction, methylation and t-butyldimethyl silylation of the free hydroxyl groups at 11 and on the oximes. Deuterogenated 13,14-dihydro-15-keto-PGE2 is used as the internal standard and can be stored as the oxime and added with the oximating solution immediately the biological sample is obtained. The sensitivity of the method allows measurement of 2 ng of 13,14-dihydro-15keto-PGE2 in tissue incubates. The intra-batch precision is 11.8% and the inter-batch precision for measurement of 100 ng of metabolite is 8.1%.