Microdetermination of the 6,15-diketo-13,14-dihydroprostaglandin F1alpha in human plasma using gas chromatography/selected ion monitoring with [18O]6,15-diketo-13,14-dihydro-prostaglandin F1alpha as an internal standard.

We devised a simple and effective purification method for the microdetermination of 6,15-diketo-13,14-dihydro-prostaglandin F1alpha (DK), a metabolite of prostacyclin (PGI2). [18O]DK was synthesized from the repeated base-catalyzed hydrolysis of methyl ester derivatives in [18O] water to obtain an internal standard for the gas chromatography/selected ion monitoring (GC/SIM) of DK. The methyl ester-methoxime-tert-butyldimethylsilyl ether derivative was prepared, then gas chromatography/selected ion monitoring was carried out by monitoring the ion at m/z 613.4 for DK and at m/z 617.4 for an internal standard. A good linear response over the range of 10 pg to 10 ng was demonstrated. We detected DK to a level of about 297.8 pg/ml in human plasma. This method can be used to determine DK in biological samples.