GC/MS/MS quantification of 11-dehydrothromboxane B2 in human urine.

A fully validated stable isotope dilution method for rapid quantification of 11-dehydrothromboxane B2 by gas chromatography/negative chemical ionization tandem mass spectrometry is reported. The interassay coefficient of variation was 1.3%. The relative recovery of synthetic, underivatized 11-dehydrothromboxane B2 added to urine was 84.6 +/- 2.5% (mean +/- SEM, N = 9). The equation of the regression plot correlating the amounts added and recovered was Y = 0.894X-0.23, with R = 0.9963. The late introduction of the pentafluorobenzyl moiety at C11 afforded distinct advantages in the cleanup stage of the assay and during the GC/MS analysis as well. The pair of daughter fragments at m/z 345 and 349 of the parent fragment ions at m/z 615 and 619 were monitored. Excretion values of 11-dehydrothromboxane B2 in 3 healthy male subjects were 975, 615 and 822 ng/24 h. Excretion was reduced to 751, 387 and 465 ng/24 h, respectively, after administration of a fish oil supplement (15 g/day) for 10 weeks.