QUANTITATIVE-DETERMINATION OF F-6-1,25(OH)(2)VITAMIN D-3, IN HUMAN SERUM BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY WITH HIGH-RESOLUTION SELECTED-ION MONITORING

A highly sensitive and specific gas chromatographic/mass spectrometric method was developed for the determination of very low levels of F-6- 1,25(OH)(2) vitamin D-3, a new fluoro analogue of vitamin D-3, to faci litate investigation of its pharmacokinetics in man. Deuterium-labelle d F-6-1,25(OH)(2) vitamin D-3 was employed as an internal standard for quantification. The method involves extraction from serum samples, se paration by a cartridge column system followed by straight-phase high- performance liquid chromatography, O-trimethylsilylation, and analysis by gas chromatography/mass spectrometry using high-resolution selecte d ion monitoring, With a quantification limit of 2 pg ml(-1) and a req uirement for 2 ml of serum, the assay method has sufficient sensitivit y, selectivity and precision for the analysis of very low concentratio ns of the drug.