Quantitative determination of paclitaxel and its metabolites, 6α-hydroxypaclitaxel and p-3'-hydroxypaclitaxel, in human plasma using column-switching liquid chromatography/tandem mass spectrometry.

A column-switching liquid chromatography/electrospray ionization tandem mass spectrometry to determine paclitaxel and its metabolites, 6α-hydroxypaclitaxel and p-3'-hydroxypaclitaxel, in human plasma was developed. The analytical system had a Shim-Pack MAYI-ODS (10 × 4.6 mm i.d.) trapping column with deproteinization ability that concentrates analytes and removes water-soluble components. This method covered a linearity range of 5-5000 ng/mL of concentrations in plasma for paclitaxel, a range of 0.87-870 ng/mL for 6α-hydroxypaclitaxel and a range of 0.87-435 ng/mL for p-3'-hydroxypaclitaxel. The intra-day precision and inter-day precision of analysis were less than 11.1%, and the accuracy was within ±14.4% at concentrations of 5, 50, 500 and 5000 ng/mL for paclitaxel, 0.87, 8.7, 87 and 870 ng/mL for 6α-hydroxypaclitaxel, and 0.87, 8.7, 87 and 435 ng/mL for p-3'-hydroxypaclitaxel. The total run time was 30 min. Our method was successfully applied to clinical pharmacokinetic investigation.