Quantitative analysis by liquid chromatography-tandem mass spectrometry of deuterium-labeled and unlabeled vitamin E...

A method for quantification of unlabeled alpha-tocopherol and the deuterated tocopherols, RRR-alpha-5-(CD(3))-tocopherol (d(3)RRR) and all rac-alpha-5,7-(CD(3))(2) tocopherol (d(6)all-rac) in plasma by HPLC-tandem mass spectrometry (LC-MS/MS) has been developed. Deuterated and unlabeled alpha-tocopherols were separated by HPLC and were detected by positive ion multiple-reaction monitoring using a triple-quadrupole mass spectrometer equipped with a heated nebulizer-atmospheric pressure chemical ionization interface, following routine extraction of vitamin E from plasma. The accuracy and precision were evaluated by replicate analysis of standards and samples. Human plasma samples, which were obtained at different times after the subject had consumed a capsule containing 1:1 ratio of d(3)RRR and d(6)all rac-alpha-tocopheryl acetates, were analyzed with this method. Plasma deuterated alpha-tocopherols measured by LC-MS/MS followed the same pattern as previously demonstrated by GC-MS measurement, without requiring an extra derivitization step. The detection limit was 10 pmol for each form of alpha-tocopherol injected.