Quantitative determination of the HIV protease inhibitor atazanavir (BMS-232632) in human plasma by liquid chromatography–tandem mass spectrometry following automated solid-phase extraction

A selective, accurate, and reproducible LC–MS–MS assay was developed for the determination of the HIV protease inhibitor atazanavir (BMS-232632) in human plasma samples. The method involved automated solid-phase extraction of atazanavir and a stable isotope analog internal standard (I.S.) using Oasis HLB 10 mg 96-well SPE plates. A portion of the reconstituted sample residue was injected onto a C18 HDO analytical column which was configured with a triple quad mass spectrometer for analyte determination by positive ion electrospray. The assay was linear from 1.00 to 1000 ng/ml with a lower limit of quantitation of 1.00 ng/ml. The inter- and intra-day coefficients of variation (C.V.) for the assay were <4%, and the accuracy was 99–102%. Atazanavir was stable in human plasma for at least 109 h at room temperature and for at least 1 year at −20 °C.