QUANTIFICATION OF THE ANTI-HIV DRUG SAQUINAVIR BY HIGH-SPEED ONLINE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY

A method is described for the fast routine determination of the anti-H IV drug saquinavir and its pentadeuterated analogue [H-2(5)] saquinavi r in the plasma of healthy volunteers. The method is based an high-per formance liquid chromatography (HPLC)/atmospheric pressure positive-io n chemical ionization (APCI) mass spectrometry, with a stable labelled form of saquinavir (C-13(6)-H-2(3)-N-15) as internal standard. Automa ted solid-phase extraction in combination with short-column HPLC and m ultiple reaction monitoring is employed for high selectivity and sensi tivity, and this also permits rapid quantification (the run time per s ample is 1.5 min) over the range of 0.4-200 ng ml(-1) with excellent a ccuracy and precision. Up to 200 samples per analyst per day can be an alysed. This assay methodology illustrates the versatility of APCI tan dem mass spectrometry, in conjunction with high-speed HPLC, for the fa st routine quantification of drugs in the nanograms per millilitre ran ge, which is essential for clinical pharmacokinetic studies.