Low-level quantitation of oxycodone and its oxidative metabolites, noroxycodone, and oxymorphone, in rat plasma by high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry

A method was developed for quantification of oxycodone, noroxycodone, and oxymorphone in small volumes (50 μl) of rat plasma by high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry using turbo ion-spray. Deuterated (d3) opioid analogues acted as internal standards. Sample preparation involved protein precipitation with acetonitrile, centrifugal evaporation, and reconstitution in mobile phase; analyte separation was performed on a C18 (5 μm, 2.1 mm × 50 mm) column using a linear gradient program. Lower limits of quantitation (ng/ml) and their between-day accuracy and precision were—oxycodone, 0.9 (−0.2 and 7.8%); noroxycodone, 1.0 (0.6 and 6.2%); oxymorphone 1.0 (−1.8 and 9.5%).