Quantitative method for analysis of hydrocodone, hydromorphone and norhydrocodone in human plasma by liquid chromatography-tandem mass spectrometry.

A selective, sensitive and accurate high-performance liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for the quantitation of hydrocodone, hydromorphone and norhydrocodone in human plasma was developed. The internal standard stock solution comprised of hydrocodone-d6, hydromorphone-d6 and norhydrocodone-d3 was added to 0.5 mL plasma samples. Samples were extracted using a copolymeric sorbent (mixed mode) solid phase extraction (SPE) column. Chromatographic separation was carried out using a reversed-phase C18 analytical column with a gradient mobile phase consisting of solvent A=5% acetonitrile with 0.1% formic acid and solvent B=100% acetonitrile. MS analysis was performed using positive electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. Linearity was established over the range 1-100 ng/mL with correlation coefficients ≥0.998 for all three analytes. The coefficient of variation (CV) of intra-day samples was ≤5.6% at 10 ng/mL. The precision of inter-day (6 days) samples resulted in CVs ≤8.1% at concentrations tested at 2.5, 10 and 25 ng/mL for all three analytes. The lower limit of quantification (LOQ) was 1.0 ng/mL with signal-to-noise (S/N) ratio >10, the limit of detection (LOD) was 0.25 ng/mL with S/N ratio >3 for the drug and its metabolites. Dilution effects, extraction recovery, stability, interference, carryover and ion suppression were also evaluated. This method was successfully applied to human subject plasma samples in support of a hydrocodone pharmacokinetic study.