Analysis of fentanyl and norfentanyl in human plasma by liquid chromatography-tandem mass spectrometry using electrospray ionization.

This report describes a sensitive and specific high-performance liquid chromatography (HPLC)-electrospray ionization-tandem mass spectrometry (MS-MS) method for the detection of subnanogram concentrations of fentanyl and its metabolite norfentanyl in human plasma. The assay was based on a liquid-liquid extraction of 0.5 mL of human plasma, with a lower limit of quantitation (LLOQ) of 0.05 ng/mL. Sample extracts were analyzed using a ThermoQuest TSQ MS-MS interfaced with a Hewlett-Packard series 1100 HPLC and a Phenomenex (30 x 2.00-mm, 5 microLuna C18(2)) column. The intra-assay precision and accuracy ranged from 2.1 to 12.5% for both analytes at concentrations of 0.1, 0.5, 1.0, and 10 ng/mL. The interassay accuracy and precision ranged from 7.34 to 10.95%.