Determination of Morphine, Fentanyl and Their Metabolites in Small Sample Volumes Using Liquid Chromatography Tandem Mass Spectrometry.

The USA and numerous other countries worldwide are currently experiencing a public health crisis due to the abuse of heroin and illicitly manufactured fentanyl. We have developed a liquid chromatography tandem mass spectrometry (LC-MS-MS)-based method for the detection of morphine, fentanyl and their metabolites, including morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G), normorphine, norfentanyl and deuterated internal standards in limited sample volumes with the limit of detection of 5.0/0.5 ng/mL (morphine, M3G, M6G, normorphine/fentanyl, norfentanyl). The inter-assay precision (%CV) was less than 12% for all assays, and the inter-assay bias (%) was less than 5%. The ruggedness of the method, dilution effect and carryover were also investigated as part of the study. The simultaneous quantification of morphine, fentanyl and its metabolites via this simple and time- and cost-efficient method could be successfully applied to samples taken for pharmacokinetic evaluation (antemortem and postmortem) after a single dose of morphine or co-administration of morphine with other drugs (e.g., fentanyl) in rats.