Direct analysis of opiates in urine by liquid chromatography-tandem mass spectrometry

A method for the direct analysis of 10 opiate compounds in urine was developed using liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS) with electrospray ionization interface (ESI). Opiates included were morphine-3-β- glucuronide, morphine-6-β-glucuronide, morphine, oxymorphone, hydromorphone, norcodeine, codeine, oxycodone, 6-monoacetylmorphine (6MAM), and hydrocodone. Urine samples were prepared by centrifugation to remove large particles and direct injection into the LC-MS-MS. Separation and detection of all compounds was accomplished within 6 min. Linearity was established for all opiates except 6MAM from 50 ng/mL to 10,000 ng/mL; 6MAM from 0.25 ng/mL to 50 ng/mL with all correlation coefficients (r) > 0.99. Interrun precision (%CV) ranged from 1.1% to 16.7%, and intrarun precision ranged from 1.3% to 16.3%. Accuracy (% bias) ranged from -7.3% to 13.6% and -8.5% to 11.8 for inter- and intrarun, respectively. Eighty-nine urine samples previously analyzed by gas chromatography-MS were re-analyzed by the LC-MS-MS method. The qualitative results found an 88% agreement for negative samples between the two methods and 94% for positive samples. The LC-MS-MS method identified 19 samples with additional opiates in the positive samples. Overall, the direct injection LC-MS-MS method performed well and permitted the rapid analysis of urine samples for several opiates simultaneously without extensive sample preparation.