Simultaneous determination of codeine, morphine, hydrocodone, hydromorphone, oxycodone, and 6-acetylmorphine in urine, serum, plasma, whole blood, and meconium by LC-MS-MS

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for simultaneous analysis of six major opiates in urine, serum, plasma, whole blood, and meconium is described. The six opiates included are codeine, morphine, hydrocodone, hydromorphone, oxycodone, and 6-acetylmorphine (6-AM). The method was compared to an in-house gas chromatography (GC)-MS method and an LC-MS-MS method performed by another laboratory. The sample preparation time was decreased by eliminating the glucuronide hydrolysis and derivatization required for GC-MS analysis, as well as by adapting the solid-phase extraction to elute directly into autosampler vials. These improvements illustrate the advantages of an LC-MS-MS method over a GC-MS method for opiates. The structural similarity of these six opiates and others in the opiate class causes a high potential for interference and false-positive results. Twelve opiate analogues and metabolites were evaluated for interference. The potential for interference was reduced by altering the MRM transitions chosen for the six opiates. The increased specificity of LC-MS-MS decreased the interference rate in urine to 3.9% compared to 13.6% on the in-house GC-MS method. The rate of positivity for 6-AM in meconium is described for the first time. In urine, 11.0% of morphine positive specimens were also positive for 6-AM compared to 8.3% in serum/plasma and 0.9% in meconium. Although 6-AM is infrequent in meconium, it provides a definitive proof of illegal heroin abuse by the pregnant mother. This method has been routinely used in our laboratory over the last 6 months on more than 1500 patient specimens.