Simultaneous determination of monoacetylmorphine, morphine, codeine, and other opiates by GC/MS

A GC/MS method for the simultaneous determination of morphine, codeine, and O-6-monoacetylmorphine as well as other semisynthetic opiates in urine is described. The method employs 2H6-acetic anhydride to acetylate free hydroxyl groups on all of the opiates. As a result, the same hydrolysis and extraction procedure is used for all analytes. Quantitation is achieved using gas chromatography/mass spectrometry in the electron impact mode and with selected ion monitoring of the three most characteristic ions for each analyte. Ratios of these three ions are used for verifying identity while the molecular ions are used for quantitation. The detection limit for all analytes is less than 10 ng/mL.