A solid phase extraction technique for the isolation and identification of opiates in urine

A quantitative method was developed for the simultaneous analysis of morphine, codeine, hydromorphone, hydrocodone, and oxycodone in urine by gas chromatography/mass spectrometry. Samples were hydrolyzed with beta-glucuronidase and then extracted by solid phase extraction on Bond Elute Certify cartridges at pH 6.8. Nalorphine was used as the internal standard. The opiates were analyzed by full-scan electron impact GC/MS after derivatization with acetic anhydride-pyridine. The standard curves for all five drugs were linear between 50 and 1000 ng/mL, with correlation coefficients exceeding 0.99. Coefficients of variation were less than 7%. The method was applied to the analysis of postmortem urines positive by EMIT opiate assay, and the effect of the hydrolysis procedure on recovery of each drug was measured. The results indicate that the hydrolysis procedure is effective in increasing the recovery of all five drugs from urine. The described method enables the laboratory to identify the five opiates most commonly encountered in forensic and clinical laboratories. Its sensitivity for all five drugs is well below GC/MS cutoffs for codeine and morphine employed in NIDA laboratories, and it provides for conclusive full-scan drug identification.