Solid-phase microextraction for the detection of codeine, morphine and 6-monoacetylmorphine in human hair by gas chromatography-mass spectrometry

Introduction: Opiate hair analysis continues to prove difficult due to the scarcity of hair sample and low drug concentrations. For this reason, we developed a sensitive method utilizing headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) for the detection of three principle opiates; codeine, morphine, and 6-acetylmorphine. Methods: Experimental conditions for HS-SPME and GC-MS were systematically optimized to produce the sensitive analytical method reported. Briefly, opiates were extracted from adult hair with methanol under agitation. The methanolic extract was then decanted into SPME autosampler vials, where deuterated standards of each of the 3 opiates were added at a concentration of 2 ng/mg. Samples were dried under N₂, derivatized, and subjected to HS-SPME coupled with GC/MS for analysis. Results: Preliminary datum for this study indicates detection limits for these 3 opiates are superior to that reported in the literature; an LOQ of 0.01 ng/mg for morphine and 6-acetylmorphine and 0.005 ng/mg for codeine. Linearity was evident between 0.01 ng/mg and 5 ng/mg for each opiate, with R² above 0.992. The robustness of the method was demonstrated to be acceptable as inter-day and intra-day precision fell below 15% for each opiate analyzed. Conclusion: Compared with conventional methods, this method of detection for opiates is fast, simple, and accurate, with the sensitivity and specificity required in forensic and clinical toxicology.