Determination of buprenorphine and norbuprenorphine in hair by GC-MS

Buprenorphine is a synthetic derivative of thebaine used as a substitute of heroin in detoxification programs. Buprenorphine was introduced for this application in May 2000 in Italy and its use for this therapeutic purpose has increased by over than 30% in three years. The aim of this study was to extend the method routinely applied in our laboratory to detect heroin metabolites, cocaine and amphetamines also to buprenorphine (BPR) and its metabolite norbuprenorphine (norBPR) in order to monitor BPR administration in detoxification programs as well as to detect drug abuse during detoxification. The analytical procedure was as follows: after a washing-step with methanol, hair was finely cut and incubated in HCl 0.1N (45°C, overnight). Nalorphine was chosen as internal standard. Purification of analytes was executed by solid phase extraction (Bond Elut Certify) which provided recoveries higher than 80% for both BPR and norBPR; purified extract was derivatised with N-methyl, N-trimethylsilyl trifluoroacétamide (MSTFA) and the analysis was performed by GC-MS in SIM mode. Ions monitored were: m/z 450, 482, 506 for BPR, m/z 468, 500, 524 for norBPR and m/z 455. 414, 324 for internal standard (underlined ions were used as quantifiers). Method validation was performed by: evaluation of accuracy and precision; analysis of seven drug-free hair samples; testing of linearity (0-0.5 ng/mg, n = 5). Intra-day (n = 7) and inter-day (n = 3 on 5 different days) precision were better than 8.8%for both analytes and accuracy better than 15%. The limit of detection was 0.005 ng/mg and the limit of quantitation was 0.01 ng/mg. This method was applied to hair samples collected from patients in withdrawal treatment programmes and demonstrated its good applicability in routine analysis.