Gas chromatographic-mass spectrometric quantitation of urinary buprenorphine and norbuprenorphine after derivatization by direct extractive alkylation.

A gas chromatographic-mass spectrometric procedure for the quantitation of buprenorphine and norbuprenorphine has been developed in which the analytes were converted, after enzyme hydrolysis, to their methyl derivatives by direct extractive alkylation using tetrahexylammonium hydrogen sulphate phase transfer reagent and iodomethane dissolved in tert.-butylmethyl ether. The procedure utilised a sample volume of 2 ml and gave a detection limit of 0.2 ng ml(-1) for buprenorphine and norbuprenorphine. The buprenorphine and norbuprenorphine standard curves were linear in the concentration range of 1-100 ng ml(-1) with r=0.999. The coefficients of variation for the intra-run precision were 1.3% for buprenorphine and 8.8% for norbuprenorphine (n=10). The coefficients of variation for the inter-run precision were 7.7% for buprenorphine and 10.1% for norbuprenorphine (n=5). The method recovery was 92% (C.V.=3.3%) for buprenorphine and 104% (C.V.=2.9%) for norbuprenorphine (n=10).