Simultaneous determination of buprenorphine, norbuprenorphine, and buprenorphine–glucuronide in plasma by liquid chromatography–tandem mass spectrometry

For the first time, an LC–MS–MS method has been developed for the simultaneous analysis of buprenorphine (BUP), norbuprenorphine (NBUP), and buprenorphine–glucuronide (BUPG) in plasma. Analytes were isolated from plasma by C₁₈ SPE and separated by gradient RP-LC. Electrospray ionization and MS–MS analyses were carried out using a PE-Sciex API-3000 tandem mass spectrometer. The m/z 644→m/z 468 transition was monitored for BUPG, whereas for BUP, BUP-d₄, NBUP, and NBUP-d₃ it was necessary to monitor the surviving parent ions in order to achieve the required sensitivity. The method exhibited good linearity from 0.1 to 50 ng/ml (r²≥0.998). Extraction recovery was higher than 77% for BUPG and higher than 88% for both BUP and NBUP. The LOQ was established at 0.1 ng/ml for the three analytes. The method was validated on plasma samples collected in a controlled intravenous and sublingual buprenorphine administration study. Norbuprenorphine–glucuronide was also tentatively detected in plasma by monitoring the m/z 590→m/z 414 transition.