Online solid-phase extraction liquid chromatography–electrospray-tandem mass spectrometry analysis of buprenorphine and three metabolites in human urine

An online solid-phase extraction (SPE) liquid chromatography–electrospray tandem mass spectrometry (LC–ESI-MS/MS) method for the determination of buprenorphine (Bup), norbuprenorphine (nBup), buprenorphie-3-β-d-glucuronide (Bup-3-G) and norbuprenorphie-3-β-d-glucuronide (nBup-3-G) in human urine was developed and validated. A mixed mode SPE column with both hydrophilic and lipophilic functions was used for online extraction. A C18 column was employed for LC separation and ESI-MS/MS was utilized for detection. Buprenorphine-D4 (Bup-D4) and norbuprenophine-D3 (nBup-D3) were used as internal standards for quantitative determination. The extraction, clean-up and analysis procedures were controlled by a fully automated six-port switch valve. Identification and quantification were based on the following transitions: m/z 468→414 for Bup, m/z 414→364 for nBup, m/z 644→468 for Bup-3-G and m/z 590→414 for nBup-3-G, respectively. Good recoveries from 93.6% to 102.2% were measured and satisfactory linear ranges for these analytical compounds were determined. Minimal ion suppression effect (∼7% response decrease) was determined. Intra-day and inter-day precision showed coefficients of variance, CV, ranged from 3.3% to 10.1% and 4.4% to 9.8%, respectively. Accuracy ranging from 97.0% to 104.0% was determined. The applicability of this newly developed method was demonstrated by analyzing human urine samples from the patients in Bup treatment program for therapeutic monitoring purpose.