Mass spectrometry for clinical bioanalysis without chromatographic separation: bioequivalence for bupropion and its metabolites

High-throughput solid-phase extraction coupled with tandem mass spectrometry (HT-SPE-MS/MS) is an automated sample delivery system to mass spectrometry that operates without chromatographic separation. The typical analysis time per sample using this platform is 10-30 s. While the HT-SPE-MS/MS system has demonstrated efficacy for in vitro assays, its application to the analysis of biological samples from in vivo bioavailability and bioequivalence studies presents challenges due to the complexity of the sample matrix. Three critical issues - matrix effect, specificity, and carryover - have not been thoroughly evaluated in complex biological matrices such as plasma. This study assessed the feasibility of utilizing HT-SPE-MS/MS for the analysis of three metabolically related compounds (bupropion, hydroxybupropion, and threobupropion) in human plasma samples from a clinical bioequivalence study. Critical bioanalytical parameters, including matrix effect, specificity, accuracy, precision, and carryover, were systematically investigated. These methods were subsequently applied to a bioequivalence study of bupropion. The HT-SPE-MS/MS approach achieved comparable accuracy, precision, linearity, and sensitivity to conventional ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) methods, while offering 20- to 30-fold higher analysis speeds. The results of this study indicate that the HT-SPE-MS/MS system shows potential for high-throughput in vivo bioanalysis, particularly in bioavailability and bioequivalence studies.