Simultaneous determination of bambuterol and its two major metabolites in human plasma by hydrophilic interaction ultra-performance liquid chromatography–tandem mass spectrometry

•A HILIC–UPLC–MS2 method for analysis of bambuterol and its metabolites in plasma was developed.•Application to a clinical pharmacokinetics study of bambuterol.•The effects of chromatographic conditions on the HILIC retention were investigated.•The benefits of HILIC were evaluated by comparing with C18 ligands.

In this study, a rapid and sensitive hydrophilic interaction ultra-performance liquid chromatography–tandem mass spectrometry (HILIC–UPLC–MS/MS) method was developed for simultaneous determination of bambuterol and its two major metabolites monocarbamate bambuterol and terbutaline in human plasma. All samples were simply precipitated using acetonitrile and separated on a UPLC-HILIC column under gradient elution with a mobile phase consisting of acetonitrile and water with the addition of 10 mm ammonium acetate and 0.1% formic acid at 0.4 mL/min. The analytes were detected by a Xevo TQ-S tandem mass spectrometer with positive electrospray ionization in multiple reaction monitoring mode. The established method was highly sensitive with the lower limit of quantification (LLOQ) of 10.00 pg/mL for each analyte, and the intra- and inter-day precisions were <12.8%. The analytical runtime within 4.0 min per sample made this method suitable for high throughput determination. The validated method was successfully applied to a clinical pharmacokinetic study of bambuterol in eight healthy volunteers. Furthermore, the effects of the chromatographic conditions on the retention of the analytes on HILIC were investigated, and the benefits of HILIC were evaluated by comparing with a C18 column. The results indicated that liquid–liquid partition and the electrostatic interactions played an important role in the retention of the analytes on HILIC in this study. And HILIC offered particular advantages over RPLC approach in the aspects of the peak symmetry, the column efficiency, and the column pressure.