Simultaneous determination of flucloxacillin and ampicillin in human plasma by ultra performance liquid chromatography–tandem mass spectrometry and subsequent application to a clinical study in healthy Chinese volunteers

A novel method has been developed for the simultaneous determination of flucloxacillin and ampicillin in human plasma by ultra performance liquid chromatography combined with tandem mass spectrometry (UPLC–MS/MS).The plasma was treated by single step of protein precipitation (PPT) with acetonitrile. The chromatographic separation was performed with a mobile phase consisting of 10 mM ammonium formate and acetonitrile (68:32, v/v). The analyses were carried out by multiple reaction monitoring (MRM) using the precursor-to-product combinations of m/z 454.1 → 160.3 (flucloxacillin), m/z 350.1 → 106.4 (ampicillin) and m/z 436.1 → 277.3 (IS).Validation results indicated that the lower limit of quantification (LLOQ) were both 0.2 μg/mL and both assay exhibited a linear range of 0.2–500 μg/mL. The intra-batch precision (R.S.D.) was less than 10.6% and inter-batch R.S.D. was less than 11.2%, while accuracy was with ±8% and ±9.9%, determined from QC samples for flucloxacillin and ampicillin.A rapid, sensitive and specific method for simultaneous quantifying flucloxacillin and ampicillin in human plasma have been devised and successfully applied to a clinic pharmacokinetic study.

► In this study, we have developed a novel method by UPLC–MS/MS.
► We simultaneous determined flucloxacillin and ampicillin in plasma.
► The method has the superiority for high sensitivity and a short run time.
► The method has been successfully applied to its pharmacokinetic study.