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.

ABSTRACT

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 10mM ammonium formate and acetonitrile (6832, 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.