[Simultaneous determination of amoxicillin and clavulanic acid in the human plasma by high performance liquid chromatography-mass spectrometry (UPLC/MS)].

BACKGROUND/AIM Quantitative analysis of amoxicillin and clavulanic acid in biological matrices requires sensitive and specific methods which allow determination of therapeutic concentration in 1 g/mL range. Analytical methods for determination of their concentrations in body fluids described in literature include high performance liquid chromatography coupled to UV detector (HPLC-UV) and liquid chromatography-mass spectrometry (LC-MS). The aim of this study was to develop sensitive and specific ultra performance liquid chromatography/mass spectrometry (UPLC/MS) method which could be used for the spectral identification and quantification of the low concentrations of amoxicillin and clavulanic acid in the human plasma. METHOD A sensitive and specific UPLC/MS method for amoxicillin and clavulanic acid determination was developed in this study. The samples were taken from the adult healthy volunteers receiving per os one tablet of amoxicillin (875 mg) in combination with clavulanic acid (125 mg). RESULTS Plasma samples were pretreated by direct deproteinization with perchloric acid. Quantification limit of 0.01 microg/ml for both amoxicillin and clavulanic acid was achieved. The method was reproducible day by day (RSD < 7%). Analytical recoveries for amoxicillin ranged from 98.82% to 100.9% (for concentrations of 1, 5 and 20 microg/mL), and recoveries for clavulanic acid were 99.89% to 100.1% (for concentrations of 1, 2 and 5 microg/mL). This assay was successfully applied to a pilot pharmacokinetic study in healthy volunteers after a single-oral administration of amoxicillin/clavulanic combination. The determined plasma concentrations of both amoxicillin and clavulanic acid were in the range of the expected values upon the literature data for HPLC-UV and LC-MS methods. CONCLUSION The described method provided a few advantages comparing with LC/MS-MS method. The method is faster using running time of 5 minute, has lower limit of quantification (LOQ) and it could be used in pharmacokinetic studies of both amoxicillin and clavulanic acid.