Simultaneous determination of amoxicillin and clavulanic acid in human plasma by HPLC with UV detection

A simple and accurate high-performance liquid chromatographic method with ultraviolet detection at 220 nm has been validated for the simultaneous determination of amoxicillin and clavulanic acid in human plasma. Plasma samples were pretreated by direct deproteinization with methanol. A good chromatographic separation between both compounds was achieved using a reversed phase C8 column and a mobile phase, consisting of acetonitrile-phosphate solution-tetramethyl ammonium chloride solution. The calibration curves were linear over the concentration range of 0.625–20 mg l −1 for amoxicillin and 0.3125–10 mg l −1 for clavulanic acid with determination coefficients >0.998. The method is accurate (bias