An isocratic ion exchange HPLC method for the simultaneous determination of flucloxacillin and amoxicillin in a pharmaceutical formulation for injection

An isocratic ion exchange high performance liquid chromatography method was developed for the simultaneous determination of flucloxacillin and amoxicillin in pharmaceutical formulations for injections. The separation was made by a ZORBAX 300-SCX column using 0.025 M ammonium dihydrogen phosphate (adjusted to pH 2.6 with phosphoric acid)-acetonitrile (95:5) as mobile phase. The validation of the method was performed, and specificity, reproducibility, precision and accuracy were confirmed. The limits of quantification were approximately 0.2 μg/ml for each drug. Due to its simplicity and accuracy the method is particularly suitable for routine pharmaceutical quality control.