A new reliable and rapid HPLC method for the simultaneous determination of amoxicillin and sulbactam pivoxil in pharmaceuticals. Application to both assay and dissolution samples

Abstract

A fast, efficient and simple high performance liquid chromatographic method was developed and validated for the simultaneous determination of amoxicillin trihydrate (AMO) and sulbactam pivoxil (SP) in oral pharmaceutical dosage forms and, eventually, for their dissolution tests. The difference in molar absorptivities of these compounds constituted an analytical challenge, especially in formulations where AMO was in a higher proportion than SP. A reverse phase C18 column was used with a mobile phase consisting of acetonitrile and water (80:20 v/v) in isocratic mode. The retention times were found to be 2.26 min and 1.34 min for SP and AMO, respectively. The linearity range was evaluated over the concentration range of 2.5 and 250.0 µg mL-1 (correlation coefficients higher than 0.9998). The method was validated according to the International Conference on Harmonization ICH guidelines regarding selectivity, linearity, accuracy, precision, limit of detection, limit of quantification, system suitability and robustness. The validated method was applied for the quantification of AMO and SP in commercial tablets and oral suspensions (AMO/SP ratio between 1:1 and 7:1), being the first method in the open literature that enables the correct quantification of both active ingredients in formulations with an AMO/SP ratio higher than 1:1. Also, the new method was successfully applied for the dissolution study of AMO/SP formulations, which was reported for the first time in the open literature. According to the obtained results, the proposed method can be applied in the quality control of pharmaceuticals containing a combination of amoxicillin and sulbactam pivoxil.