Development and validation of a simple and affordable LC-UV method for identification and assay of selected antimicrobial medicines

Antimicrobials, particularly antibiotics, are among the most common classes of drugs reported as substandard and falsified (SF) in developing countries. Therefore, it is important to develop simple and affordable analytical methods for the quality control of antimicrobial medicines. In this study, a liquid chromatographic method with ultraviolet detection (LC-UV) was developed and validated for the screening and quantification of 13 antimicrobial medicines and one beta-lactamase inhibitor in pharmaceutical formulations. LC separation was carried out on a Kinetex C18 column (150mm × 4.6mm, 2.6µm) with gradient elution. The mobile phase consisted of mixtures of acetonitrile-water-10 mM phosphate buffer pH 3.5 at ratios of 3:92:5, v/v/v for mobile phase A and 50:45:5, v/v/v for mobile phase B with a flow rate of 0.5mL/min. The screening method was intended for confirmation of the identity of the actives and validated for specificity and robustness, whereas the quantification method (using only a different detection wavelength) was further validated in terms of linearity, accuracy, sensitivity and precision (repeatability, intermediate precision). For all compounds, the method was found to be linear (r2 > 0.999), precise (%RSD < 1%), accurate (% recovery of 98-102%), sensitive, specific and robust. The developed LC method was successfully applied for the identification and assay of 12 antimicrobial samples from Ethiopia. Among the 12 samples analyzed, one (8.3%) product was confirmed to be falsified.