Evaluation of ceftazidime contents in antibiotic discs by capillary electrophoresis

Good quality of antibiotic discs is a fundamental prerequisite to accurate antibiotic susceptibility tests. Capillary electrophoresis (CE) is a widely used method for quantitative analysis. Here, using ceftazidime as an example, we report an easy-to-perform strategy to determine ceftazidime content in discs. First, a serial of ceftazidime standard solutions was prepared to determine the detection linearity. Utilizing the background buffer containing 50 mmol/L Na2HPO4, 0.045 mmol/L beta-cyclodextrin and 3.15 mmol/L Tris (hydroxymethyl) aminomethane, ceftazidime of concentrations ranging from 1.875 to 60 microg/ml showed a linear response to detected peak areas. Subsequently, four kinds of ceftazidime discs were selected from different manufacturers. The discs were homogenized using 1 ml deionized water, and then detected by CE after filtration. The results showed that one kind of discs were of poor quality as further confirmed by disc diffusion tests using standard strains. This study proved the potential of CE as an easy choice to perform disc quality control under appropriate conditions.