Abstract
The present study describes the development of a microwell spectrophotometric method with high throughput for determination of macrolide antibiotics; erythromycin (ERM) and josamycin (JOS) were used as representative examples. The method employed the charge-transfer (CT) reaction between each of ERM and JOS (as electron donors) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as a p-electron acceptor. The proposed method employed 96-microwell assay plates for carrying out the reaction and the color signals were measured at 450 nm by microwell-plate reader. The optimum conditions for the proposed method were established. Under these conditions, Beer's law was obeyed in the concentration ranges of 10-160 and 10-100 mu g/well for ERM and JOS, respectively. The limits of detection and quantitation were 4.6 and 13.8 mu g/well for ERM and 3.41 and 11.36 mu g/well for JOS, respectively. The precisions of the method were satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the analysis of pharmaceutical formulations of ERM and JOS with good accuracy and precision. The results of the proposed method were compared favorably with those of reference methods. The method described herein is of great practical value in pharmaceutical analysis of macrolide antibiotics because it offers a high analytical throughput and consumes minimum volumes of organic solvents. Therefore, it decreases the exposures of the analysts to the toxic effects of organic solvents and reduces the analysis cost. Although the method was validated for ERM and JOS, the same methodology could be used for any macrolide antibiotic as all of the members have electron-donating capability and thus can exhibit CT reaction.