Muhammad Naeem Khan

Development and Validation of a New Spectrophotometric Method for the Determination of Cephalexin Monohydrate in Pure Form and Pharmaceutical Formulations

A simple, fast, sensitive and accurate spectrophotometric method has been developed for the quantitative determination of cephalexin monohydrate in dosage form and in commercial formulations. The method involves the addition of CeIV to cephalexin in acidic medium, followed by the determination of residual CeIV by reacting with a fixed amount of methyl orange, and the absorbance was measured at 510 nm. Beers law was obeyed in the concentration range of 0.6-20 µg mL-1 with correlation coefficient of 0.992. The molar absorptivity was calculated and was found to be 9.8 × 104 L mol-1 cm-1. Different variables affecting the reaction conditions such as concentration and volume of CeIV, type and concentration of acids used, reaction time and temperature were carefully studied and optimized. The limit of detection (LOD) and limit of quantification (LOQ) were calculated and found to be 0.221 and 0.736 µg mL-1, respectively. The proposed method was found to have good reproducibility with a relative standard deviation of 4.4% (n = 9). The interference effects of common excipients found in pharmaceutical preparations were studied. The developed method was validated statistically by performing recoveries studies and successfully applied for the determination of cephalexin in bulk powder and pharmaceutical preparations. Percent recoveries were calculated and found to range from 90.6 to 102.9% for bulk powder and from 98.7 to 104.8% for pharmaceutical preparations.