COMPARATIVE STUDY AMONG FOUR SPECTROPHOTOMETRIC METHODS FOR THE SIMULTANEOUS DETERMINATION OF BINARY MIXTURE OF CHLORZOXAZONE AND DICLOFENAC POTASSIUM

Four simple, fast, accurate, reproducible, and non-sophisticated spectrophotometric methods were developed and validated for the simultaneous determination of chlorzoxazone and diclofenac potassium without preliminary separation in pure powder form and in their capsule formulation. Method A, is a dual wavelength spectrophotometric method in which the wavelengths selected for determination of chlorzoxazone were 259 nm and 294 nm, whereas the wavelengths selected for determination of diclofenac potassium were 294 nm and 242 nm. while method B, is a ratio difference spectrophotometric method in which the wavelengths selected for determination of chlorzoxazone were 280 nm and 230 nm, whereas the wavelengths selected for determination of diclofenac potassium were 246 nm and 284 nm. while method C, is the first derivative of the ratio spectra measured at 290 nm and 301 nm for chlorzoxazone and diclofenac potassium, respectively. While method D, is the constant center spectrophotometric method in which more measured at 280 nm and 277 nm for chlorzoxazone and diclofenac potassium, respectively. Regression analysis of Beer-Lambert’s plots showed good correlation in concentration range of 2.5 – 20 μg/mL for both drugs with LOD 0.308 μg/mL and 0.932 μg/mL, LOQ 0.458 μg/mL and 1.388 μg/mL, RSD 1.325 and 1.666 and % recovery 98.99 and 101.23 for chlorzoxazone and diclofenac potassium, respectively in method A. Furthermore, LOD 0.307 μg/mL and 0.373 μg/mL, LOQ 0.929 μg/mL and 1.123 μg/mL, RSD 1.065 and 1.371 and % recovery 99.94 and 101.53 for chlorzoxazone and diclofenac potassium, respectively in method B. Furthermore, LOD 0.287 μg/mL and 0.301 μg/mL, LOQ 0.871 μg/mL and 0.911 μg/mL, RSD 1.214 and 1.596 and % recovery 99.73 and 100.26 for chlorzoxazone and diclofenac potassium, respectively in method C. Furthermore, LOD 0.221 μg/mL and 0.331 μg/mL, LOQ 0.521 μg/mL and 0.825 μg/mL, RSD 0.914 and 1.412 and % recovery 101.22 and 98.59 for chlorzoxazone and diclofenac potassium, respectively in method D. The suggested methods were validated in compliance with the ICH guidelines and were successfully applied for determination of chlorzoxazone and diclofenac potassium in their laboratory prepared mixtures and commercial capsule formulation.