Spectrophotometric Determination of Chlorzoxazone and p-Acetaminophenol in Chlorozoxazone Compound Tablets by Absorbance-Ratio Method

It was reported that from the absorbance-ratio spectral curve,the wavelength pair for the determination of chlorzoxazone (CRXZ) and p-acetaminophenol (ACAP) was chosen as 215.7 nm and 264.1 nm. The calibration curve was prepared by determining the absorbance of a set of mixed standard solutions of CRXZ and ACAP of appropriate concentrations at the wavelengths given above,then calculate the values of absorbance ratio R and ΔR according to the formula given in the paper,and finally the linear regression equations of ΔR against concentration of CRZX or of ACAP were established. In the analysis of chlorxazone compound tablets,a definite amount of the sample was taken and dissolved in the solvent and diluted to a definite volume with the same solvent. An aliquat of the solution was taken and treated in the same way as in the preparation of calibration curve. From the absorbance values obtained,calculate the values of ΔR and find the corresponding concentrations from the regression equations. In the test for precision and recovery of this method RSD′s (n=7) obtained for CRXZ was 1.28% and for ACAP was 0.84%,and average recoveries were 100.0% for both constituents.