Simultaneous spectrophotometric determination of sulfamethoxazole and trimethoprim in rmaceutical preparations by using multivariate calibration methods

The uv-speetrophotometric method of analysis was proposed for simultaneous determination of sulfamethoxazole and trimethoprim. considering the strong spectral overlap among uv-vis spectra of these compounds, a previous separation should be carried out in order to determine them by conventional spectrophotometric techniques. here, full-spectrum multivariate calibrations pls and pcr methods arc developed. the experimental calibration matrix was constructed with 26 samples . the concentration ranges considered were 2-15 μgml^-1 sulfamethoxazole and 0.4-6 μgml^-1 trimethoprim.absorbance data of the calibration standards were taken between 200-400nm with uv-vis spectrophotometer. for achieving the best model, related parameters of the model were evaluated. the optimum number of factors was selected by using the cross-validation method. the relative errors in each step were calculated. the pls and pcr calibrations based on the raw data matrix were utilized to illustrate successfully the application of the proposed methods for analy sis of the drugs in synthetic mixture s and pharmaceutical tablet. the errors obtained in the pls method were slightly better. the errors were less than 0.1% for sulfamethoxazole and 0.9% for trimethoprim in pls method, respectively.