Simultaneous determination of chlorthalidone and spironolactone with univariate and multivariate calibration: Wavelength range selection

Chlorthalidone and spironolactone were determined simultaneously with the a id of univariate and multivariate calibration methods. Univariate calibrati on was performed by the zero-crossing and derivative ratio spectrum methods . Extensive spectral overlap and the scarcity of wavelengths in derivative spectra allowing one analyte to be distinguished and quantitated in the pre sence of the other gave rise to poor results that called for multivariate c alibration. Partial least-squares regression was used in combination with a suitable method for selecting the optimum wavelength range and number of f actors for analysis. The ensuing method was applied to simultaneous determi nation of chlorthalidone and spironolactone in a commercially available pha rmaceutical preparation. The results were validated by high-performance liq uid chromatography.