RESUMO
Two multivariate calibration methods, partial least squares (PLS-2) and principal component regression (PCR) have been applied to the simultaneous spectrophotometric analysis of ternary mixtures of phenytoin (DPH), phenobarbital (PBT) and methylphenobarbital (MPBT) in the Comital-L pharmaceutical formulation. The PLS-2 and PCR procedures were employed to evaluate the data of a variable number of calibration solutions measured over the wavelength range 400-700 nm. The concentration ranges used to construct the calibration matrix were varied between 5 and 30 microg ml(-1). The proposed methods were validated by applying them to the analysis of the Comital-L pharmaceutical formulation and the average relative errors were less than 6% for each one of the analyzed compounds. The results obtained by both proposed methods have been compared with the results obtained by application of a RPLC reference method.