Comparative study of the derivative and partial least squares methods applied to the spectrophotometric simultaneous determination of atorvastatin and amlodipine from their combined drug products

The simultaneous spectrophotometric determination of Atorvastatin calcium (ATV) and Amlodipine besylate (AML) in tablets in the presence of the overlapping spectra was accomplished with the derivative spectrophotometry (DS) and the partial least squares (PLS) approaches without using any chemical pre-treatment. In this study, the concentration model was based on the absorption spectra in the range of 220-400 nm for 25 different mixtures of ATV and AML. The calibration curve was linear over the concentration range of 10-160 and 3-33 mu g mL(-1) for ATV and AML, respectively. These two methods were tested by analyzing the synthetic mixtures of the above drugs and they were applied to the real samples, containing two commercial pharmaceutical preparations of the subjected drugs. A comparative study was carried out using the experimental results obtained from the two analytical methodologies. The root mean squares differences (RMSD) with PLS and DS were 0.6618 and 1.2555 for ATV and 0.1589 and 0.3490 for AML, respectively. It should also be mentioned that the accuracy of the PLS method was better than that of DS.