Application of a classical least-squares regression method to the assay of 1,4-dihydropyridine antihypertensives and their photoproducts.

A multicomponent UV spectrophotometric method using a classical least-squares (CLS) algorithm has been developed for the quantitative determination of 1,4-dihydropyridine (DHP) calcium antagonists and respective photoproducts. The procedure was optimized by defining a fractionation scheme for selecting the more useful wavelength ranges to be used in the calibration model. The method is potentially able to be extended to the other drugs of the same family.

Photodegradation monitoring of amlodipine by derivative spectrophotometry.

A derivative spectrophotometric method for the simultaneous determination of amlodipine and its pyridine photodegradation product has been developed. The analytes concentrations were linearly correlated with spectral measurements in the 3rd order UV derivative spectrum through equations obtained by simple and multiple regression analysis. The recovery values were estimated to range from 95 to 99% and the quantitation limit of the photoproduct was found to be equivalent to an impurity level of 1%, with respect to the content of amlodipine.