Spectrophotometric and Spectrofluorimetric Methods for Simultaneous Estimation of Amlodipine and Metformin in Bulk and Synthetic Mixture

Purpose: the purpose of this article is to develop two simple, rapid, accurate and economical spectrophotometric methods and a sensitive spectrofluorimetric method for the simultaneous estimation of amlodipine (AD) and metformin (MT) in bulk and synthetic mixture.

Method: The Spectrophotometric determination involved simultaneous equations method that measured the absorbances of both the drugs at 238 nm (λ_max of metformin) and at 361 nm ( λ_maxof amlodipine) and Q- absorbance ratio method that measured the absorbance of both the drugs at 238 nm (λmax of metformin) and at isoabsorptive point (256 nm). A spectrofluorimetric determination is based on the reaction between the drugs and 1- dimethylaminonaphthalene-5-sulphonyl chloride (Dansyl chloride) in presence of 1 M sodium carbonate (pH 10) to yield a highly fluorescent derivative that is measured at 450 nm and 520 nm after excitation at 345 nm for AD and MT, respectively. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized.

Results and discussions: Both spectrophotometry methods showed linearity over the range of 5-90 μg ml^-1 for AD and 1-10 μg ml^-1 for MT. The fluorescence intensity were linear over the range of 0.1-3.5 μg ml^-1 for AD and 0.05-1.3 μg ml^-1 for MT. Results of analyses were validated statistically and through recovery studies.