Three simple and sensitive methods were developed for the determination of a mixture of amlodipine besilate (AM) and valsartan (VL) without prior separation. In methods (A), (B) and (C), AM was determined by the application of direct spectrophotometry technique and measuring its zero-order absorption spectra at 360 nm. While in method (A), VL was determined by the application of first derivative of ratio spectra technique (1DD) and measuring its amplitude at 255.5 and 290 nm. Method (B) was based on isosbestic point technique, where the total content of the mixture was determined at their isosbestic point at 242 nm, while the content of AM was determined as mentioned at 360 nm. Thus the content of VL could be calculated by subtraction. Method (C) was depended on the use of a new and precise ratio subtraction technique for the determination of VL at its λmax 250 nm in presence of AM, while the latter was determined as mentioned at 360 nm. Linearity range was 4 – 64 µg/ml for both AM and VL for the three methods. Since all methods were the same for AM. The proposed methods were proved using laboratory prepared mixtures of the two drugs and were successively applied for their analysis in tablet form.
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