Determination of Amlodipine and Valsartan in Binary Mixture Using Derivative- Ratio Spectrophotometric, Chemometric and High Performance Liquid Chromatographic-UV Methods

Three methods were developed for simultaneous determination of amlodipine and valsartan without previous separation. The first method depends on first derivative of the ratios spectra (DD1) by measurements of the amplitudes at 234.5 and 247 nm for amlodipine using 30μg/mL of valsartan as a divisor and at 282 and 292 nm for valsartan using 80μg/mL of amlodipine as a divisor. Calibration graphs were established in the range of 10-100 μg/mL and 5-40 μg/mL for amlodipine and valsartan, respectively. The second method describes the use of multivariate spectophotometric calibration for the simultaneous determination of the analyzed binary mixture, where the resolution is accomplished by using partial least squares (PLS) regression analysis. In the third method, High performance liquid chromatography (HPLC), separation was performed by using reversed phase column and a mobile phase composed of acetonitrile: KH2PO4 (50:50v/v) adjusted to pH 3.5 by phosphoric acid. The proposed methods were validated and results obtained by adopting the three methods were statistically analyzed and compared with those obtained from compendial method.