Derivative- Ratio Spectrophotometric, Chemometric and HPLC Validated methods for Simultaneous Determination of Amlodipine and Atorvastatin in Combined Dosage Form

Three methods were developed for simultaneous determination of amlodipine and atorvastatin without previous separation. The first method depends on first derivative of the ratios spectra by measurements of the amplitudes at 228 and 245 nm for amlodipine using 25 ?g/mL of atorvastatin as a divisor and at 284 and 295 nm for atorvastatin using 80 ?g/mL of amlodipine as a divisor. Calibration graphs were established in the range of 10-100 ?g/mL and 2.5-30 ?g/mL for amlodipine and atorvastatin, 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 (HPLC), separation was performed by using C18 reversed phase column and a mobile phase of acetonitrile: 0.05 M KH2PO4 (60:40v/v) adjusted by phosphoric acid to pH 3.5 at flow rate of 1 mL/min. All proposed methods were extensively validated and the results obtained by adopting the three methods were statistically analyzed and compared with those obtained from a reported method.