Simultaneous evaluation of losartan and amlodipine besylate using second-derivative synchronous spectrofluorimetric technique and liquid chromatography with time-programmed fluorimetric detection

Abstract

This study is concerned with two sensitive, fast and reproducible approaches; namely, second-derivative synchronous fluorimetry (method I) and reversed phase high-performance liquid chromatography with fluorimetric detection (method II) for synchronized evaluation of losartan (LOS) and amlodipine besylate (AML). Method I is based on measuring second-derivative synchronous fluorescence spectra of LOS and AML at Δ<i>λ</i> = 80 nm in water. The experimental factors influencing the synchronous fluorescence of the considered compounds were sensibly adjusted. The chromatographic analysis was executed on a Nucleodur MN-C18 column of dimensions; 250 × 4.6 mm i.d. and 5 µm particle size). The fluorimetric detection was time-programmed at <i>λ</i>em = 440 nm for AML (0.0-7.5 min) and at <i>λ</i>em = 400 nm for LOS (7.5-10 min) after excitation at <i>λ</i>ex = 245 nm. The mobile phase is a blend of acetonitrile with 0.02 M phosphate buffer in a proportion of 45 : 55, pH 4.0, pumped using a flow rate of 1 ml min^-1. The calibration plots were established to be 0.1-4.0 µg ml^-1 for both drugs in method I and 0.05-4.0 µg ml^-1 for both drugs in method II. The study was extended to the evaluation of the two drugs in their co-formulated tablets.