Development of a Green Spectrophotometric Method for the Determination of Amlodipine Besylate Using Ion-Pair Formation with Alizarin Red S and Its Application in Pharmaceutical Formulations

Abstract

The aim of the presented work was to introduce simple, fast and sensitive spectroscopic technique for the determination of amlodipine besylate in bulk and dosage forms using UV-visible spectrophotometer based on formation of an ion-pair association with Alizarin Red S. The new absorption band at 570 nm was found for the formed complex. Results revealed that the recommended conditions were achieved at a concentration of dye 10 µg/mL, temperature 20–25 °C and stability of complexes up to 60 min. The results showed that maximum absorbance was obtained at pH = 5.52 without adding any acid or base and Job's method of mixture indicated that there was 1:1 ratio of amlodipine and dye. Linear calibration graph was obtained over the concentration range of 2.5–20 µg/mL with apparent molar absorptivity of 22511.89 L·mol⁻¹·cm⁻¹ and Sandell index of 0.02518 µg/cm². Accuracy, precision and reproducibility were also satisfactory and determined low concentrations. LOD was found to be 0.1261 µg/mL and LOQ was calculated as 0.3821 µg/mL. The applicability of the described method was checked with the commercial tablet formulation Amlopine. Method showed green chemistry index as 0.78 which is attributed to the usage of distilled water and minimized organic solvents and waste products. Proposed method can be successfully applied for determination of amlodipine in raw materials and pharmaceutical dosage forms.