# Spectroscopic methods for the simultaneous determination of amlodipine besylate and Hydrochlorothiazide in their binary mixture and pharmaceutical dosage form

## TL;DR

This paper introduces eco-friendly spectrophotometric methods to accurately measure two drugs in mixtures and pharmaceutical products.

## Contribution

The study proposes green analytical methods for determining amlodipine besylate and hydrochlorothiazide in mixtures.

## Key findings

- A selective method at 366 nm determines amlodipine besylate without interference from hydrochlorothiazide.
- Five green spectrophotometric approaches were validated for hydrochlorothiazide with low detection limits.
- All methods were environmentally assessed using tools like the Analytical GREEnness Calculator.

## Abstract

The development of environmentally friendly analytical methods is important in the current scientific landscape. This study presents an investigation into several green spectrophotometric methods for the determination of amlodipine besylate and hydrochlorothiazide in both their pure binary mixtures and pharmaceutical formulations. A spectrophotometric method is proposed for the selective determination of amlodipine besylate in the presence of hydrochlorothiazide at 366 nm, where no interference from hydrochlorothiazide was observed. Additionally, a novel five different spectrophotometric approaches were applied for the determination of hydrochlorothiazide: the dual wavelength method, first derivative method, ratio difference method, and ratio derivative method, as well as Fourier Self-Deconvolution method. Amlodipine besylate’s linearity range was 5–30 µg/mL, whereas hydrochlorothiazide’s was 3–18 µg/mL reaching limits of detection of 1.238, 0.906, 0.825, 0.540, 0.779 and 0.805 µg/mL, respectively for all the proposed methods. The proposed methods were validated in accordance with ICH international guidelines, including full statistical analysis and comprehensive environmental evaluation using multiple assessment tools as The Analytical GREEnness Calculator, the Modified Green Analytic Procedure Index, spider diagram, and green analytical selection tool.

The online version contains supplementary material available at 10.1038/s41598-025-33191-4.