Stability-Indicating Greener UV Spectrophotometric Method for Felodipine Assay in Pharmaceutical and Urine Samples and Comprehensive Degradation Studies with IR Spectral Analysis

A stability-indicating greener UV spectrophotometric method was developed and is here reported to quantify felodipine (FDP) in pharmaceutical and spiked human urine samples, with degradation studies and IR spectral analysis of degradation products. The approach involved the preparation of calibration curves using varying concentrations of FDP in 1:1.5 acetic acid (HOAc) and measuring absorbance at 365 nm. Relative standard deviation (RSD) values for the synthetic mixture were less than 5%, and the recovery rate of FDP ranged from 95.65 to 103.1%. The FDP showed considerable degradation under basic conditions, as indicated by a shift in the λ_max, a decrease in recovery at the analytical wavelength, and changes observed in the IR spectrum. The method's robustness and ruggedness were confirmed through variations in experimental conditions and reproducibility tests, with RSD values between 3 and 5%. In the analysis of spiked human urine samples, the method demonstrated high recovery rates of FDP, ranging from 95.50 to 102.30%, with RSD values below 5%, confirming its applicability to analyse physiological samples. The me thod showed excellent linearity over 2.5–100 μg/mL FDP, low limits of detection (0.86 μg/mL), and quantification (2.62 μg/mL), with the regression coefficient (r) of 0.9983, making it suitable for routine analysis of FDP in pharmaceutical formulations and clinical samples. This method provides a reliable approach to quantify FDP, with a proven stability-indicating capability, and applies to both pharmaceutical and physiological contexts. The developed method is environmentally friendly, utilizing less toxic reagents like HOAc, minimizing waste and requiring no sophisticated equipment, making it a sustainable option for routine analysis.