Pioneering spectrophotometric analysis of cilnidipine via coupling with amino reagents: application to pharmaceuticals and biological fluids

Cilnidipine is an important antihypertensive medication within the dihydropyridine class of calcium channel blockers. The precise quantification of cilnidipine concentrations in pharmaceutical formulations and biological fluid samples is crucial for ensuring therapeutic efficacy and safety. Traditional analytical techniques for measuring cilnidipine amounts have included various methods, with oxidative coupling reactions proving particularly effective. This study presents a novel spectrophotometric method for cilnidipine quantification, employing oxidative coupling with 4-aminoAntipyrine and 4-amino diphenylamine. These reactions yield colored compounds that can be detected in the visible spectrum at wavelengths of 528 nm and 721 nm, significantly improving both sensitivity and accuracy. Methods A and B adhere to Beer's law across specified concentration ranges of 1–55 and 1–30 µg/mL, respectively, demonstrating high molar absorptivity of 1.098×10⁴ L/(mol⋅cm) for method A and 2.1179×10⁴ L/(mol⋅cm) for method B, which highlights their analytical robustness. The limit of detections (LOD) was estimation and found to be 0.1159 and 0.3865 µg/mL for methods A and B, correspondingly, while the limit of quantifications (LOQ) was 0.1976 (method A) and 0.5848 µg/mL (method B), showcasing their strong analytical performance. A thorough validation of linearity and precision was performed, with Sandell's sensitivity assessed at 0.04486 µg/cm² for method A and 0.02325 µg/cm² for method B. This innovative approach provides researchers and healthcare professionals with a reliable tool for accurate cilnidipine measurement, thereby enhancing treatment outcomes and ensuring high standards of pharmaceutical quality. The two suggested techniques effectively determined Cilnidipine; with a decent average recovery in pharmaceutical tablets 99.53%–100.2 % and in human urine and serum samples of 99.77%–100.58 %, no intrusions of co-existing additives present in commercial dosage forms were noted.