An alumina-modified glassy carbon electrode: a robust platform for accurate nimodipine detection in pharmaceutical applications†

Abstract

Nimodipine (NMP) is a calcium channel blocker known for maintaining blood perfusion, particularly in the brain. Given its importance and widespread applicability, tracking NMP during industrial processes for both pharmaceutical dosage forms and raw material samples is crucial. This article discusses the use of a glassy carbon electrode (GCE) polished with commercial alumina for NMP determination. Atomic force microscopy (AFM) confirmed the presence of residual alumina on the surface of the GCE, and electrochemically active surface area (EASA) analysis demonstrated an enhancement in the active area. The alumina-polished electrode (GCE/AP) exhibited a superior response for NMP, with voltammograms obtained via differential pulse voltammetry (DPV). In this investigation, we employed density functional theory (DFT) calculations to examine the electrochemical characteristics of NMP from a theoretical standpoint. The geometry was optimized by employing the Generalized Gradient Approximation (GGA) functional, BP86, in conjunction with the Def2-TZVPPPD basis set and D3BJ dispersion corrections. To identify potential sites for oxidation and reduction, Fukui indices and dual descriptors were employed. The results indicate that the nitro group is the most probable site for reduction, whereas the dihydropyridine ring displays a proclivity for electrophilic attack. Regarding electroanalysis, two calibration curves were established through consecutive additions of NMP, with linear ranges of 0.20 to 49.0 μmol L⁻¹ and 2.92 to 13.5 μmol L⁻¹, respectively. The theoretical limits of detection (LOD) and quantification (LOQ) were, respectively, 0.06 μmol L⁻¹ and 0.20 μmol L⁻¹ for the first curve, and 4.0 μmol L⁻¹ and 12.0 μmol L⁻¹ for the second curve. Common constituents in pharmaceutical tablets were tested as potential interferents, and GCE/AP showed acceptable anti-interference ability. NMP was successfully quantified in tablet and raw material samples using the novel electrochemical method and High-Performance Liquid Chromatography (HPLC). Statistical analysis revealed no significant differences between the results. This confirms that the GCE/AP sensor was effectively applied to pharmaceutical samples, consistent with findings reported in the literature.