Sustainable electrochemical detection of benoxinate using MnO₂/MWCNT carbon paste electrode

A green electrochemical sensor utilizing pomegranate-peel-derived δ-MnO₂ nanoparticles combined with multiwalled carbon nanotubes was created as a carbon paste electrode (δ-MnO₂/MWCNTs/CPE) for the precise detection of benoxinate (BNX) in ophthalmic formulations. Cyclic voltammetry demonstrated that the modified electrode displayed the greatest electroactive surface area among the evaluated compositions, resulting in a significant improvement in BNX oxidation. An improved electrode formulation including 1.5% (w/w) MWCNTs and 1.5% (w/w) birnessite (δ-MnO₂) attained peak current responsiveness and analytical sensitivity. Under optimal conditions, the anodic peak current exhibited remarkable linearity with BNX content (r² = 0.999), whereas kinetic analyses indicated a diffusion-controlled electro-oxidation process. The sensor demonstrated remarkable selectivity, with signal changes of less than ± 2% in the presence of typical tear electrolytes, thus proving minimal interference. The suggested approach has elevated sensitivity and precision, featuring a low detection limit of 2.1 × 10⁻⁸ M and a quantification limit of 6.3 × 10⁻⁸ M. Due to its eco-friendly synthesis, durability, and analytical efficacy, the δ-MnO₂/MWCNTs/CPE platform is very appropriate for the trace-level measurement of BNX in standard pharmaceutical analysis.