Eco-friendly electrochemical sensing: An ultra-sensitive voltammetric analysis of ciprofloxacin in human serum, cow's milk and pharmaceutical samples using a glassy carbon electrode modified with poly(Na2[Cu(HR)4])

Abstract

Recent advances in electrochemistry and electrode surface modification highlight the potential of transition metal coordination compounds as effective modifiers. This study presents sodium tetraresorcinolatocuprate(II) (Na₂[Cu(HR)₄]), a newly synthesized compound characterized using UV–Vis, FT-IR spectroscopy, ICP OES, and melting point analysis. A poly(Na₂[Cu(HR)₄])/GCE was fabricated via potentiodynamic techniques, with cyclic voltammetry and electrochemical impedance spectroscopy confirming the formation of a polymer film that enhanced the electrode's active area and electrocatalytic properties. The developed poly(Na₂[Cu(HR)₄])/GCE was applied for determination of ciprofloxacin (CPF), an antibiotic prone to resistance issues, that requires reliable monitoring in pharmaceutical and biological samples. The poly(Na₂[Cu(HR)₄]) modifier significantly improved CPF detection by reducing its oxidation potential and increasing current response by eightfold compared to unmodified electrodes, suggesting the modifier's catalytic role in CPF oxidation. Differential pulse voltammetry (DPV) showed a linear CPF response over concentrations of 1.0 × 10⁻⁸ to 4.0 × 10⁻⁴ M, with detection and quantification limits of 2.0 nM and 6.8 nM, respectively. Analysis of commercial CPF brands showed 98.05–100.00 % accuracy, while spike recovery rates (99.25–100.40 %) and low interference errors (<4.6 %) validated the developed method for complex samples. The presented method is generally useful for determination of electroactive species in real complex samples and may aid in the design of more efficient electrochemical sensors.