Development of a thermally synthesized Co3O4 nanoparticle-based electrochemical sensor for synephrine detection in sports supplements

This study presents the development of an enhanced electrochemical sensing platform utilizing thermally synthesized Co₃O₄ nanoparticles for synephrine quantification in sports supplements. The nanoparticles, characterized by XRD, SEM, FTIR, and XPS, exhibited a well-defined cubic spinel structure with particle sizes ranging from 30–50 nm. XRD confirmed the material's crystallinity and structure, while SEM revealed quasi-spherical morphology and uniform particle distribution. FTIR identified Co–O stretching vibrations, validating the spinel framework, and XPS provided insights into cobalt oxidation states (Co²⁺/Co³⁺) and lattice oxygen. The modified electrode demonstrated superior electrochemical performance, with a 67 % increase in peak current response (from 85 μA to 142 μA) and improved electron transfer kinetics. Differential pulse voltammetry measurements under optimized conditions showed excellent analytical performance with two distinct linear ranges (0.1–10 μM and 10–100 μM). The method achieved high selectivity against common interferents at 100-fold excess concentrations, with minimal interference from caffeine and ephedrine at 10-fold excess. Analysis of ten commercial supplements showed synephrine recovery rates of 97.5–102.3 % with RSDs below 4.5 %. The method's stability was confirmed through intra-day (RSD = 2.5 %) and inter-day (RSD = 4.2 %) precision studies. This electrochemical platform aligns with current regulatory needs for accurate and reliable synephrine quantification, offering a rapid and cost-effective alternative to traditional chromatographic techniques. Its simplicity, scalability, and potential for integration into portable or automated systems highlight its promise for commercialization and routine quality control in the sports supplement industry. Future improvements could focus on further miniaturization and full automation to enhance its applicability in field settings.