Development of an electrochemical immunosensor for sensitive detection of clenbuterol in food supplements

A label-free electrochemical immunosensor is reported for trace-level determination of clenbuterol in sports food supplements. A carboxyl-terminated 11-mercaptoundecanoic acid (11-MUA) self-assembled monolayer was assembled on a gold micro-disk and activated with EDC/NHS to covalently anchor anti-clenbuterol antibodies. Clenbuterol binding was transduced by electrochemical impedance spectroscopy, giving a linear ΔR_ct–log C relationship from 10⁻¹¹ to 10⁻⁶ g/mL (R² = 0.993) and a limit of detection of 3.2 × 10⁻¹² g/mL. The sensor exhibits excellent precision (intra-/inter-assay RSD 2.5 %/3.1 %) and selectivity against structurally related β-agonists. Recoveries of 92.5–105.8 % were obtained in spiked commercial supplements, confirming matrix tolerance. After 20 days at 4 °C the signal retained 90 % of its initial value, underscoring practical shelf-life. These figures of merit match or surpass chromatographic and ELISA benchmarks while requiring no sophisticated instrumentation or sample derivatisation. The platform therefore provides a rapid, low-cost tool for on-site clenbuterol surveillance and supports regulatory compliance in sports-nutrition manufacturing.