A Two-Step Electropolymerization Strategy to Construct an Electrochemical Sensor for Sensitive Detection of Illegal Addition of Betamethasone in Cosmetics

A two-step electropolymerization strategy was constructed to establish an electrochemical sensor method for sensitive and selective detection of betamethasone. First, a poly-(2-aminoterephthalic acid) (P(ATA)) layer, which can significantly enhance electronic conductivity, was synthesized on the surface of the bare electrode using electropolymerization. Subsequently, taurine (Tau), which is rich in sulphonate groups, was electropolymerized and introduced into the P(ATA) layer to obtain P(Tau)/P(ATA)/GCE. Then, the electropolymerization parameters and test conditions were optimized, including the concentration of polymerization solution, the scanning rate, the polymerization cycles, buffer pH and accumulation time. Characterization of the obtained electrodes done using scanning electron microscopy and several electrochemical characterization methods proved the successful preparation of the P(Tau)/P(ATA)/GCE. Electrochemical tests of betamethasone at different concentrations (0.2–25 μg·ml −1 ) under optimal measurement conditions exhibited excellent linearity, good sensitivity. Compared with commonly employed HPLC method, the proposed sensor method was much fast, simple, environmentally friendly, and cost-effective. Compared with other sensor methods, P(Tau)/P(ATA)/GCE sensor exhibited good sensitivity and excellent stability. Moreover, the P(Tau)/P(ATA)/GCE sensor was successfully applied to quantitatively detect betamethasone in cosmetics, which provides a new method for the monitoring of illegal addition of glucocorticoids in cosmetics.