Sensitive amperometric determination of methimazole based on the electrocatalytic effect of rutin/Multi-walled carbon nanotube film

Electrochemical deposition was used to prepare a glassy carbon electrode modified with multi-walled carbon nanotubes and the glycosidic compound, rutin (R/MWCNTs/GCE). Cyclic voltammetry of the modified electrode in aqueous solution (pH 8) showed a pair of well-defined, stable and reversible redox peaks with surface confined characteristics. The catechol moiety of rutin produced the voltammetric peaks via a 2 electron, 2 proton mechanism in the range of 0.0-0.4 V (vs. Ag/AgCl). The transfer coefficient (alpha), heterogeneous electron transfer rate constant (k(s)), and surface concentration (Gamma) for R/MWCNTs/GCE were calculated by using the cyclic voltammetric data. The modified electrode showed excellent catalytic activity toward oxidation of methimazole. Fixed-potential amperometry was used for sub-micromolar determination of methimazole at pH 8. Linear dependence of anodic current to methimazole concentration was obtained in the range of 0.1-26 mu M of the drug with a limit of detection at 18 nM. The modified electrode retained its initial response for at least 2 weeks if stored in dry ambient conditions. The electrode was used for the amperometric determination of methimazole in formulations and spiked blood serum samples, successfully. (C) 2014 Elsevier B.V. All rights reserved.