One-step electrosynthesis of poly(3,4-ethylenedioxy-thiophene)-ethylsulfate matrix for fabricating vitamin C electrochemical biosensor and its determination in commercial juices.

A stable and specific electrochemical biosensor based on a poly(3,4-ethylenedioxythiophene)-ethyl sulfate (PEDOT-EtSO) matrix with high conductivity and stability was easily fabricated. 1-Ethyl-3-methylimidazolium ethyl sulfate ([Emim][EtSO]), a halogen-free and relatively hydrolysis-stable hydrophilic ionic liquid, was selected as the supporting electrolyte for the one-step electrosynthesis of the PEDOT-EtSO matrix under the optimum conditions. The PEDOT-EtSO matrix electrosynthesized in the [Emim][EtSO] aqueous solution displayed high conductivity and stability. Inspired by preceding studies, the electrochemical biosensor based on the resulting PEDOT-EtSO matrix was facilely developed to determine the vitamin C (VC) level in commercial juices. Ascorbate oxidase (AO) was dip-coated on the surface of the as-prepared matrix, then Nafion was covered on the surface of AO layers for preventing the leakage of enzyme molecules. The fabricated biosensor displayed an excellent bioelectrocatalytic activity to the oxidation of VC. Under optimal conditions, the fabricated amperometric biosensor showed rapid response (less than 2 s) to VC at a low potential of 0.2 V over a wide range of concentrations from 8.0 × 10 to 1 × 10 M with a high sensitivity of 104.8 mA M cm, and the limit of detection and the limit of quantification of presented method was 0.147 μM and 0.487 μM, respectively. Moreover, the bioaffinity, specificity, stability, and reproducibility of the biosensor were also evaluated. Finally, the biosensor was employed to determine the content of VC in commercial juice samples by amperometric and voltammetric methods. The satisfactory results indicated that the as-prepared conducting PEDOT-EtSO films as immobilization matrix of biologically active species could be a promising candidate for the design and application of biosensors. [ABSTRACT FROM AUTHOR]