Construction and evaluation of carbon black and poly(ethylene co-vinyl)acetate (EVA) composite electrodes for development of electrochemical (bio)sensors

- Carbon black (CB) and poly(ethylene co-vinyl)acetate (EVA) as new composite electrode.
- EVA/CB rigid composite electrode with high robustness and very good electroanalytical properties.
- Electrochemical sensor with high electron-transfer rate constant for hexacyanoferrate(III)/(II) and wide useful potential window.
- A simple and alternative composite which can be a useful for preparation of wearable electrodes in the future.

The preparation of a new carbon composite electrode based on a mixture of poly(ethylene-co-vinyl acetate) (EVA) and carbon black (CB) is described. The resulting EVA/CB electrode combines the excellent electrochemical properties of CB with the advantages brought by the EVA polymer, which allows the preparation of very rigid composite electrodes. The composition of the composite was optimized, that based on 25EVA:75CB (w/w) leading to electrodes with the best performance. The composite electrodes were characterized by surface analysis techniques and by cyclic voltammetry and were applied in different electroanalytical systems. The EVA/CB electrode was employed in a flow injection analysis system as an amperometric detector for ascorbic acid showing a linear dynamic range from 5.0 × 10−5 mol L−1 to 1.0 × 10−3 mol L−1 with 63 injections per hour. Prussian Blue (PB) films were prepared on the composite electrode surface and the resulting modified electrode was successfully used for the amperometric determination of hydrogen peroxide. Determination of hydrogen peroxide present in pharmaceutical samples was realized using the proposed methodology and official method and the results found are in agreement at the 95% confidence level. The EVA/CB/PB electrode was also used for the preparation of a glucose biosensor, by immobilizing the enzyme glucose oxidase (GOx) on top, EVA/CB/PB-GOx, with a linear range from 9.99 × 10−5 mol L−1 to 6.95 × 10−4 mol L−1. The proposed composite electrode exhibits favorable features such as high mechanical resistance, low cost, simple preparation, and ease of chemical modification, being versatile for a variety of electroanalytical applications. The results show an excellent combination of good electrode kinetics with small background current and reproducible response.