Analytical Sciences

Direct Electrochemistry of Hemoglobin Immobilized on Hydrophilic Ionic Liquid-chitosan-ZrO₂ Nanoparticles Composite Film with Carbon Ionic Liquid Electrode as the Platform

Lifang QIAO, Ruifang GAO, and Jianbin ZHENG

Institute of Analytical Science, Shaanxi Provincial Key Laboratory of Electroanalytical Chemistry, Northwest University, Xi’an, Shaanxi 710069, P. R. China

A stable composite film composed of 1-butyl-3-methyl-imidazolium tetrafluoroborate, chitosan, zirconia nanoparticles and the hemoglobin (Hb) was cast on the surface of an ionic liquid of an N-butylpyridinium hexafluorophosphate modified carbon paste electrode to fabricate a modified electrode. Scanning electron microscopy images of the modified electrode indicated that there was a dendritic structure on the modified electrode, and UV-Vis and FT-IR spectra showed that Hb in the composite film retained its native structure. Voltammetric experiments at the modified electrode showed that, in a pH 7.0 phosphate buffer solution, a pair of well-defined and quasi-reversible redox voltammetric peaks was obtained with the formal potential located at −0.216 V. The electrochemical parameters of Hb in the composite film were further carefully calculated: the electron-transfer rate constant was 0.52 s⁻¹ and the charge transfer coefficient was 0.34. The catalytic reduction peak current had a linear relationship with the concentration of trichloroacetic acid (TCA) in the range from 0.2 to 10.3 mmol/L with a detection limit of 66.7 μmol/L. Therefore, the composite film as a novel matrix opened up a possibility for further study on the design of enzymatic biosensors with potential applications.

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