Inhibitive determination of Hg2+ ion by an amperometric urea biosensor using poly(vinylferrocenium) film

A new approach based on amperometric urea biosensor for the inhibitive determination of Hg2+ ion using immobilized urease in poly(vinylferrocenium) film was developed. A PVF+ClO4− film was coated on Pt electrode at +0.7 V versus an Ag/AgCl by electrooxidation of poly(vinylferrocene) in metylene chloride containing 0.1 M tetrabutylammonium perchlorate (TBAP). The enzyme modified electrode PVF+E− was prepared by anion-exchange in an enzyme solution in 50 mM phosphate buffer at pH 7.0. The catalytic oxidation current at +0.7 V (versus SCE) was monitored as a response of this immobilized enzyme electrode. The response of the urease enzyme electrode was effected by the presence of metal ions in the solution. Hg2+ ion was found to be the most dominant interfering species. The presence of Hg2+ ions in the samples inhibited the urease activity, resulting a decrease in oxidation current. The amperometric urease inhibition biosensor developed in this study provided linearity to Hg2+ ions in the 2.5 μg mL−1 (9.2 × 10−6 M) to 115 μg mL−1 (4.2 × 10−4 M) concentration range. The detection limit under the optimum working conditions was determined as 2.0 μg mL−1 (7.4 × 10−6 M) for Hg2+ ion. The recovery of the biosensor was studied. Application of the biosensor to battery samples gave reliable results when compared to atomic absorption spectrometric findings. The interference effect of Cu2+, Fe3+, Cr3+, Cd2+, Zn2+, and Pb2+ ions were also investigated under the same working conditions.