Adsorptive stripping voltammetric behaviour of colloidal gold and immunogold on carbon paste electrode

Abstract

A new adsorptive stripping voltammetric method (ASV) for the determination of colloidal gold is investigated. The method also allows the measurement of the average diameter of the particle size and it is based on the previous metal accumulation onto a carbon paste surface electrode followed by an oxidation process of the adsorved colloid to an Au(III)-chloro complex which is then electrochemically reduced to Au(0). Using differential pulse voltammetry (DPV), a linear calibration range of concentrations between 5.08 × 10⁻⁸ and 4.06 × 10⁻⁶ M can be covered and a detection limit of 1.78 × 10⁻⁸ M (S/N = 3) was found. When a goat anti-human IgG is labelled with colloidal gold, the differential pulse adsorptive stripping voltammetric method (DPASV) allows the determination of antibodies in a range of concentrations from 2.77 × 10⁻⁸ to 1.86 × 10⁻⁸ M (relative standard deviation = 5%). The proposed method seems to be an excellent analytical approach for the determination of any protein or macromolecule which can be labelled with microparticles of colloidal gold and offers a potential new path to immunoelectroanalytical assay.