Electrochemical characterisation of nanoparticulate zirconium dioxide-on-gold electrode for electrochemical detection in flow-based analytical systems

Abstract

The modification of gold (Au) electrode using zirconium dioxide nanoparticles (ZrO2 NPs) has been investigated for enhanced electrochemical (EC) detection in flow-based analytical systems. The average size of ZrO2 NPs deposited in a facile procedure on the Au electrode surface was calculated as 22.5 ± 7 nm. Redox behaviour of a test solute, ferrocyanide [Fe(CN)6]4-, on the bare- and ZrO2-Au electrodes was initially investigated using cyclic voltammetry. From the voltammograms of bare- and ZrO2-Au electrodes, the EC reversibility values and effective surface area were experimentally determined for the first-time in this study. Further, EC reversibility and 100% increase in effective electrode surface area were confirmed in ZrO2-Au electrode through investigating the detection response (current). The EC performance of the ZrO2-Au electrode was then investigated in amperometric detection of selected electroactive solutes separated by reversed-phase HPLC. The limits of detection (LODs), based upon an injection volume of 10 μL for ascorbic acid, 2,3-dihydroxybenzoic acid and pyrocatechol were 0.09 μM, 0.04 μM, and 0.10 μM, respectively (RSD 2.5%, n = 9, r2 = 0.99 for concentration range 1–100 μM). These LODs for the ZrO2-Au electrode were 2-times lower for 2,3-DHBA, and pyrocatechol than the lowest LODs reported in the literature for EC detection in HPLC. The ZrO2-Au electrode demonstrated satisfactory repeatability of preparation, detection reproducibility and high stability (8.5 h) during continuous-flow in FIA and 45 days during intermittent use with HPLC, at flow rate of 0.6 mL min−1. This work has demonstrated a comprehensive EC characterisation of Au electrode with nanoparticulate ZrO2 for flow-based analytical systems.