Voltammetric and amperometric behaviour of uric acid at bare and surface-modified screen-printed electrodes: studies towards a disposable uric acid sensor

Abstract

Systematic voltammetric and amperometric studies have been undertaken to examine the electrochemical behaviour of uric acid at bare and surface-modified screen-printed electrodes. The precision of the electrode manufacture was determined by cyclic voltammetry with a 1.0 × 10^–4 mol dm^–3 uric acid solution and was calculated to be 6.0%(n= 5). Several strategies were investigated in an attempt to eliminate interference from ascorbic acid. These involved coating the electrode surface with Nafion, or the enzyme L-ascorbic acid oxidase. The latter was immobilized using one of two methods: either by a simple adsorption process, or by cross-linking with bovine serum albumin and glutaraldehyde. The amperometric response at the surface-adsorbed enzyme electrode for uric acid was linear over the concentration range from 5.08 × 10^–6 to 1.51 × 10^–4 mol dm^–3; the limit of detection was 2.54 × 10^–6 mol dm^–3 using a full-scale deflection of 0.5 µA. This modified electrode exhibited no response to ascorbic acid at levels up to 0.53 mmol dm^–3. The electrode modified by cross-linking the enzyme to the surface showed no response to ascorbic acid concentrations of up to 0.093 mmol dm^–3.