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 .O x 10-4 rnol 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 surfaceadsorbed enzyme electrode for uric acid was linear over the concentration range from 5.08 x 10-6 to 1.51 x 10-4 rnol dm-3; the limit of detection was 2.54 x 10-6 rnol dm-3 using a full-scale deflection of 0.5 pA. This modified electrode exhibited no response to ascorbic acid at levels up t o 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.

Electrocatalytic oxidations of biological molecules (ascorbic acid and uric acids) at highly oxidized electrodes

“…A major obstacle in monitoring this compound is interferences from other electroactive constituents, such as ascorbic acid (AA), which oxidizes close to the potential of UA on various types of electrodes [2,[5][6][7]. Several electrochemical procedures for UA detection are based on oxidation at electrodes modified with polymers [2,4,8], enzymes [9,10] and dye-doped sol-gel layers [6], etc. These voltammetric techniques are more selective, less costly, and less time-consuming than those based on colorimetry or spectrophotometry [11].…”

Selective Determination of Uric Acid by Using a β-Cyclodextrin Modified Electrode

“…However, a major problem encountered frequently in the detection of UA is the interference of ascorbic acid (H 2 A), which can be oxidized at a potential close to that of UA [4]. Various methods such as the adsorption=medium exchange approach [5], enzyme-based techniques [6][7][8][9], the use of polymer-modified electrodes [10][11][12], the use of electrochemically pretreated carbon paste electrodes [13] or Nafion-coated glassy carbon electrodes [14], have been developed for the selective determination of UA. These voltammetric techniques are more selective, less costly and less time-consuming than those based on colorimetry or spectrophotometry [15].…”

Electrochemical Detection of Uric Acid in Mixed and Clinical Samples: A Review

“…A reliable, simple, cheap, and precise disposable test strip for detecting UA in whole blood or other physiological fluids could be useful as an alternative to the assays currently employed. So far there appears to be only limited work reported for the direct detection of UA in human whole blood with disposable electrodes [31,[64][65][66][67][68][69]. For example a recent development involving the use of ferricyanide as an electron-transfer mediator has been developed.…”

“…Electrochemical sensors have attracted much attention due to their advantages of short analysis times, simple experimental procedures which can be applied to a variety of physiological samples and relatively cheaper instrumental requirements along with high selectivity and sensitivity [30]. As UA can easily be oxidised at common electrodes in aqueous solutions to give allantoin as the major product, its electrochemical nonenzymatic approach seems to be one method of choice [31][32][33][34][35][36]. Uric acid (UA) and ascorbic acid (AA) are present in biological fluids such as blood and urine.…”