Hari Gunasingham

Carbon paste-tetrathiafulvalene amperometric enzyme electrode for the determination of glucose in flowing systems

The development of a carbon paste-tetrathiafulvalene amperometric enzyme electrode for the determination of glucose in flowing streams is described. The enzyme electrode is operated in a flow-through detector based on the wall-jet configuration under flow injection (FI) and steady-state (SS) conditions. Under FI conditions, high precision (0.6%) and sample throughput (120 samples h-1) are possible. Moreover no pre-conditioning of the electrode is required. The flow system is suitable for the determination of glucose in whole blood without sample dilution. With proper orientation of the jet with respect to the enzyme electrode, high accuracy can be obtained under SS conditions.

Platinum-dispersed Nafion film modified glassy carbon as an electrocatalytic surface for an amperometric glucose enzyme electrode

A Nafion film dispersed with platinum particles formed on a glassy carbon electrode combines the electrocatalytic activity of platinum with the background stability of glassy carbon. It serves as a selective and sensitive electrode surface for an amperometric glucose enzyme electrode. Details on the construction and the functional characteristics of the enzyme electrode are described. It is shown that the electrode is well suited to the determination of levels of glucose in blood by flow injection with amperometric detection.

Comparative study of glassy carbon as an electrode material

There have often been contradications reported in regard to the efficacy of glassy carbon in voltammetric applications. The problem stems from the fact that there are a large variety of carbons available from various manufacturers that vary in their bulk structure, particularly in the degree of compactness. The extent of compactness affects both the bulk and surface properties of glassy carbon. The latter has a bearing on the formation of surface carbon-oxygen functionalities, which influence the electrochemical response of the carbon.

Use of electrochemical detection in normal-phase high performance liquid chromatography

Abstract The application of electrochemical detection to normal-phase liquid chromatography (using non-aqueous eluents of low dielectric constant) holds considerable potential for the determination of a number of important organic compounds. By choosing an appropriate supporting electrolyte and a modified reference electrode, high sensitivity and a large potential working range is attainable. The efficacy of electrochemical detection in normal-phase liquid chromatography is demonstrated in its application to the determination of phenols.

Anodic stripping voltammetry of lead, cadmium and zinc in the presence of copper with an ion-exchange column

The determination of lead, cadmium and zinc by anodic stripping voltammetry is made difficult by the presence of large amounts of copper. For lead, ordinarily, 0.10 mg l–1 of lead is totally suppressed by the presence of 100 mg l–1 of copper (molar ratio of copper to lead = 3261.5) owing to the very high background currents brought about by undissolved copper atoms. For zinc and cadmium, intermetallic compound formation occurs, which affects the stripping peak currents of both metals. In this work, on-line ion-exchange separation was used prior to differential-pulse anodic stripping voltammetry (DPASV) for the determination of lead, zinc and cadmium in the presence of excess of copper. A commercially available resin, Dowex XFS 43084, allowed suppression of the copper stripping peak. An additional use of the ion-exchange column is to extend the useful range of DPASV for the determination of copper to the millimolar range.

Effect of pH on the response of glassy carbon electrodes

The use of glassy carbon as an electrode material engenders a number of practical problems owing to the presence of C—O functionalities on its surface. One such problem is the susceptibility of the electrode to pH changes. Highly surface-active glassy carbon electrodes having a high proportion of irreversible C—O groups are particularly prone to variations in pH compared with ones having mainly quinoidal species. This is reflected in the performance of glassy carbon in the cyclic voltammetry of hydroquinone.

Medium effects in the stripping voltammetry of mercury

The effect of the stripping medium on the stripping voltammetry of monolayer mercury films has been studied using a wall-jet electrode in conjunction with flow injection. A suitable methodology is proposed which allows the obviation of adsorption effects in the determination of trace levels of mercury. This approach can be used in routine analysis.

Anodic stripping voltammetry with a Triton X-100 modified mercury film electrode using flow injection

The effect of Triton X-100 on anodic stripping voltammetry at a mercury film electrode (MFE) depends on the concentration of the Triton X-100 solution. At concentrations below the critical micellization concentration (c.m.c.), the effect that is seen is a decline in the stripping peak current and corresponding decline in sensitivity. This is due to the adsorption of surfactant on the MFE surface. At Triton X-100 concentrations above the c.m.c., however, the deactivation of the electrode is reversed and enhanced sensitivity and lower background currents are obtained. This work suggests the use of surfactants to modify advantageously electrode surfaces.