SnO2: A comprehensive review on structures and gas sensors

This article reviews the electrochemistry and electroanalytical applications of carbon paste-based electrodes, sensors, and detectors on the occasion of the half-of-century anniversary since the discovery of carbon paste. The review (with 333 references) has been prepared in the form of a retrospective compilation presenting the field by means of various facts, notes, data, surveys, and summaries, including numerous rarities or curiosities that illustrate the individual achievements and milestones. Carbon paste-based electrodes are discussed in their entirety by covering all important areas of the field, starting from basic characterization of carbon paste as the electrode material, via its typical physicochemical and electrochemical properties or specific features, up to a representative documentation of their applicability in electrochemical and electroanalytical measurements.

Carbon Paste Electrodes in Facts, Numbers, and Notes: A Review on the Occasion of the 50‐Years Jubilee of Carbon Paste in Electrochemistry and Electroanalysis

A review is presented dealing with the use of carbon paste as an electrode maaterial for electrochemical sensors (311 references). It covers mainly publications which appeared during the period 1990–1993; numerous applications demonstrate the widespread applicability of carbon paste in the field of electrochemical analysis, such as voltammetry, amperometry, and potentiometry, but also as an electrode for electrochemical detectors in flow systems.

Sensors based on carbon paste in electrochemical analysis: A review with particular emphasis on the period 1990–1993

Since the discovery of perchlorate in the ground and surface waters of several western states, there has been increasing interest in the health effects resulting from chronic exposure to low (parts per billion [ppb]) levels. With this concern has come a need to investigate technologies that might be used to remediate contaminated sites or to treat contaminated water to make it safe for drinking. Possible technologies include physical separation (precipitation, anion exchange, reverse osmosis, and electrodialysis), chemical and electrochemical reduction, and biological or biochemical reduction. A fairly unique combination of chemical and physical properties of perchlorate poses challenges to its analysis and reduction in the environment or in drinking water. The implications of these properties are discussed in terms of remediative or treatment strategies. Recent developments are also covered.

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Perchlorate Chemistry: Implications for Analysis and Remediation

Electrochemical detection of hydrogen peroxide using an edge-plane pyrolytic-graphite electrode (EPPG), a glassy carbon (GC) electrode, and a silver nanoparticle-modified GC electrode is reported. It is shown, in phosphate buffer (0.05 mol L(-1), pH 7.4), that hydrogen peroxide cannot be detected directly on either the EPPG or GC electrodes. However, reduction can be facilitated by modification of the glassy-carbon surface with nanosized silver assemblies. The optimum conditions for modification of the GC electrode with silver nanoparticles were found to be deposition for 1 min at -0.5 V vs. Ag from 5 mmol L(-1) AgNO3/0.1 mol L(-1) TBAP/MeCN, followed by stripping for 2 min at +0.5 V vs. Ag in the same solution. A wave, due to the reduction of hydrogen peroxide on the silver nanoparticles is observed at -0.68 V vs. SCE. The limit of detection for this modified nanosilver electrode was 2.0 x 10(-6) mol L(-1) for hydrogen peroxide in phosphate buffer (0.05 mol L(-1), pH 7.4) with a sensitivity which is five times higher than that observed at a silver macro-electrode. Also observed is a shoulder on the voltammetric wave corresponding to the reduction of oxygen, which is produced by silver-catalysed chemical decomposition of hydrogen peroxide to water and oxygen then oxygen reduction at the surface of the glassy-carbon electrode.

Silver nanoparticle assemblies supported on glassy-carbon electrodes for the electro-analytical detection of hydrogen peroxide.

An improved voltammetric method for the determination of trace amounts of uric acid with electrochemically pretreated carbon paste electrodes.

A carbon paste electrode modified with a liquid anion exchanger (Amberlite LA2) was used for the voltammetric determination of mercury(II). Mercury is preconcentrated, as tetrachloromercurate(II), onto the surface of the modified electrode only by the ion-exchange effect of the modifier without application of potential. After exchange of the medium the accumulated amount of mercury(II) is determined by differential pulse anodic stripping voltammetry in a blank electrolyte solution. The response depends on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 1 μg Hg(II)/l when a suitable time for preconcentration was chosen. Preconcentration for 5 min yields a linear calibration graph for concentrations up to 1000 μg Hg(II)/l. The effect of other ions on the determination of mercury and the applicability of the method to the analysis of phenylmercury compounds in pharmaceutical preparations were investigated.

Voltammetric determination of trace amounts of mercury with a carbon paste electrode modified with an anion-exchanger

Determination of traces of copper by anodic stripping voltammetry after its preconcentration via an ion-exchange route at carbon paste electrodes modified with vermiculite

A commercial indium–tin oxide (ITO) film, deposited on a glass substrate, was investigated for its potential use as a disposable amperometric sensor for hydrogen peroxide determination in aqueous solutions. After a very simple, yet crucial, electrochemical pre-treatment of a fresh ITO film electrode, a stable and sensitive electrocatalytic response to hydrogen peroxide was exhibited. The electrocatalytic character and factors influencing hydrodynamic amperometric performance of the ITO film electrode were examined and discussed. Under optimized conditions, the amperometric signal was linearly proportional to the hydrogen peroxide concentration over the range 8.4 × 10–5–2.1 × 10–3 mol l–1(2.9–71.4 mg l–1) with a detection limit of 5.6 × 10–1 mol l–5 mol l–1(1.9 mg l–1). The electrode also displayed good reproducibility with an sr value of 1.5% for 20 consecutive chronoamperometric measurements of 2.8 × 10–4 mol l–1 hydrogen peroxide.

Indium–tin oxide film electrode as catalytic amperometric sensor for hydrogen peroxide

A simple method is presented for the simultaneous differential pulse voltammetric determination of uric acid, xanthine and hypoxanthine It is based on the improved current responses of the three analytes at carbon paste electrodes polarized in a dilute alkaline medium (0002 mol/l NaOH, 01 mol/l NaClO4) at 13 V vs SCE for a short time Compared with the methods reported in the literature, this procedure has a much wider linear range (2 to 3 orders of magnitude in concentration), lower detection limits (5 to 10 μg l−1) and less interference by ascorbic acid The electrochemical responses were found to be dependent on the pre-anodization potential and the time imposed on the electrodes as well as on the alkalinity of the supporting electrolyte The proposed procedure was used to determine uric acid, xanthine and hypoxanthine in human urine without any preliminary treatment

Xiaohua Cai

Papers

An improved voltammetric method for the determination of trace amounts of uric acid with electrochemically pretreated carbon paste electrodes.

Voltammetric determination of trace amounts of mercury with a carbon paste electrode modified with an anion-exchanger

Determination of traces of copper by anodic stripping voltammetry after its preconcentration via an ion-exchange route at carbon paste electrodes modified with vermiculite

Indium–tin oxide film electrode as catalytic amperometric sensor for hydrogen peroxide

Simultaneous determination of uric acid, xanthine and hypoxanthine with an electrochemically pretreated carbon paste electrode