A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective, with low detection limits and allowing fast analyses. This review presents the major contribution of the French scientific academic community in the field of electrochemical sensors and electroanalytical methods within the last 20 years. From the well-known polarography to the up-to-date generation of functionalized interfaces, the different strategies dedicated to analytical performances improvement are exposed: stripping voltammetry, solid mercury-free electrode, ion selective sensor, carbon based materials, chemically modified electrodes, nano-structured surfaces. The paper particularly emphasizes their advantages and limits face to the last Water Frame Directive devoted to the Environmental Quality Standards for heavy metals. Recent trends on trace metal speciation as well as on automatic “on line” monitoring devices are also evoked.

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Electrochemical sensors and devices for heavy metals assay in water: the French groups' contribution

A novel electrochemical sensor based on calixarene functionalized reduced graphene oxide: Application to simultaneous determination of Fe(III), Cd(II) and Pb(II) ions.

Papers dealing with modified electrodes made of carbon materials and composites for use in stripping voltammetry of metals have been reviewed The review consists of two parts, of which the first considers applications of modified glassy carbon and carbon paste electrodes, while the second describes diverse modified carbon-containing composite and microscopic electrodes Information about modifiers, electrode modification methods, conditions, and limits of detection of elements in different materials has been tabulated The review covers 550 papers published in Russia and abroad between 1990 and the first half of 2007

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Modified carbon-containing electrodes in stripping voltammetry of metals

Solid-state pH ultramicrosensor based on a tungstic oxide film fabricated on a tungsten nanoelectrode and its application to the study of endothelial cells

Oxygen demands: COD- Biochemical Oxygen Demand BOD- Total organic carbon - TOC- Dissolved oxygen- pH Measurements- Metals- Non-Metal Inorganic Ions and Molecules- Electroanalysis and Speciation- Nanoparticles-emerging contaminants- Pharmaceuticals and Personal Care Products- Surfactants- Aromatic Hydrocarbons and their Derivatives- Nitrated Compounds: Explosives- Pesticides- Volatile organic compounds- Sulphur Compounds (H2S, S-oxides)- Ammonia and Nitrogen Oxides- Carbon Oxides

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Environmental analysis by electrochemical sensors and biosensors

Nafion coated glassy carbon electrodes (NCE) are employed for preconcentrating and detecting Fe2+ and Fe3+ cations from aqueous solutions. The influence of the supporting electrolyte composition and of the redox state on the analyte partitioning within the Nafion coating are examined. By using cyclic voltammetry, the ion-exchange voltammetric determination of iron in the μM concentration range is achieved from voltammetric peak currents relevant to the reversible redox process: Fe3++e⇋Fe2+. Depending on the starting potential of the voltammetric scan, all the iron is initially converted to the Fe(III) or Fe(II) redox state, so that, from the voltammogram, the overall concentration of iron is always obtained. However, the simple measurement of the open circuit potential at the NCE before starting the scan allows one to get information on the ratio between Fe(III) and Fe(II) incorporated in the Nafion coating. From relevant ion-exchange distribution coefficients, open circuit potential values can be related to the Fe(III)/Fe(II) concentration ratio in the sample. The use at the NCE of a new electroanalytical technique named multiple square-wave voltammetry in the double differential mode allows the significative lowering of detection limits pushing the operative range of the method in the nM range. Application to analysis of Fe(II) in the pore-waters of sediments of the lagoon of Venice (Italy) is presented.

E. Birriel

Papers

Trace Iron Determination by Cyclic and Multiple Square-Wave Voltammetry at Nafion Coated Electrodes. Applicationto Pore-Water Analysis