Anodic stripping voltammetry (ASV) is more simple than cathodic stripping voltammetry (CSV) because in principle it can be done without any reagents. The preconcentration consists of a plating step in which the metal is reduced to the metallic state which either forms an amalgam with the mercury of a mercury drop electrode, or it is plated on the surface of a solid electrode consisting of metal (gold, platinum) or another conductive material (carbon, diamond). These electrodes are conveniently made as microwires and sealed in a pipette tip, which is both convenient and gives a sensitive microelectrode with a thin diffusion layer. The gold microwire electrode does not require polishing and is cleaned electrochemically prior to each measurement. With this electrode several metals can be determined with very good sensitivity in seawater, including copper, arsenic, zinc, manganese and lead.

It is worthwhile to use these electrodes especially if you wish to determine copper or arsenic, because the sensitivity is much greater than using any other electrode. And, there are significant analytical advantages related to electrode regeneration and without the need for strong acid for arsenic. The electrochemical instrument company Metrohm is now supplying a combination electrode that includes a gold microwire in their electrode stand.

Vibrating microwire electrodes

The microwire electrodes are readily converted to vibrating electrodes by insertion of a vibrator in the top of the microwire holder. Vibration causes the diffusion layer to become thinned to better than 1 µm for a 10 µm microwire. This much improves the sensitivity of the microwire electrode.

The vibrating microwire electrodes are available from our laboratory including a vibrator unit with replaceable electrode tips and a powersupply.

Contact: vandenberg@liv.ac.uk

Look in the relevant papers for the correct procedures.

Billon, G. and C. M. G. van den Berg (2004). "Gold and silver micro-wire electrodes for trace analysis of metals." Electroanalysis 16(19): 1583-1591.

Widmann, A. and C. M. G. Van Den Berg (2005). "Mercury detection in seawater using a mercaptoacetic acid modified gold microwire electrode." Electroanalysis 17(10): 825-831.

Salaün, P. and C. M. G. van den Berg (2006). "Voltammetric detection of mercury and copper in seawater using a gold microwire electrode." Analytical Chemistry 78(14): 5052-5060.

Chapman, C. S. and C. M. G. Van Den Berg (2007). "Anodic stripping voltammetry using a vibrating electrode." Electroanalysis 19(13): 1347-1355.

Salaün, P., B. Planer-Friedrich and C. M. G. van den Berg (2007). "Inorganic arsenic speciation in water and seawater by anodic stripping voltammetry with a gold microelectrode." Analytica Chimica Acta 585(2): 312-322.

Gibbon-Walsh, K., P. Salaun and C. M. G. van den Berg (2010). "Arsenic speciation in natural waters by cathodic stripping voltammetry." Analytica Chimica Acta 662(1): 1-8.

Alves, G. M. S., J. Magalhaes, P. Salaun, C. M. G. van den Berg and H. Soares (2011). "Simultaneous electrochemical determination of arsenic, copper, lead and mercury in unpolluted fresh waters using a vibrating gold microwire electrode." Analytica Chimica Acta 703(1): 1-7.

Gibbon-Walsh, K., P. Salaun, M. K. Uroic, J. Feldmann, J. M. McArthur and C. M. G. van den Berg (2011). "Voltammetric determination of arsenic in high iron and manganese groundwaters." Talanta 85(3): 1404-1411.

Gibbon-Walsh, K., P. Salaun and C. M. G. van den Berg (2011). "Determination of manganese and zinc in coastal waters by anodic stripping voltammetry with a vibrating gold microwire electrode." Environmental Chemistry 8(5): 475-484.

Salaün, P., K. Gibbon-Walsh and C. M. G. van den Berg (2011). "Beyond the hydrogen wave: new frontier for the voltammetric detection of trace elements by stripping voltammetry." Analytical Chemistry 83(10): 3848-3856.

Gibbon-Walsh, K., P. Salaün and C. M. G. van den Berg (2012). "Determination of arsenate in natural pH seawater using a manganese-coated gold microwire electrode." Analytica Chimica Acta 710(0): 50-57.

Salaün, P., K. Gibbon-Walsh and C. M. G. Van Den Berg (2012). Speciation of inorganic arsenic in marine waters by stripping analysis at a gold microwire electrode.

Salaun, P., K. B. Gibbon-Walsh, G. M. S. Alves, H. M. V. M. Soares and C. M. G. van den Berg (2012). "Determination of arsenic and antimony in seawater by voltammetric and chronopotentiometric stripping using a vibrated gold microwire electrode." Analytica Chimica Acta 746: 53-62.