Equipment pre-treatment

The voltammetric cell should be soaked in 2 mol/L acid prior to first use. During regular use it is sufficient to rinse the cell with pure water, unless the cell has become contaminated with very high metal levels when an acid rinse is recommended. Adsorption takes place which can cause the peak heights to decrease during measurements in freshly cleaned cells (Cuculic and Branica, 1996). All cell materials and components adsorb but the least problems are observed with quartz. It is therefore not advisable to rinse the cell with acid between measurements to allow the cell and electrode walls to become conditioned with seawater and the metal levels being determined. 

The reference electrode normally has a slow leak into the solution at a rate of a few microlitre per hour. It is therefore advisable to ensure the filling solution (normally 3 mol/L KCl) is clean, either by using a high grade salt for its preparation, or by piuification. Double-junction reference electrodes exist and these are useful for instance if silver or sulphide are to be determined due to the presence of ionic silver in the silver reference electrode cartridge. 

The counter electrode consists normally of a platinum wire or a glassy carbon electrode. Either of these electrodes is suitable for trace analysis and requires no pre-treatment, unless platinum is being determined in seawater in which case a glassy carbon counter electrode should be used. 

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