Preconcentration by Surface Complexation

Hydrophobic organic ligands added to a carbon-paste electrode, or immobilized on a chemically modified electrode, can be used for the accumulation of metal ions by the surface-complexation mechanism [89-91]. The same goal can be achieved by immobilized ion-exchangers such as natural or synthetic zeolites [89], clay minerals [92], silica [93] and ion exchange resins [94]  

28) HY is a protonated ligand, or a structural unit of the ion-exchanger. If less than 10 % of the recipient capacity is consumed, the surface concentration of the bound metal is linearly proportional to the concentration of metal ions at the electrode surface [95]  

The main advantage of this procedure is that neither a complexing agent nor an electrolyte is added to the sample solution. The metal ions are chemically collected and then transferred into an electrolytic solution for the voltammetric measurements [91]. 

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