THE EFFECT OF COMPLEXATION EQUILIBRIA ON THE RESPONSE OF CHEMICALLY MODIFIED ELECTRODES FOR THE DETERMINATION OF SILVER

The determination of silver using anodic stripping voltammetry at graphite electrodes modified with various macrocyclic thia ligands and a Nafion film was examined in different media. The electrode response is proportional to the stability constant of the silver complex with the immobilized thia ligand. In the presence of cyanide or thiosulfate ions in the silver solution, the signal is diminished according to the concentration of the foreign ligand and the value of the corresponding conditional stability constant. The effect of the accumulation time on the detected fraction of silver is reported, and the consequences for speciation studies are indicated.