STRIPPING VOLTAMMETRIC DETERMINATION OF MERCURY AT MODIFIED SOLID ELECTRODES I - DEVELOPMENT OF THE MODIFIED ELECTRODES

The paper describes the development of modified thick film graphite el ectrodes (TFGEs) for the stripping voltammetric determination of mercu ry. It is well known that mercury is determined best using gold electr odes. Therefore we have decided to modify the surface of a solid graph ite containing electrode so that after the preliminary chemical or ele ctrochemical reduction metallic gold appears in the modified layer on the electrode. Then mercury is deposited electrochemically from the sa mple solution on the metallic gold and is determined by anodic strippi ng voltammetry. To this end three different methods for the electrode modification have been chosen: One modified with a gold(III) solution from which gold was reduced chemically using various agents, one modif ied with a mixture of a gold(III) salt and Nafion and one modified wit h different insoluble gold(III) complexes. In method 2 as well as in m ethod 3 the gold(III) was reduced cathodically By virtue of their life time, their reproducibility and their sensitivity we preferred the ele ctrodes modified by method 3 using a gold(III)-pyrrolindinedithiocarba mate (PDC) complex. Analytical applications for the mercury determinat ion using this modified electrodes and the efficiency of this procedur e will be published in a following paper. (C) 1998 Elsevier Science B. V. All rights reserved.