Stripping analyses of mercury using gold electrodes: Irreversible adsorption of mercury

The electrochemical deposition and stripping of mercury on gold surfaces wa s investigated to assess whether gold electrodes would return to mercury-fr ee states after stripping analyses. X-ray photoelectron spectroscopy studie s demonstrate the presence of mercury on gold foil electrodes that have und ergone controlled-potential deposition procedures in Hg2+ solutions (10 nM- 0.1 mM) followed by stripping and cleaning in mercury-free electrolyte. Res ults show that mercury is not completely removed electrochemically from the gold electrodes, even when the oxidizing potential is +2.5 V vs Ag/AgCl. B ulk electrolyses deposition and stripping procedures coupled with cold vapo r atomic absorption spectroscopic analyses of solutions after deposition an d stripping are also reported. Results suggest that the nature of the gold electrode is fundamentally altered by irreversible adsorption of mercury; t hat is, mercury is adsorbed during deposition and some of the mercury is re tained even after stripping and cleaning. The implications and strategies f or using stripping analysis and gold electrodes for the measurement of merc ury under the experimental conditions employed in this study are discussed.