The reliable determination of mercury traces in sea water by subtractive differential pulse voltammetry at the twin gold electrode
Institute of Chemistry, Institute 4 Applied Physical Chemistry, Nuclear Research Centre (KFA), JuelichFederal Republic of Germany
Center for Marine Research, Institute “Rudjer Bošković”, Zagreb, CroatiaYugoslavia
In the marine environment, mercury has the greatest toxicological significance among the common metals. By combining several basic principles of advanced voltammetry, a reliable and accurate procedure with a determination limit of 1 ng l-1 has been developed. The complete method, which is necessary for application to sea water, consists of cathodic deposition under programmed polarization with intermittent short anodic pulses to strip the co-deposited copper usually present in sea water in substantially larger amounts than mercury, subsequent medium exchange to 0.1 M HClO4–2.5 × 10-3 M HCl, and differential pulse anodic stripping in the subtractive mode at a twin gold disc electrode system. Construction of the twin electrode (which has its two halves insulated from each other), characteristics of the stages of the voltammetric procedure and its performance are presented. The method is very flexible and can be adapted and simplified for application to other aqueous matrices and natural waters with mercury levels above 100 ng l-1. The data from a case study yielding a survey of the mercury content in the German North Sea coastal waters demonstrate the significance of this new analytical procedure for research and monitoring tasks in marine trace chemistry.