Determination of mercury in process and lagoon waters by inductively coupled plasma-mass spectrometric analysis after electrochemical preconcentration: comparison with anodic stripping at gold and polymer coated electrodes

A combined electrochemical-inductively coupled plasma-mass spectrometry (EC-ICP-MS) method for the determination of trace mercury in water samples is presented. It takes advantage of the electrochemical preconcentration of mercury onto a gold spiral electrode followed by ICP-MS analysis after the electrochemical reoxidation of deposited mercury in pure supporting electrolyte. The advantages of the EC-ICP-MS approach with respect to conventional ICP-MS, are the increased sensitivity and the elimination of the effect of interfering substances eventually present in the sample. EC-ICP-MS is applied to the determination of nanomolar and subnanomolar concentrations of mercury(II) ions in real samples such as process waters (from a chlor-alkali plant) and lagoon waters (from Venice channels). Analytical performances obtained by EC-ICP-MS are discussed and compared with those obtained by anodic stripping voltammetry at gold and at Tosflex-coated glassy carbon electrodes.