Mercury Detection in Seawater Using a Mercaptoacetic Acid Modified Gold Microwire Electrode

It is demonstrated here that it is possible to determine mercury in chloride containing media like seawater by anodic stripping voltammetry using a modified electrode. A gold microwire electrode is modified using mercaptoacetic acid (MAA) to eliminate the problem of calomel formation, allowing the mercury to become fully removed from the electrode surface after each scan. In a synthetic salt solution of KNO3 the sensitivity for mercury was found to be improved by the surface modification. In seawater the sensitivity was not significantly improved possibly because of complexation of the mercury by the abundant chloride; however, the MAA coating prevented the formation of calomel causing the background scan to be free of mercury. Measurements in seawater at various pH values demonstrated that mercury detection is possible at natural pH (around 8); however, best sensitivity was attained at pH 4.8 with a deposition time of 3 min. A peak for copper occurred at more negative potential but did not interfere at this pH. The calibration was linear between 0 and 37 nM mercury with a limit of detection of 1 nM mercury.

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