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Electrochemical determination of organic surface active substances in model and natural sea water with Au(111) monocrystal electrode

The applicability of Au(111) monocrystal electrode for the determination of the amount of surface active organic substances was investigated using cyclic voltammetry, CV, and phase selective alternating current voltammetry, PSACV. The behaviour of the electrode was tested in a simple sea water model solution (0.55 M NaCl or 0.55 M NaCl plus 9.6 x 10-4 M KBr), as well as in the natural sea water samples from northern Adriatic. Surface active organic molecules used for model adsorption investigations were Triton X-100, T-X-100, and humic acid, HA. Their behaviour in NaCl medium is discussed and typical CV and PSACV curves are compared for Cl- and Br- media. The characteristic of Au(111) surface reconstruction to be lifted by the adsorption of anions such as Cl- or Br- was used for analytical purposes, since competition in adsorption between inorganic anions and organic molecules changes strongly the reconstruction behaviour of Au(111). Calibration curves for T-X-100 and HA in model sea water were constructed and were used for the determination of the relative concentrations of surface active molecules in natural sea water samples. PSACV method was chosen as more reproducible and practical since no deaeration of the solution was necessary.

Au(111) Surface active substances; Electrochemical determination; Sea water; Gold(111) electrode; Triton-X-100; Humic acid

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