VOLTAMMETRIC DETERMINATION OF TRACE AMOUNTS OF MERCURY WITH A CARBON PASTE ELECTRODE MODIFIED WITH AN ANION-EXCHANGER

A carbon paste electrode modified with a liquid anion exchanger (Amberlite LA2) was used for the voltammetric determination of mercury(II). Mercury is pre-concentrated, as tetrachloromercurate(II), onto the surface of the modified electrode only by the ion-exchange effect of the modifier without application of potential. After exchange of the medium the accumulated amount of mercury(II) is determined by differential pulse anodic stripping voltammetry in a blank electrolyte solution. The response depends on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 1 mug Hg(II)/l when a suitable time for preconcentration was chosen. Preconcentration for 5 min yields a linear calibration graph for concentrations up to 1000 mug Hg(II)/l. The effect of other ions on the determination of mercury and the applicability of the method to the analysis of phenylmercury compounds in pharmaceutical preparations were investigated.