STRIPPING VOLTAMMETRIC DETERMINATION OF TRACE AMOUNTS OF MERCURY USING A CARBON-PASTE ELECTRODE MODIFIED WITH 2-MERCAPTO-4(3H)-QUINAZOLINONE

A carbon paste electrode modified with 2-mercapto-4(3H)-quinazolinone was used for the voltammetric determination of mercury(II). Mercury was preconcentrated onto the surface of the modified electrode only by the complexing effect of the modifier without application of potential (i.e. in open-circuit conditions). After exchange of the medium, the accumulated amount of mercury(II) was determined by differential pulse anodic stripping voltammetry. The response depended on the concentration of mercury in the bulk solution, preconcentration time, and other parameters. The detection limit was 0.1 mug l-1 Hg(II) for a preconcentration time of 15 min. Preconcentration for suitable times yielded a linear calibration graph from 0.5 to 6000 mug l-1 Hg(II). For multiple determinations (5 runs), the relative standard deviation was 5% for a concentration of 100 mug l-1 Hg(II). The proposed procedure was used to determine trace mercury in plant and sewage sludge samples with good results.