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 wa s preconcentrated onto the surface of the modified electrode only by t he complexing effect of the modifier without application of potential (i.e. in open-circuit conditions). After exchange of the medium, the a ccumulated amount of mercury(II) was determined by differential pulse anodic stripping voltammetry. The response depended on the concentrati on of mercury in the bulk solution, preconcentration time, and other p arameters. The detection limit was 0.1 mug l-1 Hg(II) for a preconcent ration time of 15 min. Preconcentration for suitable times yielded a l inear 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 t o determine trace mercury in plant and sewage sludge samples with good results.