DETERMINATION OF HEAVY-METALS IN CONCENTRATED REFINED SUGAR AND RAW SYRUPS WITH DIFFERENTIAL-PULSE POLAROGRAPHY AND ANODIC-STRIPPING VOLTAMMETRY

The behavior of copper, lead, cadmium, and zinc is investigated in concentrated solutions of refined beetroots sugar. The diffusion coefficients are found to decrease less than predicted by the Walden's rule, so trace determinations down to 10(-7) M were measured by differential pulse polarography (DPP). Using anodic stripping voltammetry at a mercury film electrode, it was found that the refined sugar of alimentary grade contained: 57 (Cu), 34 (Zn), 1 (Cd), and 6 (Pb) mug/kg of dry sugar. For industrial syrups, resulting from a treatment by lime and water vapor of the raw material, some problems were encountered. Determination of copper and zinc was impossible, while that of lead and cadmium was possible after one liter of diluted syrup, at about 250 g l(-1), had been treated with 20 g of activated carbon to absorb the major part of organic impurities. The lead and cadmium contents were found to be 20 (Pb) and 3.5 (Cd) mug kg-1.