STRIPPING VOLTAMMETRIC DETERMINATION OF HEAVY METALS IN VEGETABLE OILS

Abstract

The possibility of stripping-voltammetric determination of Zn, Cd, Pb, Cu, Hg trace amounts in vegetable oils without the use of mineralization procedure has been demonstrated. It has been established that high sensitivity of the method (<0.001 mg/dm>3) can be achieved for Zn, Cd, Pb, Cu by cathodic accumulation on the surface of the amalgamated silver indicator electrode, and by the accumulation of mercury on the electrode containing 58 % Au, 34 % Cu, 8% Ag. The amount of the deposited metal has been determined by the magnitude of the anodic current in an aqueous-acetone electrolyte containing formic (Zn, Cd, Pb, Cu) or sulfuric (Hg) acid additives. Analysis of twelve refined and unrefined vegetable oil samples (sunflower, olive, linseed, rapeseed, and corn) showed the presence of trace impurities of zinc (0.6–9.6 mg/dm3), lead (0.02–0.09 mg/dm3), and copper (0.02–0.17 mg/dm3). Additional traces of mercury (0.002–0.009 mg/dm3) were detected in eight oil samples and cadmium traces (0.02–0.05 mg/dm3) in nine samples. In general, the content of toxic metals in the samples does not exceed the permissible levels governed by technical regulations.