The use of polarographic methods for the evaluation of the stability of element species in food extracts

Summary A new approach to the evaluation of binding stabilities and capacities of metals in their intrinsic matrices is presented. The applicability of polarography without previous matrix separation is demonstrated by the example of copper and nickel in food extracts. In such native solutions the interdependence of the metals and their potential binding partners is examined. The results show that copper is very specifically bound to sulfhydryl groups, whereas nickel is bound more or less unspecifically. Distribution patterns for binding stabilities and capacities are given for soybean flour and mate tea extract. Generally, copper has higher stabilities and capacities than nickel. As a special feature the displacement of nickel by copper is demonstrated.