Copper catalyzes hydrocarbon oxidation
Ethanol is used increasingly in gasoline as a blending component. Contaminants can cause problems in the engine. For example, traces of copper catalyze the oxidation of hydrocarbons. As a consequence, polymer compounds can form that can lead to deposits and blockages in the fuel system. Specifications EN 15376 and ASTM D 4806 describe the minimum requirements for ethanol that is blended with gasoline and allow a copper content of 100 μg/kg. By contrast, standard ASTM D 5798 sets the copper content in ethanol-gasoline blends E75–E85 at 70 μg/L.
Using voltammetry, copper can be measured without any sample preparation in pure ethanol or ethanol-gasoline blends (E85, 85% ethanol and 15% gasoline) in the range between 2 and 500 μg/kg.