Determination of copper in clarified apple juices

Inorganic copper compounds are not considered as synthetic fertilizers for apple trees as they are traditional fertilizers. Thus, they are used in organic farming for soil or foliar applications. The European Union is for health reasons interested in reducing copper in apple orchards. Because the fertilizer application rate affects the nutrition of apples, the applied copper might also be reflected In the copper concentration of apple juices. Thus, the determination of copper Is of concern for investigating the application of copper-containing fertilizers. Samples of clarified apple juice commercially available in the European market were analyzed for their copper content. Prior to quantification by inductively coupled plasma-optical emission spectrometry, the juices were processed by a microwave-assisted digestion system using HNO₃. All samples were also measured directly after dilution with HNO₃. The copper concentrations measured using both methods were all below the limit of detection (17 μg/L).