Voltammetric methods to quantify hazardous elements (Ni, Pb and Cd) in chocolate and cacao products

This study focuses on optimizing voltammetric methods to quantify three elements of toxicological interest (lead, cadmium and nickel) in 52 chocolate and cocoa-based products. Using microwave-assisted mineralization followed by anodic re-dissolution and differential pulse voltammetry, the methods demonstrated high sensitivity, precision, and low cost-efficiency for detecting trace metals in complex food matrices. Ni was the most abundant element followed by Pb and Cd. Results revealed Ni exceeds legal limits in over 50 % of samples. While concentrations of Cd were generally compliant with regulations, Pb levels surpassed legal limits in certain dark chocolate samples. The Ni concentration varies between the limit of quantification (23 μg kg⁻¹) and 12100 μg kg⁻¹ with an average of 2064 μg kg⁻¹. It is present in higher concentrations (8500–12100 μg kg⁻¹) in three samples of white chocolate. A dark chocolate cream produced by a famous industry, shows the highest concentration. Cadmium in the analysed samples is the element having the lowest concentrations. It is present in the range between the limit of quantification (37 μg kg⁻¹) and 610 μg kg⁻¹ with an average of 63 μg kg⁻¹. The highest concentration was quantified in a gianduia chocolate.