Bioavailability of cadmium and lead in cocoa: comparison of extraction procedures prior to size-exclusion fast-flow liquid chromatography with inductively coupled plasma mass spectrometric detection (SEC-ICP-MS)

Abstract

Fifteen extraction methods were investigated for the recovery of different classes of Cd and Pb species in 8 different cocoa powder samples. The procedures targeted water-soluble compounds, polypeptide and polysaccharide complexes and compounds soluble in simulated gastrointestinal conditions. The extracts were analysed by size-exclusion fast-flow liquid chromatography with ICP-MS detection. The detection limit was 0.5 µg l⁻¹ and the RSD was less than 7.5%. Cd and Pb were very firmly bound to the insoluble matrix components, of which the binding capacity exceeded about 1000 times the naturally present metal levels. Cocoa powder may show possible detoxifying properties for Pb and Cd by binding them into stable complexes, which are resistant in gastrointestinal conditions. The maximum average recovery for Cd and Pb was, respectively, 15% and 5% of the total metal present.