Determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in Milk, Cheese and Chocolate

Abstract.

 Combined analytical procedures consisting of wet digestion step followed by instrumental determination – differential pulse cathodic stripping voltammetry (DPCSV) or electrothermal atomic absorption spectrometry (ETAAS) – as well as a direct analysis method – slurry sampling ETAAS – for the determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in milk, cheese and chocolate are described and compared. Wet digestion using a mixture of HNO₃-HClO₄-H₂O₂ is proposed for complete matrix decomposition prior to trace analyte determinati on by DPCSV or ETAAS. A mixture of HNO₃-H₂O₂ is used for slurry preparation. Optimal instrumental parameters for trace analyte measurements are presented.

The reliability of the procedures has been verified by analyzing standard reference materials. Results obtained are in good agreement with the certified values and the relative standard deviations (for these results) are in the range 5–10% for wet digestion DPCSV or ETAAS and 3–9% for slurry sampling ETAAS in the range of 2 μgċg⁻¹ (Cd) to 12 μgċg⁻¹ (Fe).