Determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in milk, cheese and chocolate

Combined analytical procedures consisting of wet digestion step followed by instrumental determination - differential pulse cathodic stripping voltamm etry (DPCSV) or electrothermal atomic absorption spectrometry (ETAAS) - as well as a direct analysis method - slurry sampling ETAAS - for the determin ation of Cd, Co, Cr, Cu, Fe, Ni and Pb in milk, cheese and chocolate are de scribed and compared. Wet digestion using a mixture of HNO3-HClO4-H2O2 is p roposed for complete matrix decomposition prior to trace analyte determinat ion by DPCSV or ETAAS. A mixture of HNO3-H2O2 is used for slurry preparatio n. Optimal instrumental parameters for trace analyte measurements are prese nted. The reliability of the procedures has been verified by analyzing standard r eference materials. Results obtained are in good agreement with the certifi ed values and the relative standard deviations (for these results) are in t he range 5-10 % for wet digestion DPCSV or ETAAS and 3-9 % for slurry sampl ing ETAAS in the range of 2 mu g.g(-1) (Cd) to 12 mu g.g(-1) (Fe).