Determination of manganese and chromium in foods by atomic absorption spectrometry after wet digestion

Wet digestion procedures using acid mixtures of HNO3/H2SO4/HClO4 and HNO3/H2SO4 were investigated for their effectiveness for decomposition of food samples prior to determination of manganese (Mn) and chromium (Cr) by flame and Zeeman graphite furnace atomic absorption spectrophotometry. The addition of hydrofluoric acid (HF) to the mixture of HNO3/H2SO4 was also investigated for determination of Cr. All the acid mixtures tested were found to be satisfactory, but, for reasons of safety, HNO3/H2SO4 was the method of choice. No apparent matrix interferences or losses of analytes were encountered with the method used. Analysis of selected food samples found relatively high levels of Mn and Cr in most cereal products. Meats, dairy products (except for Cr in cheese), vegetables and fruits contained relatively low levels of both elements.