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

Abstract

Wet digestion procedures using acid mixtures of HNO 3/H 2SO 4/HClO 4 and HNO 3/H 2SO 4 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 HNO 3/H 2SO 4 was also investigated for determination of Cr. All the acid mixtures tested were found to be satisfactory, but, for reasons of safety, HNO 3/H 2SO 4 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.