Rapid and simple determination of heavy metals in foods [cadmium, lead and copper in brown rice and other foods]: Application of wet digestion and iodide-MIBK [methyl iso-butyl ketone] extraction

Wet digestion was done in a Soxhlet flask equipped with a digestion cap. Sulfuric acid 1ml, 60% perchloric acid 3ml and nitric acid were added and the mixture was heated. After the digestion, water was added to 25ml. Sulfuric acid 2ml and 50w/v% potassium iodide were then added and cadmium, lead and copper were extracted with MIBK 5ml (potassium iodide-MIBK extraction). When fish oil and brown rice were digested by this method, the time required for digestion was only a quarter to half that of the usual method, and the contamination from reagents and glassware was reduced. Analytical accuracy and precision for cadmium and copper in brown rice were good. The results of potassium iodide-MIBK extraction and DDTC-MIBK extraction of cadmium in brown rice showed a good correlation. This method is rapid and simple, and should be suitable for routine analysis of cadmium in brown rice and of other metals in foods.