Determination of cadmium in rice by microwave digestion and graphite furnace atomic absorption spectrometry

An analytical method for cadmium (Cd) in rice by microwave digestion and gr aphite furnace atomic absorption spectrometry (AAS) was developed. A sample of 0.50 g was predigested overnight in 7 mL of nitric acid. The mixture wa s treated with 2 mL of hydrogen peroxide solution and immediately exposed t o microwave irradiation. The digested solution was evaporated to just befor e dryness on a hotplate and then made up to 10 mL with 0.20m nitric acid. C d in the sample solution was determined by graphite furnace AAS using a cal ibration method. 0.5% ammonium dihydrogen phosphate/0.2% nitric acid and 2% ascorbic acid were used as matrix modifiers. Recoveries of Cd added to ric e were 97 similar to 108%, the CV was 1.6 similar to 63% and the detection limit was 5 ng/g. Cd was detected at 28 similar to 96 ng/g in polished rice , 18 similar to 226 ng/g in brown rice and 7 similar to 49 ng/g in cooked r ices.