Determination of cadmium using radiochemical neutron activation analysis

A method has been developed for the determination of cadmium in samples of food and biological materials using neutron activation analysis with radiochemical separation. The irradiated sample is digested in presence of cadmium carrier, with a nitric-perchloric mixture, evaporated to dryness, dissolved in 6M HCl and placed onto an ion exchange column loaded with Dowex 1-X8 resin in chloride form and conditioned with HCl 6M. The cadmium is retained in the resin. After a washing procedure with several portions of HCl of decreasing concentration, the cadmium is eluted with an ammonia-ammonium chloride buffer. The activity of 115mIn which is in equilibrium with 115Cd, is measured using a NaI(Tl) well type detector. The method has been evaluated by analyzing certified reference materials with cadmium concentrations covering a range of 0.020 to 200 mg.kg-1. The agreement of the results with the certified values is within 95%, which gives an indication of the sensitivity and accuracy of the proposed method.