Determination of mercury, arsenic and cadmium in fish by neutron activation

Determination of mercury, arsenic and cadmium in fish has been carried out by neutron activation followed by chemical separation to remove the interfering activities of copper, zinc etc. The standard and the samples were counted for 77 keV gamma-rays of 65 hr 197Hg, 336 keV gamma-rays of 115In from 53,5 hr 115Cd (after equilibrium) and 559 keV gamma-rays of 26.4 hr 76As on a NaI(Tl) crystal in conjunction with a 400-channel pulse-height analyser. The minimum detection limit was one nanogram pro mercury, 15 nanograms for cadmium and one nanogram for arsenic for the total sample volume. The counting errors at the detection limits were around 15%, 9% and 6%, respectively. Some of the common varieties of fish have been analysed and their results are presented. The mean concentrations of mercury, cadmium and arsenic in fish are 43.7 ng/g, 47.3 ng/g and 543.1 ng/g, respectively. Only the edible muscle tissue samples were used for analysis. (T.G.)