The selection of chelators in the pre concentration system Flow Injection Knotted Reactor Flame Atomic Absorption Spectrometry(FI KR FAAS) and their corresponding experimental conditions were studied. Dithione was found to have advantages over the other two chelators with a higher concentration efficiency. Interferences from alkali and alkaline earth elements were overcome; mutual interferences between heavy metals were avoided. Concentration factors of 23 4-69 3 were obtained, with the detection limits of 1 61-2 56 μg/L. The method developed was used to determine certified biological reference materials of human hair, pig liver and sea prawn, and the results agreed well with the certified values, relative standard deviations of the determinations were in the range of 2 10%-3 02%.
