Determination of mercury by radiorelease of 109Cd from a diethyldithiocarbamate chelate and liquid scintillation counting

A radioanalytical procedure is described in which Hg2+, in an aqueous solution, is brought into contact with Cd-109-radiolabeled diethyldithiocarbamate (DDTC), in an organic phase. Because Hg2+ forms a much more stable chelate with DDTC than does Cd2+, it displaces (radioreleases) Cd-109 into the aqueous phase. This latter activity is linearly related to the concentration of Hg(II) in the sample solution, with excellent linearity down to similar to 5 ppb. Response factors are reported for a number of ions which may interfere with the determination. Major interferents include Cu2+, Ag+, and Pb2+.