Determination of radiocobalt in seawater by successive extractions with the reagents of tris/pyrrolidine dithiocarbamato/bismuth(III) and ammonium pyrrolidindithiocarbamate and back-extraction with bismuth(III)

Method for the isolation of radioactive cobalt (including sup(58)Co and sup(60)Co) from a large volume of seawater and concentration in a small volume of chloroform as tris/pyrrolidine dithiocarbamato/cobalt(III), Co(PDC)sub(3), is described. The seawater was extracted first with Bi(PDC)sub(3) in chloroform for removing parts of foreign metals such as Hg, Ag, etc., and then added with ammonium pyrrolidindithiocarbamate, APDC, to complex with Co and possibly other ions and extracted into the organic phase. The final separation of Co from foreign ions in the organic phase was achieved by stripping with a Bi(III) solution. The overall recovery of radiocobalt activity was found to be about 96%. The established method can be applied for rapid and reliable determination of radiocobalt in seawater and other aqueous systems for environmental contamination. (author)