ANALYTICAL PROCEDURE FOR TC-99 IN SEAWATER BY ICP-MS

An analytical procedure using inductively coupled plasma mass spectrom etry (ICP-MS) was developed for determination of very low-level Tc-99 in seawater. Technetium in seawater was reduced and coprecipitated wit h iron hydroxide. The reduction of Tc by K2S2O5 at PH 4 was rapid and quantitative, and its coprecipitation with iron hydroxide at pH 9 was quantitative. A repetitive coprecipitation method using the same iron as coprecipitater showed no decrease of Tc recovery. Recovery of Tc in various steps of the procedure was examined, i.e., solvent extraction , anion and cation exchange. Background counting rate, with reference to ICP-MS, was extensively examined for Various kinds of acids and rea gents. The procedure developed showed good recovery for Tc-99 and low background counting rate at m/z 99 by ICP-MS. The detection limit was about 40 times lower than the conventional radioanalytical method. The present procedure was applied to determination of Tc-99 concentration in coastal seawater.