Analytical Procedure for Technetium-99 in Seawater by ICP-MS

Abstract

An analytical procedure using inductively coupled plasma mass spectrometry (ICP-MS) was developed for determination of very low-level in seawater. Technetium in seawater was reduced and coprecipitated with 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 reagents. The procedure developed showed good recovery for '^Tc 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 concentration in coastal seawater.

Determination of technetium-99 in environmental samples: A review

“…A concentration of 0.01-0.3 mBq L -1 of 99 Tc in seawater from the Greenland Sea was detected in our laboratory during the years 2000-2008 (unpublished data), and 0.07 mBq L -1 in the Arctic seawater [47]. This is about one order of magnitude higher than that in the background area [37][38][39].…”

“…The accumulated deposition from weapons fallout is in the order of 500 mBq m -2 [35] and a 99 Tc concentration of 4-88 mBq kg -1 was reported in Japanese soils in 2002 [36]. In precipitation, the concentration of 99 Tc ranges from 20 to 60 µBq L -1 , while in seawater it is only some few µBq L -1 [37][38][39]. However, 99 Tc concentrations of 0.4 Bq kg -1 (dry mass) in Fucus vesiculosus from northwestern Spain [40], and of 0.1 Bq kg -1 (dry mass) from southern Spain have been observed, in areas where no direct 99 Tc contamination was reported [41].…”

“…Because of the week sorption of TcO 4 -in various environmental media, Tc is considered to be one of the most mobile radionuclides in the environment. Strong reductive reagents such as sulphite, meta-bisulphite, hydrazine or ascorbic acid are often applied to reduce TcO 4 -to lower oxidation states such as Tc(IV) [5,6,38,59]. Conversely, strong oxidants like bromine water, hydrogen peroxide, alkaline peroxide, hypochlorite, or persulphate, are employed to rapidly oxidize the lower oxidation state of Tc to TcO 4 - [60][61][62][63].…”

“…Since the concentration of 99 Tc in environmental water samples is normally very low, it requires sample pre-treatment to pre-concentrate 99 Tc. The enrichment of 99 Tc can be achieved by a few approaches, including evaporation [76], activated carbon adsorption [77], co-19 precipitation [21,38,40,59,75], and anion exchange chromatography [2,6] according to the volume and the salt content of the sample.…”

“…A hydroxide precipitation step is then added to remove transition metals and actinides, which easily form precipitate in alkali medium. The supernatant is neutralized and loaded to 38 an anion exchange column (AG1-×4). Most of the cations are removed to the effluent, after washing the column with water and diluted HNO 3 , and 99 Tc is then eluted with 10 mol L -1 HNO 3 in a small volume.…”