Determination of99Tc in rain and dry fallout by ICP-MS

Due to the difficulty of⁹⁹Tc analysis, data are insufficient for discussing its behavior in the environment. In this study, we focused on the determination of⁹⁹Tc in rain and dry fallout samples. The samples were collected monthly at Nakaminato, Japan, from June 1993. They were concentrated by heating on a hot plate without any loss of Tc. The solution was filtrated and then a liquid-liquid extraction (LLX) with trioctylamine (TOA), which works as a liquid anion exchanger, was carried out. Technetium was extracted from 5% HNO₃ solution into the organic phase with a high extractability. After being back-extracted from TOA/xylene into 1M K₂CO₃, LLX with cyclohexanone was used to remove ruthenium, which has a stable isotope of mass 99. Technetium was back-extracted into deionized water, and the solution was measured by inductively coupled plasma mass spectrometry (ICP-MS). The average recovery under the experimental conditions was 67% and the instrumental detection limit was 0.04 ppt (0.03 mBq/mL).