Analytical Sciences

Determination of ¹²⁹I in Fukushima Soil Samples by ICP-MS with an Octopole Reaction System

Takeshi OHNO,* Yasuyuki MURAMATSU,* Chiaki TOYAMA,* Kazumi NAKANO,** Shinichiro KAKUTA,** and Hiroyuki MATSUZAKI***

*Department of Chemistry, Faculty of Science, Gakushuin University, Mejiro 1-5-1, Toshima, Tokyo 171-8588, Japan
**Agilent Technologies, Chemical Analysis, Japan Application Center, Takakura, Hachioji, Tokyo 192-8510, Japan
***Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan

A method was developed for the determination of ¹²⁹I in soil samples that uses an ICP-MS equipped with an octopole reaction system. Oxygen was used as the reaction gas for reducing the background intensity of m/z 129, principally by ¹²⁹Xe⁺. The contribution of polyatomic ions, such as ¹²⁷IH₂⁺, could be effectively corrected for by assuming a production ratio (¹²⁷IH₂⁺/¹²⁷I⁺ = 3 × 10⁻⁸). The measured ¹²⁹I/¹²⁷I ratios in a NIST standard solution and Fukushima soil samples are consistent with the expected value within the analytical error. This method provides a powerful tool for investigating radioiodine contamination in Fukushima and elsewhere.

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