Measurement of trace 129I in natural water with ozone reaction for effective separation of spectral interferences

Tandem quadrupole inductively coupled plasma mass spectrometry has the potential capability to measure ¹²⁹I at extremely low concentration if spectral interferences from ¹²⁹Xe and ¹²⁷I¹H₂ can be eliminated effectively. Ozone was introduced as the reaction gas, resulting significantly improved reactions of (¹²⁹I⁺→¹²⁹I¹⁶O⁺) and (¹²⁹I⁺→¹²⁹I¹⁶O₂⁺), and permitted the highly sensitive measurement of ¹²⁹I⁺ as ¹²⁹I¹⁶O⁺ and ¹²⁹I¹⁶O₂⁺, helping eliminate spectral interferences related to ¹²⁹Xe⁺ and ¹²⁷I¹H₂⁺. In isotopic ratio (¹²⁹I/¹²⁷I) analysis by measuring (¹²⁹I⁺→¹²⁹I¹⁶O₂⁺)/(¹²⁷I⁺→¹²⁷I¹⁶O₂⁺), a blank ratio of 6.7 × 10⁻¹⁰ can be realized for a solution of 500 μg/mL natural iodine, improved by one order of magnitude than the best performance previous reported. This technique contributes to the measurement of trace level ¹²⁹I, a radionuclide of iodine attracting attentions as a geochemical tracer related to the development and civilian use of nuclear energy as well as a regulated radionuclide with guidance levels in drinking water established by the World Health Organization.