Mass-spectrometric determination of iodine-129 using O-CO mixed-gas reaction in inductively coupled plasma tandem quadrupole mass spectrometry.

This paper presents a mass-spectrometric method for determining the radionuclide iodine-129 (I) from the significant amount of interference in inductively coupled plasma tandem quadrupole mass spectrometry (ICP-MS/MS) using a dynamic reaction cell passing a mixture gas of O and CO. Thus far, mass spectrometry analysis of trace amounts of I has been hampered by the presence of xenon-129 (Xe) and the formation of polyatomic ions from excess amounts of stable isotope I. In this study, flowing a mixture gas of O and CO into the dynamic reaction cell (Q2) successfully removed both Xe interference and polyatomic interference (IH) in the analysis of I in ICP-MS/MS. The resulting ratio of (background noise of m/z 129)/I was 4.6 × 10 ± 3.3 × 10, which enables the analysis of 10 mBq/L of I in the presence of 100 mg/L of stable I without chemical separation. The detection limit of this method was 0.73 mBq/L (= 0.11 ng/L) with an APEX-Q sample inlet desolvation device. For demonstration purposes, spike and recovery analysis of rainwater was performed, and good agreement between the spiked and recovered amounts was achieved.