Improved approach for routine monitoring of I activity and I/I atom ratio in environmental samples using TMAH extraction and ICP-MS/MS.

To reconstruct I deposition and identify the source of radioiodine due to the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, I activity and I/I atom ratio should be obtained by preparing and analyzing large numbers of samples economically. In this study, great efforts were made to realize mild TMAH (tetramethyl ammonium hydroxide) extraction of environmental samples at 90 °C to obtain solutions suitable for the following triple-quadrupole inductively coupled plasma-mass spectrometry (ICP-QQQ) MS/MS mode analysis. After releasing iodine from organic matter in the TMAH extraction solution via KSO oxidation, organic matter was removed effectively by solvent extraction and back-extraction to avoid a serious matrix effect during ICP-QQQ analysis. At the same time, interfering elements, especially, Mo, Cd, and In were also removed effectively, to avoid their undesirable interferences during mass spectrometric analysis. In addition, 0.01% (NH)SO was selected to introduce I into ICP-QQQ to ensure there was no memory effect and a stable signal was gotten. Subsequently, ICP-QQQ MS/MS mode was applied to further eliminate polyatomic interferences (I(H and D), MoO, InO, and CdO) and isobaric interference from Xe. Finally, the developed method was successfully applied to measure I/I atom ratios ((2.61-27.0) × 10) and I activities (3.51-11.4 mBq kg) in soil samples. The developed method allows a greater number of ordinary laboratories to participate in the field of radioiodine analysis.