Iodine oxidation-driven enhancement in preconcentration and ICP-MS/MS detection of 129I in environmental water

Abstract

¹²⁹ I is a key isotope for assessing environmental safety at nuclear contaminated sites. The routine monitoring of ¹²⁹I in contaminated water demands a more sensitive and efficient method. In this study, a modified chemical vapor generation (CVG) method was developed for the determination of ultra-trace ¹²⁹I in water samples by ICP-MS/MS. Residual I⁻ on the spray chamber wall is oxidized to I₂ vapor by NaNO₂, synchronously enhancing both ¹²⁹I and ¹²⁷I signals by approximately 10 to 30 times. Notably, the method required only 0.2 mL of sample and exhibits reduced carryover effects compared with conventional CVG and PCVG. The limit of detection (LOD) of the developed method for ¹²⁹I was 0.146 pg mL⁻¹, which is approximately one order of magnitude lower than that of previous methods. In addition, a concise iodine preconcentration method was also developed for water samples. Iodide (I⁻) was oxidized to volatile I₂, which was trapped in a small volume of 0.005% NaHSO₃ solution for direct measurement, avoiding the conventional addition of an ¹²⁷I carrier. The current method yielded ¹²⁹I results for contaminated groundwater samples that were consistent with the traditional approach. Overall, the developed method is accurate, robust, and convenient for the determination of ultra-trace ¹²⁹I in environmental water, making it well-suited for routine monitoring applications.