Development of anion-exchange high-performance liquid chromatography-inductively coupled plasma mass spectrometry methods for the speciation analysis of inorganic selenium and iodine in groundwater

Abstract

This work presents the first report of a method for simultaneous speciation of inorganic selenium and iodine using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Baseline separation of selenite, selenate, iodide and iodate within a single chromatographic run of 10 min was achieved with the optimized mobile phase of 3 mM ammonium citrate, 25 mM ammonium perchlorate and 2% (v/v) methanol at pH 8.5. The mass spectrometric operating conditions were optimized to detect selenium and iodine simultaneously. Potential matrix effects were addressed and corrected using the standard addition method, and the recoveries (95.7–103%) were satisfactory. The repeatability and intermediate precision were satisfactory (the coefficients of variation were all less than 5% and 8%, respectively). The obtained detection limits were 22 ng L⁻¹ and 23 ng L⁻¹ for selenite and selenate, respectively, and 4.3 ng L⁻¹ and 5.4 ng L⁻¹ for iodide and iodate, respectively, which allows for the speciation of selenium and iodine in groundwater at the ultra-trace level. Groundwater samples collected from a candidate site for the Chinese high-level radioactive waste repository were analyzed. Within the three different groundwater samples, selenate was observed to be the dominant Se species; in addition, the iodide concentration increased and the iodate concentration decreased with increasing sampling depth. With its satisfactory sensitivity and accuracy, this method provides a promising tool for studying the environmental behaviors of selenium and iodine, thereby supporting safety assessments of high-level radioactive waste repositories.