Determination of ultratrace amounts of plutonium in high saline groundwater by inductively coupled plasma mass spectrometry

Abstract

For determination of ultratrace amounts of plutonium in high saline groundwater, large-volume sampling and preconcentration are necessary. However, traditional co-precipitation methods, such as Fe(OH)3, Ca(OH)2–Mg(OH)2 and hydroxide-carbonate co-precipitation, are unable to meet the requirements of preconcentration of the ultratrace plutonium in high saline groundwater. In this paper, the ultratrace plutonium in high saline groundwater was concentrated by sequential co-precipitation with MnO2 and Fe(OH)3, and purified by two-stage anion-exchange separation on Dowex1 × 4 resin column. Quadrupole ICP-MS was employed for the determination of 239Pu with 242Pu spiked. After co-precipitation and purification, the major matrix elements were significantly decreased to μg mL−1 level and decontamination factor of uranium is better than 106. The detection limit for 239Pu in 50 L high saline water is 2.1 × 10−16 g L−1. Three high saline fountain samples (total dissolved solids more than 20 g L−1) from Dunhuang region of China were analyzed using this method. The concentrations of 239Pu in these samples were 0.48 ± 0.2 × 10−15, 1.40 ± 0.10 × 10−15 and 2.13 ± 0.21 × 10−15 g L−1 respectively. The recovery obtained for 7 pg of 242Pu spiked into real high saline-water samples was all above 70 %.