A preliminary study of rapid measurements of aqueous 210Po by accelerator mass spectrometry

Abstract

Polonium-210 (²¹⁰Po) is a toxic radioisotope naturally present in freshwater and groundwater that threatens the safety of drinking water supply. Designed for rapid analyses, a new procedure was tested for measuring aqueous ²¹⁰Po by accelerator mass spectrometry (AMS). Since the longer-lived polonium isotopes ²⁰⁸Po and ²⁰⁹Po suffer from atomic isobaric interferences, we normalized the ²¹⁰Po ion beam to a beam of ¹⁹⁷Au as the reference isotope. ²¹⁰Po and ¹⁹⁷Au solutions were co-precipitated with Ag⁺ and S²⁻ to form the stable compound Ag₂S. This method homogeneously precipitated these two isotopes of different elements and provided good electrical and thermal conductivity when the dried solid was pressed into a target for use in a Cs⁺ sputter ion source. Beams of atomic Po⁻ were charge changed, and the Po³⁺ ion was used for subsequent mass and energy analysis. Ion beams of ≥0.20 counts per second per femtogram of ²¹⁰Po in a target were produced. The measured and prepared ²¹⁰Po/¹⁹⁷Au ratios showed a good linear response when the quantity of ²¹⁰Po was prepared in a dilution series. With a counting time of less than 1.5 hours per target, the procedure indicated a ²¹⁰Po detection limit of 20 mBq (0.12 fg), supporting the next phase of development with environmental aqueous samples.