Direct Uranium Isotopic Analysis of Swipe Surfaces by Microextraction-ICP-MS

The ability to directly measure uranium isotope ratios on environmental swipes has been achieved through a solution-based microextraction process and represents a significant advancement toward the development of a rapid method to analyze international nuclear safeguard samples. Here, a microextraction probe is lowered and sealed onto the swipe surface, and analytes within the sampling site (similar to 8 mm(2)) are dissolved and extracted into a flowing solvent of 2% nitric acid (HNO3). The mobilized species are subsequently directed into an inductively coupled plasma-mass spectrometer (ICP-MS) for accurate and precise isotope ratio determination. This work highlights the novelty of the sampling mechanism, particularly with the direct coupling of the microextraction probe to the ICP-MS and measurement of uranium isotope ratios. The preliminary method detection limit for the micro-extraction-ICP-MS method, utilizing a quadrupole-based MS, was determined to be similar to 50 pg of U-238. Additionally, precise and accurate isotope ratio measurements were achieved on uranium reference materials for both the major ((UU)-U-233-U-/238) and minor(U-234/ U-238 and U-236/U-238), ratios. While the present work is focused on directly measuring uranium isotopic systems on swipe surfaces for nuclear safeguards and verification applications, the benefits would extend across many applications in which direct solid sampling is sought for elemental and isotopic analysis.

Automated summary

A novel solution-based microextraction process has been developed to directly measure uranium isotope ratios on environmental swipes, which represents a significant advancement towards analyzing international nuclear safeguard samples rapidly.