Rapid isotopic analysis of uranium particles by laser ablation MC-ICP-MS

Abstract

We present a methodology for characterizing the isotopic composition of uranium (U) in μm-scale particles by laser ablation multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Analyses were performed using two U particle materials, ²³⁵U-enriched Certified Reference Material (CRM) U200 and depleted uranium (DU) produced by Savannah River National Laboratory (SRNL). The laser was rastered over the sample surface and the signal derived from each individual particle was integrated separately and reduced using a bespoke data reduction package, including application of corrections for instrumental mass bias and ion counter gains. Accurate ²³⁴U/²³⁸U, ²³⁵U/²³⁸U and ²³⁶U/²³⁸U ratios were obtained with percent-level precision in samples with isotopic compositions spanning >2 orders of magnitude, including successfully resolving ²³⁴U and ²³⁶U abundances of <10 ppm and <80 ppm respectively in SRNL-DU. Comparable results obtained by laser ablation (LA) MC-ICP-MS and large geometry—secondary ionization mass spectrometry (LG-SIMS) indicate that laser ablation can provide valuable information when rapid U isotopic analysis of environmental samples is required.