Determination of picogram amounts of uranium in micrometre-sized particles by isotope dilution mass spectrometry

In order to improve the analytical methods used in the field of particle analysis in nuclear safeguards, monodispersed micrometre-sized particles with certified uranium isotopic composition and uranium amount per particle are highly useful. In this study, picogram amounts of uranium in particle form were quantified in a candidate particle reference material for certification. The uranium amount per particle was determined using optical microscopy combined with Isotope Dilution Thermal Ionisation Mass Spectrometry (ID-TIMS). The uranium amount was verified using Isotope Dilution Multi Collection-Inductively Coupled Plasma Mass Spectrometry (ID-MC-ICPMS). The uranium amount per particle agreed well between the two techniques within the associated uncertainties. Both techniques are suitable for quantification of picogram amounts of uranium in particulate reference materials. The uranium particle material in this study was later used in a proficiency test (NUSIMEP-9) and eventually certified for the uranium isotopic composition of particles and the uranium amount per particle. Micro-manipulated uranium micrometer-sized particles under optical microscope, measured at picogram level by two mass spectrometric techniques.