Novel approach for the determination of 238Pu by thermal ionization mass spectrometry (TIMS) using interfering element correction methodology

A novel approach using interfering element correction (IEC) methodology is presented for the determination of Pu-238 in Pu by thermal ionization mass spectrometry (TIMS). The IEC methodology is based on the use of U-235 as a monitor isotope to correct for the ubiquitous isobaric interference of U-238 at Pu-238. The procedure involves the addition of enriched U-235 (>90 atom%) externally to the Pu sample. The U-238/U-235 atom ratio in the sample is determined experimentally by monitoring the intensities of ions with m/z 254 and 251, corresponding to (UO+)-U-231 and (UO+)-U-235, respectively. Subsequently, Pu-238/Pu-239 atom ratio is determined by using Pu+ ion at different heating temperatures of vaporization and ionization filaments. The methodology is evaluated using NIST-SRM 947 isotopic reference material with Pu-238 abundance close to 0.25 atom% and a synthetically prepared sample containing about 2 atom% of Pu-238. The approach is simple and holds promise for the characterization of new reference materials of Pu-238 using TIMS. (C) 2004 Published by Elsevier B.V.