Second interlaboratory comparison study for the analysis of Pu-239 in synthetic urine at the mu Bq (similar to 100 aCi) level by mass spectrometry

As a follow up to the initial 1998 intercomparison study, a second study was initiated in 2001 as part of the ongoing evaluation of the capabilities of various ultra-sensitive methods to analyze Pu-239 in urine samples. The initial study(1) was sponsored by the Department of Energy, Office of International Health Programs to evaluate and validate new technologies that may supersede the existing fission tract analysis (FTA) method for the analysis of Pu-239 in urine at the muBq/l level. The ultra-sensitive techniques evaluated in the second study included accelerator mass spectrometry (AMS) by LLNL, thermal ionization mass spectrometry (TIMS) by LANL and FTA by the University of Utah. Only the results for the mass spectrometric methods will be presented. For the second study, the testing levels were approximately 4, 9, 29 and 56 muBq of Pu-239 per liter of synthetic urine. Each test sample also contained Pu-240 at a Pu-240/Pu-239 atom ratio of similar to0.15 and natural uranium at a concentration of 50 muBq/ml. From the results of the two studies, it can be inferred that the best performance at the muBq level is more laboratory specific than method specific. The second study demonstrated that LANL-TIMS and LLNL-AMS had essentially the same quantification level for both isotopes. Study results for bias and precision and acceptable performance compared to ANSI N13.30 and ANSI N42.22 have been compiled.