TECHNICAL EQUIVALENCE BETWEEN PERKIN-ELMER DRCe AND ELAN 6000 FOR THE ANALYSIS OF 238U IN URINE BIOASSAY SAMPLES

The LLNL Bioassay Laboratory recently purchased a Perkin-Elmer DRCe ICP-MS (DRCe) to replace the existing Perkin-Elmer Elan 6000 ICP-MS (Elan 6000) used for the analysis of 238U in urine bioassay samples. In accordance with section 5.7.2 of DOE-STD-1112-98, 'The Department of Energy Laboratory Accreditation Program for Radiobioassay', this document demonstrates that the DRCe is technically equivalent to the Elan 6000. This paper documents: (1) Minor changes made in the procedure to improve the sensitivity; (2) Detection limits for the Elan 6000 and the DRCe; (3) Determination of the measurement uncertainty for the DRCe; and (4) Comparison of results from the DRCe versus the Elan 6000. A 1 mL aliquot of the sample is transferred to an auto sampler tube. Nitric acid and 233U (used as an internal standard) are added to the samples and the samples are digested in a microwave oven. The digested samples are diluted to 10 mL with deionized water and the 238U concentration is determined by ICP-MS. The ICP-MS is calibrated with a series of 238U standards. 233U is used as an internal standard to correct for suppression of the signal due to the sample matrix. The Elan 6000 is run in the peakhopping mode with 100 ms dwell times and 50 sweeps. The total integration time is 5, 000 ms. The average of two measurements is used for the determination