Determination of plutonium concentrations and isotope ratios in environmental samples with a double-focusing sector field ICP-MS

An analytical method for the ultratrace and isotopic analysis of plutonium in sediment samples using a double focusing sector field ICP mass spectrome ter (ICP-SMS) is described. A detection limit for plutonium in the sub-fg m l(-1) range was achieved. The ICP-S MS results were in acceptable agreement with alpha spectrometry. At the low fg ml(-1) level a precision in isotope ratio measurements of 2-10% RSD was achieved. Accuracy of the results was assessed by U-238/U-235 and Tl-205/Tl-203 isotope ratio determinations usin g isotopic standards and a natural Tl standard solution, respectively. It w as shown that correction for (UH+)-U-238 and (UH2+)-U-238 is necessary for both plutonium concentration and isotopic composition determinations, From a practical standpoint, the use of ICP-SMS for plutonium measurements is an attractive alternative to techniques such as alpha spectrometry and therma l ionization mass spectrometry (TIMS) due to its higher throughput and abil ity to measure both concentration and isotopic ratio on the same sample. (C ) 1999 Elsevier Science B.V. All rights reserved.