Rapid and Simultaneous Determination of 238Pu, 239Pu, 240Pu, and 241Pu in Samples with High-Level Uranium Using ICP-MS/MS and Extraction Chromatography.

As the most important plutonium isotopes, 238Pu, 239Pu, 240Pu, and 241Pu are normally measured by two to three techniques, which are tedious, time-consuming, and not suitable for rapid analysis in emergency situations. Recently, ICP-MS has become a competitive technique for the rapid measurement of 239Pu, 240Pu, and 241Pu. However, ICP-MS is difficult to measure 238Pu due to the serious isobaric interference of 238U. This work reports a rapid analytical method to solve this problem for the simultaneous determination of 238Pu, 239Pu, 240Pu, and 241Pu using triple-quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) combined with chemical separation. Chemical separation achieved a high decontamination factor of 2.12 × 109 for the most critical interfering element, uranium, by using two sequential TK200 columns. The interferences of 238U1H+ and 238U+ were effectively eliminated by using 12 mL/min He-6 mL/min NH3 as the reaction gases in the octupole collision/reaction cell in ICP-MS/MS. Combined with chemical separation, the overall elimination efficiency of 238U1H+ reached 3.6 × 1017, which is 105 times better than the reported method. With the high 238U+ elimination efficiency of 1.12 × 104 in the ICP-MS/MS measurement, the overall removal efficiency of 238U+ reached 1013, guaranteeing accurate determination of femtogram-level 238Pu as well as 239Pu, 240Pu, and 241Pu in the samples containing milligram-level 238U. The detection time is reduced to minutes, well fulfilling the requirement of rapid analysis. This method is validated by analyzing the standard reference material and the spiked samples.