An Evaluation of Actinide Reactivity with CO 2 , O 2 , and O 2 /He Gases using Inductively Coupled Plasma Tandem Mass Spectrometry: Application to Simultaneous Measurement of 241 Am/ 241 Pu Ratios in Unseparated Complex Matrices

• Published in: Analytical chemistry (Washington) Vol. 97; no. 23; pp. 12313 - 12320
• Main Authors: Schlieder, Tyler D., Hobbs, Kirby P., French, Amanda D., Hughes, Lee H., Arnquist, Isaac J., Beck, Chelsie
• Format: Journal Article
• Language: English
• Published: United States 17.06.2025
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.5c01397

Accurate actinide measurements are critical within the field of nuclear science. Traditional methods for actinide quantification require time-consuming sample processing prior to analysis. There is a need for rapid analytical techniques that still maintain a high degree of accuracy. In this work, actinide reactivity was assessed for multiple oxygen-containing reaction gases using quadrupole inductively coupled plasma tandem mass spectrometry (Q-ICP-MS/MS) to evaluate actinide analysis in complex sample matrices without analyte-matrix separation. A novel method was developed to measure Am/ Pu in complex sample matrices using an O /He reaction gas with no matrix removal or analyte preconcentration. This inline method reduces matrix-derived polyatomic interferences that complicate traditional ICP-MS analyses by mass-shifting to Am O and Pu O , allowing Am and Pu to be mass separated for simultaneous analysis. While mass shifting is efficient, a small portion of Am (<1.3%) and Pu (<1.4%) react to form AmO and PuO , respectively. Therefore, a mass balance approach was used, in combination with reactivity determined from Pu and Am standard solutions, to correct for residual PuO and AmO . The method was validated by measuring Am/ Pu in Pu isotope standards CRM-136 and CRM-137 (separated in March/April 1970 and February 2022, respectively) in both neat solutions and complex matrices containing diluted soil (NIST SRM 2711a, > 1000 μg·g ). Method detection limits of 15.9 and 9.6 fg·g were determined for Am and Pu, respectively, and Am/ Pu ratios were measured with accuracies within <3.5%. This work presents the first direct analysis of Am/ Pu in unseparated complex matrices, advancing the capabilities for rapid actinide measurements.