WCPS: Reaction Cell Frontier: Analysis of Radionuclides in Environmental Samples using an Innovative Reaction Cell ICP--MSMS

Significance of the topic

Environmental monitoring of long-lived radionuclides such as iodine-129 and plutonium isotopes is critical for assessing nuclear contamination from weapons testing, power plant accidents, and reprocessing emissions. Ultra-trace detection of these isotopes challenges conventional ICP-MS due to polyatomic and isobaric interferences, as well as limited abundance sensitivity.

Objectives and study overview

This study evaluates a novel triple quadrupole ICP-MS (ICP-QQQ) with an advanced collision/reaction cell to improve abundance sensitivity and detection limits for 129I/127I ratios and enable surrogate plutonium analysis in complex matrices. Calibration and validation were performed using NIST SRM 3231 Level I and II standards.

Instrumentation

• Agilent triple quadrupole ICP-MS (ICP-QQQ) equipped with ORS3 collision/reaction cell
• First quadrupole (Q1) for precursor ion selection, second quadrupole (Q2) for product ion filtering
• Reaction gases: high-energy O2 for Xe+ interference removal and NH3 for UH+ suppression
• Spray chamber, ICP torch, dual-stage detector, and turbo molecular pumps ensuring robust operation

Key results and discussion

• Xe+ background was reduced by charge transfer with O2, achieving measured 129I/127I ratios of 0.981×10-6 (Level I) and 0.982×10-8 (Level II), matching certified values within 5% RSD
• Calibration curves for both isotopes demonstrated excellent linearity, supporting external calibration across multiple concentration levels
• Detection limits (3σ, n=10) were 9.6 ng/L for 127I and 0.07 ng/L for 129I, with background equivalent concentration (BEC) for 129I at 0.04 ng/L
• NH3 reaction gas in MS/MS mode suppressed UH+ interferences by over five orders of magnitude, allowing surrogate monitoring of Pu+ analogues (Tl+ and Bi+) in high-matrix samples

Benefits and practical applications

The ICP-QQQ platform delivers superior abundance sensitivity, lower detection limits, and robust interference removal, enabling reliable environmental screening of radionuclides. Its fast analysis time and external calibration streamline routine monitoring in QA/QC and research laboratories.

Future trends and opportunities

Future work will extend ICP-QQQ performance testing to certified radionuclide reference materials and real environmental samples. Potential applications include direct terrestrial and marine sample analysis, coupling with laser ablation, and expansion to other challenging isotopic systems.

Conclusion

The innovative triple quadrupole ICP-QQQ with targeted reaction cell chemistry offers a powerful solution for ultra-trace radionuclide analysis in environmental matrices, overcoming limitations of single quadrupole instruments and complementing alpha spectrometry.

Reference

• Shikamori Y, Nakano K, Sugiyama N, Kakuta S. Reaction Cell Frontier: Analysis of Radionuclides in Environmental Samples using an Innovative Reaction Cell ICP-QQQ. Agilent Technologies Inc., Tokyo, Japan.