The ultratrace determination of iodine 129 using the Agilent 8800 Triple Quadrupole ICP-MS in MS/MS mode

Importance of the Topic

Iodine-129 is a long-lived radionuclide released by nuclear activities and poses challenges for environmental monitoring due to its extremely low concentration and isobaric interference from xenon. Ultra-trace determination of 129I and accurate measurement of the 129I/127I ratio are critical for nuclear forensics, environmental safety and regulatory compliance. High sensitivity and low background are essential to overcome spectral overlap and detect 129I at parts-per-trillion levels.

Objectives and Study Overview

This work evaluates the performance of the Agilent 8800 Triple Quadrupole ICP-MS in MS/MS mode for 129I analysis. Goals include:

• Eliminating 129Xe interference via an oxygen reaction cell
• Improving detection limits for 129I compared to single-quadrupole ICP-MS
• Achieving precise 129I/127I ratio measurements in certified NIST standards

Methodology and Instrumentation

A dedicated MS/MS setup was used:

• Instrument: Agilent 8800 Triple Quadrupole ICP-MS
• Sample introduction: glass concentric nebulizer, Peltier-cooled quartz double-pass spray chamber, one-piece quartz torch with 2.5 mm injector
• Operating conditions: 1550 W RF power, 8 mm sampling depth, 1.05 L/min carrier gas, 2 °C spray chamber, O2 reaction gas at 0.7 mL/min
• Mass filtering: Q1 set to pass only m/z 127 and 129 into ORS3 cell; Q2 isolates target analytes after reaction
• Calibration: Dilutions of NIST SRM 3231 Level I and II in 0.5 % TMAH; blank matrix from potassium iodide

Main Results and Discussion

Oxygen reaction mode removed 129Xe+ interference by charge transfer, converting Xe+ to neutral Xe and yielding background-level signal at m/z 129. MS/MS filtering reduced mass tailing and achieved an abundance sensitivity better than 10-10. Calibration plots for 127I (ppb range) and 129I (ppt range) were linear with R2 ≈ 1. Detection limits (3σ, n=10):

• 127I: 0.26 µg/L (BEC 2.97 µg/L)
• 129I: 0.07 ng/L (BEC 0.04 ng/L)

Measured 129I/127I ratios in NIST 3231 Level I (0.981×10-6 certified) and Level II (0.982×10-8) agreed within uncertainty, with RSD below 5 % for Level I and below 8 % for Level II. Detection limits for 129I improved by ~15-fold over previous single-quadruple ICP-MS.

Benefits and Practical Applications

This MS/MS approach offers:

• High throughput with minimal sample preparation
• Sensitivity to ppt-level 129I and precise isotopic ratios
• Robust interference removal across sample types
• Potential use in environmental surveillance, nuclear forensics, high-purity metal analysis, clinical studies and petrochemical QA/QC

Future Trends and Potential Applications

Advancements may include exploration of alternative reaction gases to target other interferences, integration with separation techniques for speciation, and automated sampling for high sample loads. Expansion to other radionuclides, routine monitoring of nuclear facilities, and coupling with chromatography for complex matrices will further extend the utility of triple-quad ICP-MS in analytical chemistry.

Conclusion

The Agilent 8800 ICP-QQQ in MS/MS mode delivers exceptional abundance sensitivity, low background and accurate ultratrace determination of 129I. It outperforms previous single-quad ICP-MS and opens new analytical opportunities for radionuclide and isotopic ratio measurements.

References

Shikamori Y, Nakano K, Sugiyama N, Kakuta S. The ultratrace determination of iodine-129 in aqueous samples using the Agilent 7700x ICP-MS with oxygen reaction mode. Agilent Technologies Publication 5990-8171EN; 2011.
Shikamori Y, Nakano K, Sugiyama N, Kakuta S. The ultratrace determination of iodine-129 using the Agilent 8800 Triple Quadrupole ICP-MS in MS/MS mode. Agilent Technologies Application Note; 2012.