Solving Doubly Charged Ion Interferences using an Agilent 8900 ICP-QQQ

Importance of the Topic

Spectral interferences in ICP-MS analysis, particularly from doubly charged ions (M++), can lead to inaccurate quantification of trace elements in complex matrices. Addressing these interferences is essential for reliable environmental and industrial testing.

Objectives and Study Overview

This study evaluates the use of an MS/MS oxygen mass-shift method on an Agilent 8900 ICP-QQQ to remove common M++ interferences. Key targets include Ca, Sc, Zn, As, and Se in the presence of Sr, Zr, Ba, and rare earth element spikes.

Methodology

An oxygen reaction cell was used to convert the analyte ions into oxide species (mass shift +16 u), separating them from unreactive M++ interferences. Data were acquired in no-gas, helium KED, and MS/MS O2 mass-shift modes. Background equivalent concentrations (BECs) and recovery in NIST 1640a natural water SRM (spiked and unspiked) were assessed.

Instrumentation

An Agilent 8900 triple quadrupole ICP-MS with a glass concentric nebulizer, quartz double-pass spray chamber, quartz torch (2.5 mm injector), and nickel interface cones was employed. The system operated under standard plasma settings with RF power at 1550 W, defined gas flows, octopole bias, axial acceleration, KED settings, and O2 cell gas flow for MS/MS mode.

Main Results and Discussion

– O2 mass-shift mode achieved the lowest BECs for all analytes, outperforming both no-gas and He modes.
– Helium mode provided acceptable results for unspiked SRM but failed under matrix spikes, showing significant M++ overlap.
– MS/MS O2 mode delivered accurate recoveries (100–106%) for Ca, Sc, Zn, As, and Se in both spiked and unspiked SRM samples.

Benefits and Practical Applications

• Robust removal of doubly charged interferences improves data quality.
• Enables reliable trace-level analysis in complex environmental samples.
• Combines universal KED and targeted reactive modes in one workflow.

Future Trends and Opportunities

• Expansion of reactive gas chemistries (e.g., NH3, H2) for broader interference management.
• Application in food safety, clinical, and industrial monitoring.
• Integration with data analytics and automation for interference prediction and method optimization.

Conclusion

The Agilent 8900 ICP-QQQ with MS/MS O2 mass-shift mode effectively resolves M++ interferences, ensuring accurate quantification of trace elements in challenging matrices. This approach enhances the versatility and reliability of ICP-MS analysis for environmental and industrial applications.

References

1. Agilent Technologies. Reaction data for 70 elements using O2, NH3 and H2 with the Agilent 8800 Triple Quadrupole ICP-MS. Publication 5991-4585EN.
2. Agilent Technologies. Understanding oxygen reaction mode in ICP-MS/MS on the 8800 Triple Quadrupole ICP-MS. Publication 5991-1708EN.