PLASMA ROBUSTNESS IN ICP-MS BENEFITS OF A LOW CeO/Ce RATIO

Significance of the Topic

The temperature and stability of the plasma in inductively coupled plasma mass spectrometry (ICP-MS) directly influence the accuracy, sensitivity and robustness of elemental analyses. A highly robust plasma, indicated by a low CeO+/Ce+ ratio, more effectively dissociates oxides and the sample matrix, enabling reliable measurements of samples with high dissolved solid content.

Objectives and Overview

This whitepaper presents the performance characteristics of the Agilent 7800 Quadrupole ICP-MS, with emphasis on its exceptionally low CeO/Ce ratio and integrated High Matrix Introduction (HMI) technology. The goals are to demonstrate:

• The native plasma robustness of the 7800 ICP-MS.
• The enhancement in matrix tolerance achieved with HMI.
• The impact on sensitivity and recovery for challenging elements such as cadmium.

Methodology and Instrumentation

The study employs the Agilent 7800 Quadrupole ICP-MS equipped with:

• A high-efficiency radio-frequency (RF) generator operating at 27.12 MHz.
• An optimized ICP torch with a tailored injector internal diameter to support stable plasma conditions.
• High Matrix Introduction (HMI) sample introduction system for intelligent aerosol dilution and reduced water vapor loading.

Key metrics include measurement of the CeO+/Ce+ ratio to assess plasma robustness and evaluation of cadmium spike recoveries across varying total dissolved solids (TDS) levels.

Main Results and Discussion

Native operation of the 7800 ICP-MS yields a CeO/Ce ratio below 1%, the lowest among comparable instruments, permitting routine analysis of samples with TDS up to 2 000 ppm.

Implementation of HMI further reduces the CeO/Ce ratio to approximately 0.2% and extends matrix tolerance by a factor of five. Figure 1 data illustrate that higher plasma temperatures (around 7 800 K) achieve >80% ionization for elements like cadmium, compared to <5% at lower temperatures (5 800 K).

Cadmium spike recovery experiments (Figure 2) in salt matrices up to 3% TDS demonstrate:

• Typical non-HMI systems (CeO/Ce ~2.5%) yield only 16% recovery at 3% TDS.
• The 7800 ICP-MS at 1% CeO/Ce achieves improved but variable recovery.
• With HMI, cadmium recovery remains near 100% across all tested TDS levels, eliminating the need for matrix-matched calibration standards.

Benefits and Practical Applications

• Enhanced matrix tolerance allows direct analysis of high-salt or high-TDS samples without extensive sample preparation.
• Reduced oxide and polyatomic interferences improve detection limits for poorly ionized elements.
• Stable, low-maintenance operation supports high throughput in routine and quality-control laboratories.
• Consistent analytical performance simplifies calibration and increases data reliability.

Future Trends and Applications

Emerging developments may include:

• Further automation of plasma optimization using real-time feedback and machine learning algorithms.
• Integration of advanced sample introduction systems for even higher matrix loads.
• Extension of robust plasma technology to tandem mass spectrometry and hyphenated techniques for complex speciation studies.
• Broader adoption in industrial process monitoring, environmental testing and bioanalytical workflows.

Conclusion

The Agilent 7800 Quadrupole ICP-MS, particularly when fitted with HMI, sets a new standard for plasma robustness and matrix tolerance in ICP-MS analysis. Its exceptionally low CeO/Ce ratio supports accurate, interference-free measurements of high-TDS samples, streamlining workflows and improving data quality in diverse analytical applications.

References

No formal literature references were provided in the source document.