Analysis of Platinum Group Elements (PGEs) in road dust using the Agilent 8900 Triple Quadrupole ICP-MS in MS/MS mode

Significance of the Topic

Monitoring PGEs in the environment is critical due to increased emissions from vehicle catalytic converters, leading to accumulation in road dust and potential ecological impact. Accurate trace-level analysis supports environmental risk assessment and regulatory compliance.

Objectives and Study Overview

This study evaluates the performance of the Agilent 8900 Triple Quadrupole ICP-MS in MS/MS mode using ammonia reaction gas for the quantification of PGEs (Ru, Rh, Pd, Os, Ir, Pt), as well as Au and Ag, in road dust samples. It aims to overcome polyatomic interferences and achieve ng/kg detection limits.

Methodology

• Sample Preparation:
  Microwave-assisted acid digestion of road dust with HNO₃ and HCl, followed by dilution and online addition of internal standards (In, Bi).
• Interference Evaluation:
  Use of synthetic solutions containing typical matrix elements (e.g., Cu, Ni, REEs, Ta, Zr, W) to compare interference removal in No Gas, He and NH₃ modes.
• Calibration and Quality Control:
  External calibration from 0 to 0.5 µg/kg, analysis of certified reference material BCR 723 and four unknown road dust samples.

Instrumentation Used

• Agilent 8900 Triple Quadrupole ICP-MS operating in MS/MS mode
• Standard quartz spray chamber and nebulizer
• Nickel-plated sampler and skimmer cones

Key Results and Discussion

• Detection Limits:
  Below 1 µg/kg for Ru, Rh, Pd, Ag, Au and Pt in NH₃ mode; higher for Ir but still in low ng/kg range.
• Interference Removal:
  NH₃ MS/MS mode achieved near-complete removal of polyatomic interferences (e.g., NiAr on Ru, CuAr on Rh/Pd, ZrO on Ag, TaO on Au), outperforming He mode.
• Recovery from CRM:
  Accurate recoveries for Rh, Pd and Pt (within 100 ± 30 %) in NH₃ mode, versus strong overestimation in No Gas and He modes.
• Analysis of Unknown Samples:
  Reliable quantification of PGEs in four road dust samples under optimum NH₃ conditions, confirming interference-free results and repeatable performance.

Benefits and Practical Applications

The MS/MS approach with ammonia gas offers high sensitivity, low background and robust interference removal, enabling precise quantification of trace PGEs in complex environmental matrices. This method supports environmental monitoring, automotive emission studies and regulatory compliance.

Future Trends and Potential Applications

• Extension to speciation studies and other environmental matrices (e.g., sediments, soils, water).
• Integration with chromatographic separation techniques for comprehensive elemental and molecular analysis.
• Development of standard protocols for routine monitoring in urban and industrial settings.

Conclusion

The Agilent 8900 ICP-QQQ in MS/MS mode with ammonia reaction gas provides a powerful solution for accurate, interference-free determination of PGEs in road dust at ng/kg levels, offering valuable support for environmental assessment and regulatory frameworks.

Reference

• Desprez A., Woods G., Demare D. Analysis of Platinum Group Elements in road dust using the Agilent 8900 Triple Quadrupole ICP-MS in MS/MS mode.