Analysis of Platinum Group Elements (PGEs), Silver, and Gold in Roadside Dust using Triple Quadrupole ICP-MS

Significance of the Topic

Monitoring platinum group elements (PGEs), silver and gold in environmental samples has become critical as automotive catalytic converters, industrial processes and consumer electronics release trace levels of these metals into soils and roadside dust. Their persistence and potential impact on ecosystems and human health drives the need for accurate, interference-free analysis at sub-ppb levels.

Objectives and Study Overview

• Develop a robust analytical protocol for low-level determination of Ru, Rh, Pd, Os, Ir, Pt, Ag and Au in complex matrices.
• Evaluate the effectiveness of Agilent 8900 triple quadrupole ICP-MS (ICP-QQQ) with NH₃ reaction gas in MS/MS mode to eliminate spectral interferences.
• Validate method performance using synthetic interference mixtures, spike recovery experiments and a certified reference material (BCR 723 road dust).

Methodology and Instrumentation

The method employs:

• Aqua regia digestion of dust and soil samples to produce high-matrix (≈1 % TDS) solutions.
• Agilent 8900 ICP-QQQ with UHMI aerosol dilution (approximately 4×) to maintain a robust plasma for high total dissolved solids.
• MS/MS mode using Q1 to select analyte masses and NH₃ reaction gas in ORS 4 collision/reaction cell to resolve polyatomic overlaps.
• Comparison of no-gas, He KED (single quad) and NH₃ MS/MS modes to assess interference removal.

Key Results and Discussion

NH₃ MS/MS mode achieved sub-ppt detection limits and Background Equivalent Concentrations (BECs) for all PGEs in complex synthetic matrices, outperforming single-quad and He collision modes by 10^2 to 10^3-fold. Spike recoveries of 1 µg/L in the worst-case matrix mix fell within 90–110 %, and certified values for Rh, Pd and Pt in BCR 723 road dust were reproduced within the 95 % confidence limits.

Benefits and Practical Applications

• Accurate interference-free quantitation of noble metals at ultra-trace levels in environmental monitoring.
• High throughput analysis of high-matrix digests without extensive dilution or chemical cleanup.
• Improved confidence in PGE data for regulatory compliance, pollution source attribution and resource exploration.

Future Trends and Potential Applications

Advances in triple quadrupole ICP-MS and reaction gas chemistries will further expand capabilities for complex sample analysis. Integration with automated sample preparation, on-site monitoring and coupling to separation techniques will broaden applications in geochemistry, mining, wastewater surveillance and emerging fields such as nanoparticle tracking.

Conclusion

The Agilent 8900 ICP-QQQ with NH₃ in MS/MS mode, combined with UHMI aerosol dilution, provides a powerful solution for interference-free, sub-ppb analysis of PGEs, silver and gold in demanding environmental matrices. The method delivers low detection limits, excellent precision and accurate recoveries, making it ideal for routine monitoring and research applications.

References

1. Omrani M., Goriaux M., Liu Y., Martinet S., Jean-Soro L., Ruban V., Environ. Pollut., 257 (2020) 113477.
2. Omrani M., Goriaux M., Jean-Soro L., Ruban V., Environ. Sci. Pollut. Res., 28 (2021) 33231–33240.
3. Agilent Technologies, Handbook of ICP-QQQ Applications using the Agilent 8800 and 8900, 4th Edition (2020).