Single Nanoparticle Analysis of Asphaltene Solutions using ICP-QQQ

Importance of the Topic

Asphaltene aggregates in heavy petroleum fractions can deposit in refining equipment, causing operational issues. Detailed characterization of metal nanoparticles (NPs) and dissolved metals in asphaltenes enhances understanding of their behavior and supports the oil, petrochemical, and semiconductor industries.

Objectives and Study Overview

This study employs spICP-MS with a triple quadrupole ICP-MS (Agilent 8900 ICP-QQQ) and MassHunter Single Nanoparticle software to:

• Discriminate nanoparticulate and dissolved metal species in asphaltene solutions.
• Quantify and size-characterize Fe and Mo NPs in three distinct asphaltene samples.
• Compare total metal concentrations obtained by spICP-MS, direct dilution, and wet acid digestion.

Methodology and Instrumentation

Sample Preparation:

• Three asphaltene sources (heavy Mexican crude, pump deposit, oxidized asphalt) extracted with n-heptane at 80 °C and filtered.
• Dilution in o-xylene (1:2100–1:2700) to prevent NP agglomeration.
• Calibration standards (1–1000 μg/kg) from organometallic mixtures; Sc and Y internal standards.
• 60 nm Ag NP reference to determine nebulization efficiency (6.5%).
• Wet acid digestion (H₂SO₄, HCl, HNO₃) for total metal analysis.

Instrumentation:

• Agilent 8900 Triple Quadrupole ICP-MS with quartz nebulizer and spray chamber; organic torch and O₂ addition for hydrocarbon matrices.
• MS/MS mode with He cell gas for interference removal; fast Time Resolved Analysis (0.1 ms dwell).

Key Results and Discussion

NP Detection and Size Distribution:

• Discrete pulses for Fe and Mo confirmed NP presence; V and Ni showed continuous signals as dissolved species.
• Assumed Fe₂O₃ and MoS₂ compositions yielded average NP sizes: Fe varied by sample; Mo consistently 70–80 nm.

Concentration Comparison:

• spICP-MS and acid digestion produced similar total Fe; direct dilution underestimated Fe due to incomplete ionization of larger particles.
• Mo totals by spICP-MS matched acid digestion in one sample but diverged in others, indicating calibration and matrix effects require further study.

Benefits and Practical Applications

spICP-MS with ICP-QQQ offers:

• Simultaneous quantification of nanoparticulate and dissolved metals in complex hydrocarbon media.
• High sensitivity and interference control essential for petroleum and solvent analyses.
• Streamlined data acquisition and reporting via specialized software.

Future Trends and Opportunities

Emerging directions include:

• Extending the method to additional petroleum fractions and organic solvents used in semiconductor manufacturing.
• Optimizing calibration and digestion protocols to improve Mo quantification consistency.
• Integrating routine spICP-MS NP characterization into QA/QC workflows in the energy and chemical sectors.

Conclusion

The application of spICP-MS on Agilent 8900 ICP-QQQ effectively differentiates and quantifies metal NPs and dissolved metals within asphaltenes. Its high sensitivity, robust interference removal, and dedicated software support enable reliable analysis of complex hydrocarbon matrices, with broad industrial relevance.

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