Analysis of wear metals and contaminants in engine oils using the 4100 MP-AES

Significance of the topic

Monitoring the elemental composition of engine oils is essential for preventive maintenance. Tracking wear metals such as copper, iron and aluminum reveals mechanical degradation, while elements like sodium and silicon signal contamination by coolant or road dust. Timely analysis helps to prevent unexpected failures, extend equipment life and reduce maintenance costs.

Objectives and study overview

This work evaluates the Agilent 4100 MP-AES for routine multi-element determination of wear and contaminant metals in used engine oils. Key aims include assessing accuracy against certified reference materials, determining spike recoveries in mixed gear oils, comparing sample throughput to conventional flame AA methods and examining long-term analytical stability.

Methodology

Oil samples and standards were prepared by diluting with an organic solvent (Shellsol) to match matrix conditions. Calibration standards ranged from 5 ppm to 50 ppm using an oil-based multi-element standard. A NIST SRM 1085b reference was analyzed after 1:10 dilution. Spiked used gear oils were prepared at 10.2 ppm for validation. Analysis employed fast sequential atomic emission spectroscopy using nitrogen plasma.

Used instrumentation

• Agilent 4100 MP-AES with magnetically coupled microwave plasma
• External Gas Control Module for air injection to reduce carbon deposition
• OneNeb inert nebulizer and double-pass glass cyclonic spray chamber
• Agilent SPS 3 Sample Preparation System for automated delivery

Key results and discussion

Analysis of SRM 1085b showed recoveries between 96 % and 104 % for major elements. Spike recovery in mixed gear oil ranged from 92 % to 109 %, demonstrating method validity. Calibration curves exhibited excellent linearity (r² > 0.99998) and sensitivity, exemplified by the Cu 327.395 nm signal. Automated sampling delivered under 5 minutes per sample (~13 samples per hour). Long-term precision over 8 hours yielded RSDs below 1 % for key elements.

Benefits and practical applications

• High sample throughput with unattended operation
• Reduced operating costs versus flame AA and no flammable gases
• Robust performance for organic matrices
• Accurate trend monitoring for predictive maintenance

Future trends and potential applications

Integration of MP-AES with remote monitoring platforms could enable real-time lubricant health assessment. Further expansion to biofuels, hydraulic fluids and other industrial oils is anticipated. Advances in automation and data analytics will strengthen predictive maintenance strategies.

Conclusion

The Agilent 4100 MP-AES, equipped with EGCM and OneNeb nebulizer, provides a reliable, cost-effective and safe solution for multi-element wear metal analysis in engine oils. It offers superior throughput, precision and minimal solvent interference, making it well suited for high-volume laboratories.

References

• J. Moffett and G. Russell, Evaluation of a novel nebulizer using an inductively coupled plasma optical emission spectrometer, Agilent Application Note 5990-8340EN.