Lubricating oil analysis according to ASTM D5185 using the Thermo Scientific iCAP PRO XP ICP-OES

Significance of Oil Analysis

Reliable evaluation of wear metals, contaminants and additive elements in lubricating oils is critical for preventative maintenance of engines and machinery. Early detection of abnormal metal concentrations helps avoid costly unscheduled repairs and downtime by enabling data-driven maintenance scheduling.

Objectives and Study Overview

This study presents an analytical workflow for direct determination of 22 elements in used and base lubricating oils following ASTM D5185. It aims to validate method accuracy and precision using certified reference materials, demonstrate high throughput performance, and highlight strategies to minimize maintenance intervals for the ICP-OES system.

Methodology

Samples and standards were diluted 1:10 (w/w) in a matrix-matched organic solvent containing yttrium as an internal standard. Homogenization was achieved by sonication or gentle heating of viscous oils. Calibration was performed with three levels of oil-based standards and verified using NIST SRM 1085c. An intelligent wavelength selection tool optimized interference-free lines, eliminating the need for mathematical correction factors.

Used Instrumentation

• Thermo Scientific iCAP PRO XP Radial ICP-OES equipped with ceramic D-torch and organic sample introduction kit
• Teledyne CETAC ASX-7400 stirring autosampler under Qtegra ISDS control
• SolventFlex peristaltic pump tubing (orange/white for sample, white/white for drain)
• Baffled glass cyclonic spray chamber and glass V-groove nebulizer
• Auxiliary oxygen or air line to minimize carbon soot deposition

Main Results and Discussion

Analysis of the SRM yielded average recoveries between 96% and 104% for all 20 trace metals, with relative standard deviations below 1%. The method reliably detects wear metals at low mg·kg⁻¹ levels. A single-sample analysis cycle (including uptake, integration and wash) was completed in 67 seconds with three replicates. The built-in air/oxygen purge and removable optics components significantly reduced unscheduled maintenance downtime.

Benefits and Practical Applications

• Direct oil analysis without digestion simplifies sample preparation and decreases turnaround time.
• High matrix tolerance of the radial ICP-OES permits accurate quantification in complex organic matrices.
• Rapid sample throughput (over 50 samples per hour) meets demanding industrial QA/QC needs.
• Integrated gas purge and robust torch design minimize instrument cleaning and maximize uptime.

Future Trends and Possible Applications

Advances in automated sample handling and real-time data analytics are poised to further accelerate oil condition monitoring. Emerging spectroscopic detectors and networked instrumentation will enable remote diagnostics and predictive maintenance across distributed equipment fleets. Coupling oil analysis with machine learning could refine failure-prediction models and optimize lubricant life-cycle management.

Conclusion

The validated ICP-OES procedure conforms to ASTM D5185, delivering accurate, precise and fast quantification of wear metals and additives in lubricating oils. The combination of radial plasma viewing, organic introduction kit and maintenance-reducing features supports high-throughput testing in industrial laboratories.

References

• ASTM D5185 “Standard Test Method for Determination of Additive Elements, Wear Metals, and Contaminants in Used Lubricating Oils and Selected Elements in Base Oils by ICP-OES”
• NIST SRM 1085c “Wear Metals in Lubricating Oil”