Lubricating oil analysis according to ASTM D5185 using the Thermo Scientific iCAP 7400 ICP-OES

Importance of the Topic

Lubricant oil analysis by ICP-OES is essential for condition monitoring and preventive maintenance of engines and machinery. It minimizes unscheduled downtime, reduces repair costs, and supports timely maintenance decisions based on wear and contamination indicators.

Objectives and Study Overview

This study demonstrates direct analysis of used lubricating oils following ASTM D5185 to determine additive elements, wear metals, and contaminants. It evaluates the performance of the Thermo Scientific iCAP 7400 ICP-OES Radial system for rapid screening of 22 elements in base and used oils.

Methodology and Instrumentation

Sample Preparation:

• Homogenize oil samples by sonication, pre-heating viscous oils to 60 °C if needed
• Dilute samples and standards by weight in xylene containing 10 mg·kg⁻¹ yttrium as internal standard
• Maintain 10 % oil content in final solutions; prepare blanks and check standards (NIST SRM 1084a) identically

Used Instrumentation:

• Thermo Scientific iCAP 7400 ICP-OES Radial
• Teledyne CETAC ASX-1400 Stirring autosampler
• V-groove nebulizer and baffled cyclonic spray chamber
• Solvent Flex peristaltic pump tubing
• Operating parameters: pump speed 40 rpm; nebulizer gas 0.35 L·min⁻¹; auxiliary gas 1.5 L·min⁻¹; coolant gas 12 L·min⁻¹; RF power 1150 W; radial viewing height 12 mm

Main Results and Discussion

Calibration and check standards showed recoveries within 5 % of certified values, meeting ASTM D5185 accuracy requirements. Analysis of new, intermediate (200 h), and old oil (400 h) revealed:

• Increasing iron levels indicating component wear
• Decreasing magnesium suggesting additive consumption
• Stable silicon implying effective filtration

This trend analysis confirms the method’s sensitivity for monitoring equipment condition.

Benefits and Practical Applications

The direct dilution and aspirate approach eliminates lengthy digestion steps, delivering analysis times under two minutes. High matrix tolerance and reduced interferences enable reliable, high-throughput screening of wear and additive elements in industrial and mobile machinery oils.

Future Trends and Applications

Advances may include portable ICP-OES systems for field diagnostics, automated sample preparation workflows, and enhanced data integration with predictive maintenance platforms. Further refinement of spectral interference correction and miniaturization could expand on-site analytical capabilities.

Conclusion

The Thermo Scientific iCAP 7400 ICP-OES Radial effectively fulfills ASTM D5185 requirements for lubricating oil analysis, offering robust performance, rapid turnaround, and accurate quantification of wear metals, additives, and contaminants.