Multi-element Analysis of Used Lubricant Oils

Significance of the Topic

Elemental analysis of lubricating and hydraulic oils is critical for predictive maintenance and quality control in industries relying on engines, turbines, and gear systems. Monitoring wear metals and additive elements helps prevent equipment failure, reduces unplanned downtime, and optimizes lubricant performance.

Study Objectives and Overview

This study evaluates the performance of an Agilent 5110 Radial View ICP-OES equipped with an Easy-fit fully demountable torch and organic-solvent outer tube-set for multi-element analysis of new and used oils. Analysis follows ASTM D5185-18, targeting 22 elements in both used and unused lubricant samples.

Methodology and Instrumentation

The instrument configuration included the Agilent 5110 RV ICP-OES, an SPS 4 autosampler, SeaSpray concentric nebulizer, glass double-pass spray chamber, and the Easy-fit fully demountable torch with a 1.4 mm quartz injector. Calibration standards were prepared in hydrocarbon oil at 5, 10, and 50 ppm; additional high-concentration standards covered P, Ca, Zn, and Mg up to 380 ppm. A cobalt internal standard (25 mg/kg) was introduced online. NIST SRM 1085c was used for method validation. Detection limits and dynamic ranges were established via multi-wavelength selection and the MultiCal feature of the ICP Expert software.

Main Results and Discussion

Recoveries for all 22 elements in the NIST SRM were within ±10 %. Spike-recovery tests on used engine oil (SAE 15W-40), hydraulic oil (SAE 10W), and differential transmission oil (SAE 85W-140) yielded recoveries between 90 % and 108 % across low and high concentration spikes. Method detection limits were below 0.5 mg/kg for all elements, with limits of quantification under 1.4 mg/kg. A 10-hour stability test with repeated analysis of a 5 mg/kg standard demonstrated precision better than 3 % RSD and accuracy within ±10 %, with no injector blockages or outer-tube damage.

Benefits and Practical Applications

• Rapid sample throughput supports high-volume tribology laboratories.
• Fully demountable torch design minimizes maintenance time and cost.
• Wide dynamic range allows single-preparation analysis of trace wear metals and high-level additives.
• Robust performance in organic-solvent matrices reduces downtime from injector fouling.

Future Trends and Potential Applications

• Further automation of torch cleaning and component replacement.
• Integration of data analytics and trend monitoring for real-time lubricant health assessment.
• Extension to additional elements and emerging contaminants in advanced formulations.
• Miniaturized or portable ICP systems for on-site oil analysis in remote locations.

Conclusion

The Agilent 5110 RV ICP-OES with Easy-fit fully demountable torch and organic outer tube-set offers a robust, high-throughput solution for multi-element oil analysis per ASTM D5185-18. The system delivers accurate, precise results across a broad concentration range with minimal maintenance, making it ideal for routine tribology laboratories.

References

• ASTM D5185-18 Standard Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), ASTM International, 2017.