High-Throughput Analysis of Additive- Elements and Wear Metals in Lubricants by ICP-OES

Significance of the Topic

Lubricants are essential for reducing friction and wear in machinery across industries. Monitoring wear metals and additive elements in used and unused oils helps predict equipment failure, optimize maintenance, and extend component life. High-throughput, multi-element analysis by ICP-OES provides robust data to support predictive maintenance and quality control.

Objectives and Study Overview

The study aimed to develop a fast, simple, and ASTM D5185-18-compatible method for simultaneous analysis of 22 wear metals and additive elements in lubricants. Using the Agilent 5900 Synchronous Vertical Dual View ICP-OES, integrated AVS 6 switching valve, and an external oil autosampler, the method targeted sample-to-sample throughput under 30 s, including rinse.

Methodology and Instrumentation

Standard and Sample Preparation

• All solutions were prepared by weight-to-weight dilution (1:10) using a cobalt-doped diluent to match viscosities.
• Calibration standards covered 10–90 ppm for most analytes and up to 500 ppm for calcium. A 30 ppm QC check and NIST 1085c oil SRM were included.
• Samples (140 railroad oils) were mixed vigorously and vortexed before analysis.

Použitá instrumentace

• Agilent 5900 SVDV ICP-OES in radial view with SSRF generator, vertical plasma, Cooled Cone Interface, SeaSpray nebulizer, glass cyclonic spray chamber, and 1.4 mm quartz injector torch.
• Integrated AVS 6-port switching valve for rapid sample introduction and reduced gas use.
• Cetac 7400 Oils Homogenizing Autosampler with stirring paddle and drip tray to ensure consistent mixing and prevent cross-contamination.
• ICP Expert Pro software tools: IntelliQuant Screening for rapid semiquantitative scans and Fitted Background Correction for automated background modeling.

Main Results and Discussion

Calibration and Detection

• Excellent linearity (R² > 0.999) for all 22 elements; method detection limits ranged from 0.001 to 0.075 mg/kg.
• Accurate recoveries (92–100%) for wear-metal SRM; precision ≤0.68% RSD.

Control Charts and Trend Analysis

• Three-sigma control charts for calcium and molybdenum in engine oils remained within limits, enabling monitoring of additive depletion.
• IntelliQuant Screening provided full-spectrum heat maps, bar graphs, and pie charts to visualize element profiles in 12 s per sample.

Benefits and Practical Applications

• Throughput of 29 s per sample including rinse supports high-volume laboratories.
• Robust background correction and automated wavelength selection reduce analyst bias and method development time.
• Versatile semiquantitative screening aids in selecting dilutions, calibration ranges, and tracking unexpected contaminants.
• Quantitative data and trend visualization tools support predictive maintenance strategies in rail, automotive, and industrial applications.

Future Trends and Opportunities

Continued integration of smart software and autosampling will drive further productivity gains. Expanding semiquantitative screening to include trace non-metallic contaminants and coupling ICP-OES with machine learning for anomaly detection will enhance predictive maintenance and remote monitoring capabilities. Miniaturized and field-deployable ICP systems may open on-site lubricant analysis for real-time decision support.

Conclusion

The developed method meets ASTM D5185-18 requirements for fast, accurate, and precise multi-element analysis of lubricating oils. Integration of AVS 6 and oil autosampler delivers high throughput and consistent sample handling. IntelliQuant and FBC tools streamline method setup and ensure reliable data, supporting both semiquantitative screening and quantitative monitoring of wear metals and additives.

Reference

1. Introduction to Tribology, The Society of Tribologists and Lubrication Engineers (STLE).
2. Amorin A., Improved Accuracy in the Measurement of Wear Metals and Additives in Lubricant Oils by ICP-OES, Agilent publication 5994-1671EN.
3. ASTM D5185-18, Standard Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by ICP-OES, ASTM International.
4. Reduce Costs and Boost Productivity with the Advanced Valve System (AVS) 6 or 7 Port Switching Valve System, Agilent 5991-6863EN.
5. Agilent IntelliQuant Screening, Agilent publication 5994-1518EN.
6. Fitted Background Correction (FBC) – Fast, Accurate and Fully Automated Background Correction, Agilent 5991-4836EN.