Improved throughput for oils analysis by ICP-OES using next generation sample introduction technology

Significance of the Topic

The analysis of wear metals, additives and contaminants in lubricating oils using ICP-OES is vital for predictive maintenance across industries. High sample throughput and stable performance enable timely monitoring of equipment health and cost-effective operations.

Objectives and Study Overview

This study demonstrates an improved method for oil analysis on an Agilent 725 Series radial ICP-OES instrument using the SVS 2 Switching Valve System. The aim is to reduce sample cycle time while maintaining analytical performance.

Methodology and Instrumentation

• Instrument: Agilent 725 Series simultaneous radial ICP-OES with SPS 3 sample preparation and SVS 2 sample introduction.
• Sample introduction: SVS 2 system enables rapid loading of a 0.5 mL sample loop at 500 rpm and injection at 150 rpm.
• Operating conditions: Plasma power 1.35 kW; plasma gas 15 L/min; auxiliary gas 2.25 L/min; concentric SeaSpray nebulizer at 0.55 L/min; radial quartz torch; viewing height 9 mm.
• Calibration: 0–50 mg/L standards in kerosene with viscosity matching; dilution to 10% w/v oil concentration.

Main Results and Discussion

Detection limits for key elements were all below 0.2 mg/L, ensuring sensitivity for wear metal monitoring. Calibration linearity exhibited correlation coefficients above 0.999 for all wavelengths. Sample carryover was negligible, with rinse blank signals below 0.1% of standard. Accuracy and precision were confirmed using NIST SRM 1084a and 1085b, with recoveries within ±10% and RPD below 5%. System stability over six hours showed recoveries within ±10% and RSD under 2%. Crucially, cycle time decreased from approximately 90 s to 33 s per sample, translating to over 100 samples per hour.

Benefits and Practical Applications

• More than doubling of sample throughput reduces analysis time and operational costs.
• Inert sample path and minimal swept volume minimize carryover and contamination.
• High stability and reproducibility support reliable trend analysis for preventive maintenance.

Future Trends and Opportunities

• Further extension of dynamic range via wavelength selection and concentration adjustments for high-content elements.
• Integration of automated dilution and advanced valves for even faster workflows.
• Adoption in other high-throughput laboratories such as environmental and food analysis.

Conclusion

The combination of the SVS 2 sample introduction with the Agilent 725 Series ICP-OES significantly improves throughput without compromising sensitivity, accuracy or stability. This advancement supports efficient and reliable oil condition monitoring.

References

• Hoobin, D. & Vanclay, E. Ultra-fast ICP-OES determinations of soil and plant material using next generation sample introduction technology. Agilent application note SI-02448.
• ASTM D 5185-09, Determination of Additive Elements, Wear-Metals, and Contaminants in Used Lubricating Oils by ICP-AES.
• NIST Standard Reference Materials 1084a and 1085b certificates of analysis.