Improving Throughput for Oils Analysis by ICP-OES

Importance of the Topic

Trend analysis of wear metals in lubricating oils is a cost-effective predictive maintenance tool, enabling early detection of component wear and reducing unplanned downtime. By monitoring element levels, users can identify specific wear mechanisms and schedule maintenance based on actual machine condition rather than fixed intervals.

Objectives and Overview

This study presents an optimized sample introduction system for inductively coupled plasma optical emission spectroscopy (ICP-OES) aimed at improving throughput for oil analysis. The main goal was to reduce sample uptake and washout times while maintaining analytical figures of merit, such as detection limits, linear range, and long-term stability.

Methodology and Instrumentation

The investigation employed an Agilent Vista-PRO radial ICP-OES with a 40 MHz free-running RF generator. A novel dual-tubing arrangement was introduced via a T-piece between the autosampler probe and peristaltic pump, splitting sample flow between the nebulizer and waste line. This “rapid flow” concept doubles sample delivery rate to the pump without overloading the nebulizer. Calibration standards and kerosene diluent were prepared from certified Conostan oil standards.

Used Instrumentation

• Agilent Vista-PRO simultaneous radial ICP-OES
• 3-channel peristaltic pump with modified solvent-flex tubing
• Glass concentric nebulizer with wide bore
• Twister double-pass spray chamber
• AIM 1250 autosampler

Main Results and Discussion

• Sample uptake time decreased from ~24 s to ~15 s using the modified tubing setup.
• Detection limits for most elements in kerosene were below 1 mg/L at a 2 s integration time.
• Maximum measurable concentrations reached up to 2500 mg/L for elements such as Ca, P, and Zn.
• Washout of three orders of magnitude was achieved with a fixed 10 s rinse time, allowing a cycle time of ~47 s per sample.
• An eight-hour continuous run on a 5 mg/L multielement kerosene solution showed signal stability within ±10% and precision better than 2% RSD without recalibration.

Benefits and Practical Applications

• High sample throughput supports busy QA/QC and maintenance laboratories.
• Reliable wear metal trend analysis informs condition-based maintenance decisions.
• Reduced analysis time and reagent consumption lower operating costs.
• Robust radial plasma operation tolerates organic matrices with minimal carbon buildup.

Future Trends and Potential Applications

Further developments may include automated SmartRinse optimization to adjust rinse times dynamically per sample concentration, additional tubing configurations for even faster uptake, and integration with data analytics platforms for real-time maintenance recommendations. Expansion of this approach to other petroleum-based and organic matrices is also anticipated.

Conclusion

The optimized ICP-OES sample introduction system achieves accurate wear metal analysis in under 50 s per sample while preserving low detection limits, wide dynamic range, and long-term stability. This workflow enhances laboratory efficiency and supports predictive maintenance strategies in industrial settings.

References

1. I. Szikla, SmartRinse – the latest advance in maximizing rinse efficiency in ICP-OES analyses.