The Measurement of Silicon, Tin, and Titanium in Jet-Engine Oil

Importance of the Topic

The spectrometric analysis of wear metals in jet-engine oils is critical for predictive maintenance and early detection of component failure.
Monitoring elements such as silicon, tin and titanium offers insight into engine health, contamination sources and lubricant degradation before serious damage occurs.

Objectives and Study Overview

This study evaluates the performance of flame and graphite furnace atomic absorption spectroscopy (AAS) for quantifying Si, Sn and Ti in used jet-engine oil.
Key aims include overcoming particle-size limitations of conventional methods and achieving lower detection limits for these infrequently reported elements.

Methodology

Samples of used jet-engine oil were diluted in methyl isobutyl ketone (MIBK) and analyzed by:

• Flame AAS for silicon (nitrous-oxide/acetylene flame, background correction, four-fold dilution)
• Graphite furnace AAS with standard additions calibration for Si, Sn and Ti (nitrogen or argon sheath gas, partitioned graphite tubes)

Careful sampler alignment, burner cleaning and autosampler rinsing protocols minimized carbon buildup and cross-contamination.

Instrumentation Used

• Agilent SpectrAA-40 atomic absorption spectrometer
• Agilent GTA-96 graphite furnace unit with autosampler
• Nitrous oxide-acetylene and argon gases for atomization
• Deuterium background corrector
• MIBK (BDH Analar) solvent and organometallic multielement standards

Main Results and Discussion

Silicon by flame AAS showed linear responses from 2.5 to 50 µg/mL with a characteristic concentration of 1.5 µg/mL.
Graphite furnace AAS achieved characteristic concentrations of 7 pg for Si, 25 pg for Sn and 110 pg for Ti.
Measured concentrations in used oil were approximately 11.6 ppb Si, 0.33 µg/mL Sn and 2.5 µg/mL Ti, all with relative SDs below 7%.
Graphite furnace methods eliminated particle-size bias and increased sensitivity compared to flame AAS.

Benefits and Practical Applications

• Enhanced detection of submicron and larger wear particles
• Significantly lower detection limits for critical elements
• Reduced sample volume and solvent consumption
• Unattended operation for routine monitoring programs
• Early warning of engine component wear and contamination sources

Future Trends and Potential Applications

Integration with ICP-MS and direct solid sampling may further lower detection limits and simplify sample preparation.
Portable spectrometers and real-time on-board oil monitoring systems will enhance field diagnostics.
Advanced chemometric models and AI-driven predictive maintenance algorithms will leverage multielement datasets for condition-based engine management.

Conclusion

The developed flame and graphite furnace AAS protocols afford reliable, high-sensitivity measurement of Si, Sn and Ti in jet-engine oils.
These methods support effective wear-metal monitoring for preventative maintenance and improved engine reliability.

References

1. K.J. Eisentraut, C.S. Saba, R.W. Newman, R.E. Kauffman, W.E. Rhine, “Spectrometric Oil Analysis, Detecting Engine Failures Before They Occur”, Anal. Chem., 56 (1984), pp. 1086A–1094A.
2. T. McKenzie, “Atomic Absorption Spectrophotometry for the Analysis of Wear Metals in Oil Samples”, Varian Instruments at Work, AA-10 (1981).
3. A.D. King, D.R. Hilligoss, G.F. Wallace, “Comparison of Results for Determination of Wear Metals in Used Lubricating Oils by FAAS and ICP-AES”, Atomic Spectroscopy, 5(4) (1984), pp. 189–191.
4. M. de la Guardia, A. Salvador, “Flame AAS Determination of Metals in Lubricating Oils: A Critical Review”, Atomic Spectroscopy, 5(4) (1984), pp. 150–155.
5. C.S. Saba, K.J. Eisentraut, “Determination of Titanium in Aircraft Lubricating Oils by AAS”, Anal. Chem., 49 (1977), pp. 454–457.
6. J.R. Brown, C.S. Saba, W.E. Rhine, K.J. Eisentraut, “Particle Size Independent Spectrometric Determination of Wear Metals in Oils”, Anal. Chem., 52 (1980), pp. 2365–2370.
7. R.E. Kauffman et al., “Quantitative Multielement Determination of Metallic Wear Species in Lubricating Oils”, Anal. Chem., 54 (1984), pp. 975–979.
8. K.J. Eisentraut et al., “Spectrometric Oil Analysis Failures Due to Particle-Size Limitations”, Anal. Chem., 53 (1981), pp. 1099–1103.
9. T. McKenzie, “Safety Practices Using Organic Solvents in Flame AAS”, Varian Instruments at Work, AA-6 (1980).
10. Varian, “Operating Conditions for Flame and Furnace AAS”, Publications No. 85-100274-00 & 85-100504-00 (1981–1983).