Determination of Ethylene Glycol in Used Engine Oil by Headspace-Gas Chromatography

Importance of the Topic

Detection of ethylene glycol in used engine oil is critical for identifying coolant leakage into the crankcase and predicting engine wear. Traditional colorimetric assays lack sensitivity and objectivity, while direct gas chromatography is hindered by the analyte’s low volatility and polarity. The presented headspace GC method with in-situ derivatization offers improved sensitivity, clean chromatograms, and higher throughput.

Objectives and Overview of the Study

This study aims to develop a simple, rapid, and high-throughput analytical procedure for quantifying ethylene glycol in motor oil. By employing headspace extraction combined with in-situ derivatization, the method seeks to minimize sample preparation steps, avoid column fouling by the oil matrix, and achieve comparable accuracy to established ASTM protocols.

Materials and Methods

Sample Preparation:

• Aliquot 100 µL of used engine oil into a 22 mL headspace vial.
• Add 5 mg of in-situ derivatizing reagent (PerkinElmer Part Number N9301741).
• Seal vial and allow reaction under heated headspace conditions.

Calibration Standards:

• Prepare standards in motor oil ranging from 0.01 % to 0.2 % w/w ethylene glycol.

Used Instrumentation

• Headspace Sampler: PerkinElmer TurboMatrix HS-40 or HS-110.
• Gas Chromatograph: PerkinElmer Clarus 580 GC with split/splitless injector (PPC).
• Detector: Flame Ionization Detector (FID).
• Column: 15 m × 0.32 mm ID × 0.25 µm Elite-5 stationary phase.
• Data System: Waters Empower 3 CDS.

Main Results and Discussion

Under isothermal GC conditions (100 °C), the derivatized ethylene glycol elutes cleanly within a three-minute cycle, enabling injection-to-injection times of less than 3 minutes. The headspace process excludes non-volatile oil components, preventing column contamination. Calibration over 0.01 % to 0.2 % exhibits excellent linearity (R² = 0.997) and precision (3 % RSD). Routine maintenance is limited to replacing headspace o-rings after approximately 2000 injections.

Benefits and Practical Applications of the Method

• Throughput of up to 400 samples per day.
• Minimal sample preparation and reduced operator error.
• Cost per sample under US $ 0.70 (excluding labor and startup).
• Comparable performance to established ASTM methods.

Future Trends and Potential Applications

Expanding the use of headspace derivatization for other polar contaminants in complex matrices can further streamline analytical workflows. Integration with automated sampling platforms and in-field portable GC systems may extend monitoring capabilities in automotive maintenance, quality control, and environmental analysis.

Conclusion

The developed headspace GC method with in-situ derivatization provides a rapid, reliable, and cost-effective solution for detecting ethylene glycol in used engine oil, facilitating early detection of coolant leaks and enhancing laboratory productivity.

References

• ASTM International. ASTM D4291-98 Standard Test Method for Determination of Ethylene Glycol in Used Engine Oil by Gas Chromatography. 1998.
• Ruppel T.D.; Hall G. Determination of Ethylene Glycol in Used Engine Oil by Headspace-Gas Chromatography. PerkinElmer Application Note, 2015.