Analysis of Ethylene Glycol in Wastewater by Direct Aqueous Injection

Significance of the Topic

Monitoring ethylene glycol in industrial and municipal wastewater is critical to prevent environmental damage. Elevated glycol levels increase Biological Oxygen Demand, leading to oxygen depletion and harm to aquatic ecosystems. Furthermore, ethylene glycol poses direct health risks in case of human or wildlife exposure. A rapid, reliable analytical method supports quality control at disposal sites and helps safeguard water resources.

Objectives and Overview of the Study

This study aims to develop and validate a direct aqueous injection gas chromatography method with flame ionization detection (GC-FID) for quantifying ethylene glycol in wastewater. The approach avoids derivatization, minimizes sample preparation, and demonstrates linearity, precision, and sensitivity suitable for routine monitoring.

Instrumentation

• Optic 3 programmable injector
• Focus robotic sample processor
• Agilent 5890 GC with flame ionization detector (FID)
• SGE SolGel Wax capillary column (30 m × 0.25 mm i.d. × 0.25 µm)

Methodology

Calibration standards were prepared by diluting ethylene glycol in HPLC-grade water over a concentration range of 1–100 ppm. A 2 µL cold split injection was applied under the following conditions:

• Injector temperature program: initial 60 °C, ramped at 16 °C/s to 250 °C
• Carrier gas: helium at constant flow 2.3 mL/min
• Oven temperature program: 100 °C (2 min), then 10 °C/min to 230 °C
• FID settings: 250 °C, hydrogen flow 40 mL/min, air flow 400 mL/min

Main Results and Discussion

The calibration curve demonstrated excellent linearity (r = 0.9997) across the 1–100 ppm range. Repeatability tests on wastewater samples yielded a mean peak area of 201 030 counts with a standard deviation of 3 964 and %RSD of 1.97%, confirming robust precision. Maintaining the injector hot during sample introduction prevented water condensation on the column, ensuring sharp, symmetric peaks for ethylene glycol and co-eluting diethylene glycol.

Benefits and Practical Application

• No derivatization or extensive sample cleanup required
• Fast throughput with a 2-minute transfer time
• High sensitivity suitable for trace-level detection
• Potential for integration into online monitoring platforms using the Focus Flowcell for automated, real-time analysis

Future Trends and Opportunities

Advancements may include expanding the method to other glycols such as propylene glycol and diethylene glycol. Coupling the Optic 3 injector to continuous flow systems can enable real-time discharge monitoring. Integration with data analytics and remote reporting could further enhance regulatory compliance and environmental protection.

Conclusion

The direct aqueous injection GC-FID method offers a rapid, accurate, and reproducible protocol for ethylene glycol quantification in wastewater. Its simplicity and potential for automation make it well-suited for routine monitoring in environmental and industrial laboratories.

References

(1) New Jersey Department of Health and Senior Services, Hazardous Substances Data Sheet