Reliable Low-Level Analysis of Glycols in Water Using Split Injection

Importance of Topic

Reliable quantification of ethylene glycol and propylene glycol at trace levels in water is crucial because of the high toxicity of ethylene glycol and widespread environmental exposure. Glycols from sources such as antifreeze, aircraft deicing fluids and hydraulic fracturing fluids can contaminate water supplies, making sensitive and reproducible analytical methods essential for environmental monitoring, food safety and industrial quality control.

Objectives and Study Overview

This study aimed to develop and validate a gas chromatographic method using split injection for low-level detection of glycols in aqueous samples. The goals were to overcome challenges associated with splitless injection—such as backflash, poor peak shape and retention time shifts—and to compare the long-term performance of two polyethylene glycol (PEG) columns, Rtx-Wax and Stabilwax, under rigorous water injection conditions.

Methodology and Instrumentation

A 1 µL injection with a 50:1 split ratio into a wool-packed 4 mm inlet liner was employed to minimize water load and eliminate backflash. The GC conditions included a 30 m × 0.53 mm × 1.0 µm PEG column, helium carrier gas at constant flow, an initial oven temperature of 40 °C ramped to 250 °C at 30 °C/min, and FID detection at 250 °C. Calibration standards ranging from 0.5–100 ng on-column were prepared in 10:90 methanol:water with 2-butoxyethanol as internal standard. A lifetime protocol involved cycles of ten splitless water injections followed by one glycol standard injection, repeated until peak symmetry degraded or 600 water injections were reached.

Main Results and Discussion

Split injection delivered sharp, symmetrical peaks and stable retention times for both glycols, while reducing column backflash. On Rtx-Wax columns, linear responses persisted across the calibration range even after 600 water injections, with minimal loss in peak symmetry. One Rtx-Wax column demonstrated robust performance beyond 1,600 water injections. In contrast, Stabilwax columns experienced significant peak symmetry decline after approximately 350 water injections, requiring column trimming. Both column types exhibited low bleed despite high-temperature operation.

Benefits and Practical Applications

The split injection method on Rtx-Wax columns ensures reproducible low-level glycol quantitation by:

• Reducing water vapor load and backflash
• Maintaining consistent peak shape and retention times
• Providing stable performance over hundreds of aqueous injections
• Enabling detection limits suitable for environmental and safety testing

Additional recommendations include thorough syringe rinsing with 50:50 methanol:water between injections to prevent carryover.

Future Trends and Applications

Advancements may focus on further enhancing column chemistries for increased aqueous robustness, integrating automated inlet liners to streamline sample introduction, and extending split injection protocols to other polar contaminants. Coupling with mass spectrometric detection could offer improved specificity and lower detection limits for complex environmental matrices.

Conclusion

The described split injection GC-FID method using an Rtx-Wax column provides reliable, low-level analysis of glycols in water. By minimizing injection port artifacts and maintaining column integrity through extensive water challenge tests, this approach delivers reproducible results essential for environmental monitoring and industrial quality assurance.

Reference

• Laukkonen JD. The history of antifreeze. Crankshift. March 1, 2017.
• Ritter S. What’s that stuff? C&EN. January 1, 2001.
• FracFocus. Chemical disclosure registry: what chemicals are used.