Glycols - Rtx®-Wax

Importance of the topic

Glycols such as propylene glycol and ethylene glycol are widely used as solvents, antifreeze agents and food additives. Accurate quantification of these compounds is critical for quality control in pharmaceutical, food and environmental industries. Gas chromatography provides a robust approach for separating and measuring low-molecular-weight glycols with high specificity and sensitivity.

Objectives and study overview

This application note describes a rapid gas chromatographic method for simultaneous determination of propylene glycol and ethylene glycol in a standard solution. The goals are to achieve clear baseline separation, reproducible retention times and reliable quantitation at 100 µg/mL concentration.

Methodology

A direct injection GC method was optimized on an Rtx®-Wax column (30 m × 0.53 mm ID, 1.0 µm film thickness). The oven program begins at 80 °C (1 min hold), ramps to 120 °C at 8 °C/min, then holds for 3 min. Injection and detector temperatures are set to 220 °C and 270 °C, respectively, using a constant flow of 10psi. A standard solution containing 100 µg/mL of each glycol is injected to evaluate retention behavior and peak shape.

Used instrumentation

• Gas chromatograph equipped with flame ionization detector (FID)
• Rtx®-Wax capillary column, 30 m length, 0.53 mm ID, 1.0 µm film thickness (cat.# 12455)
• Direct splitless injection port
• Data acquisition software for chromatogram integration

Main results and discussion

The method produced sharp, well-resolved peaks for ethylene glycol and propylene glycol within a total run time of under 10 minutes. Retention times were reproducible with variations below 1% RSD. Peak symmetry factors approached unity, indicating minimal column interaction issues. The optimized temperature program balanced peak resolution and analysis speed.

Benefits and practical applications

• Fast analysis suitable for high-throughput QA/QC environments
• High chromatographic resolution reduces risk of coelution
• Simple sample preparation with direct injection
• Applicability to diverse matrices after appropriate extraction

Future trends and potential applications

Advances in capillary column technology and alternative detectors (e.g., mass spectrometry) may further lower detection limits and expand the range of detectable polyols. Coupling GC with automated headspace sampling could enable routine monitoring of residual glycols in pharmaceutical formulations and environmental water samples.

Conclusion

The described GC method on an Rtx®-Wax column facilitates reliable, rapid quantification of propylene glycol and ethylene glycol at trace levels. Its reproducibility and straightforward operation make it an attractive option for laboratories requiring routine glycol analysis.

References

• Restek Corporation. Application note: GC_EV00444 – Glycol analysis on Rtx®-Wax.