Glycols on Rtx®-BAC Plus 1 and 2 Column Set

Significance of the Topic

Glycols such as ethylene glycol, propylene glycol, 1,3-propanediol and diethylene glycol are key components in food, pharmaceutical, antifreeze and industrial formulations. Their precise analysis is critical for quality assurance, regulatory compliance and process optimization. Gas chromatography on specialized polar columns provides fast, reproducible separation and accurate quantification of these compounds.

Objectives and Study Overview

This application note evaluates the retention behavior and separation efficiency of four glycols on two related polar stationary phases, Rtx®-BAC Plus 1 and BAC Plus 2. The comparative study focuses on retention time shifts and chromatographic performance under identical conditions.

Methodology

Sample Preparation:

• Diluent: methanol:water (40:60)
• Concentration: 200 µg/mL each glycol

Injection Conditions:

• Volume: 1 µL (split ratio 20:1)
• Inlet temperature: 260 °C
• Liner: 4 mm straight inlet with wool

Oven Program:

• Initial temperature: 60 °C (0 min hold)
• Ramp: to 240 °C at 20 °C/min
• Final hold: 5 min

Carrier and Detection:

• Carrier gas: helium, constant flow (70 cm/s)
• Detector: FID at 240 °C
• Make-up gas: nitrogen at 30 mL/min

Used Instrumentation

Gas chromatograph: Agilent/HP 6890 GC configured with two columns connected via a 5 m guard column and a Universal “Y” Press-Tight® connector.

• Rtx®-BAC Plus 1, 30 m × 0.32 mm ID, 1.8 µm
• Rtx®-BAC Plus 2, 30 m × 0.32 mm ID, 0.6 µm

Manual injections performed with a Merlin Microshot injector.

Main Results and Discussion

Baseline separation of all four glycols was achieved on both columns. Observed retention times (min) were:

• Ethylene glycol: 1.98 (Plus 1) vs. 2.21 (Plus 2)
• Propylene glycol: 2.32 vs. 2.43
• 1,3-Propanediol: 3.04 vs. 3.28
• Diethylene glycol: 4.38 vs. 4.39

The BAC Plus 2 phase exhibited slightly increased retention for lower-boiling glycols, attributable to its thinner film thickness. Both columns delivered sharp peaks and excellent resolution, supporting reliable quantitation.

Benefits and Practical Applications

The described method allows rapid, reproducible glycol profiling with minimal sample preparation. Key applications include:

• Quality control in pharmaceutical and food production
• Analysis of antifreeze and lubricant formulations
• Environmental monitoring of polar organic contaminants

Future Trends and Potential Applications

Upcoming developments may involve coupling these polar phases to mass spectrometry for enhanced selectivity, deploying shorter or narrower-bore columns for higher throughput, and integrating into two-dimensional GC workflows for more complex sample matrices. Portable GC systems could enable on-site glycol screening in industrial environments.

Conclusion

Both Rtx®-BAC Plus 1 and Plus 2 columns provide efficient, reproducible separation of common glycols. Selection between them can be based on desired retention time and throughput, with Plus 2 offering slightly longer retention for low-boiling analytes. This robust GC-FID method is well suited to diverse analytical challenges in research, QA/QC and process monitoring.