Hydrocarbons, C2 – C3, alcohols, C1 - Analysis of low ppm levels of ethylene, propylene and methanol in water

Importance of the Topic

Monitoring trace levels of light hydrocarbons and alcohols in industrial water is critical for process safety and environmental compliance.
Detecting ethylene, propylene and methanol at low parts-per-million concentrations helps identify cooling system leaks and ensures that effluent streams meet regulatory standards before discharge.

Objectives and Overview of the Study

This application note demonstrates a rapid gas chromatographic method for quantifying ethylene, propylene and methanol in aqueous matrices.
The method is designed to support two key operations: weekly leak checks in cooling tower circuits and daily verification of methanol removal from hydrocarbon streams.

Methodology

Samples of water containing target analytes in the range of 8–27 ppm are directly injected into a gas chromatograph.
A temperature-programmed separation enables baseline resolution of ethylene, propylene and methanol within a short analysis window.
Flame ionization detection provides sensitive and reproducible quantitation of each compound.

Used Instrumentation

• Gas chromatograph with wide-bore inlet and flame ionization detector
• Agilent PoraPLOT Q column (0.53 mm × 25 m, 20 µm film thickness)
• Carrier gas: helium at 7 mL/min constant flow
• Temperature program: 35 °C hold 5 min, ramp to 75 °C at 10 °C/min, then to 200 °C at 25 °C/min
• Injection: direct, 0.3 µL water sample, inlet at 100 °C, detector at 250 °C

Main Results and Discussion

The method achieved reliable separation and quantification of ethylene (8.8 ppm), propylene (5.4 ppm) and methanol (27.1 ppm) in aqueous samples.
Retention times were consistent, and peak responses showed excellent linearity across the tested concentration range.
Reproducibility was sufficient for routine process monitoring, with minimal interference from the water matrix.

Practical Benefits and Applications

• Enables early detection of leaks in cooling water systems to prevent equipment damage.
• Supports daily quality control of methanol removal in hydrocarbon processing.
• Offers a straightforward, fast and reliable assay suitable for industrial laboratories.

Future Trends and Potential Uses

Integration of headspace sampling or online monitoring could further streamline analysis and reduce manual handling.
Advances in detector technology and miniaturized chromatography systems may allow field-portable measurements for real-time process surveillance.

Conclusion

This GC-FID method provides a robust and efficient solution for low-ppm analysis of ethylene, propylene and methanol in water.
Its ease of use and reproducibility make it well suited for routine process control and environmental monitoring in petrochemical operations.