EPA Method 502.2 Drinking Water

Significance of the Topic

Gas chromatography with cyanopropyl phenyl methylpolysiloxane capillary columns plays a vital role in environmental monitoring by enabling sensitive separation and quantification of volatile organic compounds in air and water samples.

Objectives and Study Overview

This application note evaluates the performance of a 75 m × 0.53 mm I.D. × 2.5 µm cyanopropyl phenyl methylpolysiloxane column (007-502) for trapping, separating and analyzing 60 priority pollutants in drinking and environmental water matrices.

Methodology and Instrumentation Used

Sample Collection and Trapping

• Tenax/Silica/Charcoal trap for preconcentration of volatiles
• 11 min purge to remove moisture and bulk air

Chromatographic Conditions

• Column: 007-502 cyanopropyl phenyl methylpolysiloxane, 75 m × 0.53 mm I.D., 2.5 µm film
• Temperature Program: 35 °C (10 min hold), ramp 4 °C/min to 280 °C (5 min hold)
• Carrier Gas: Helium at 10 mL/min

Detection and Analysis

Main Results and Discussion

The method achieved baseline separation of 60 compounds spanning light halogenated methanes, olefins, chlorinated ethanes and ethenes, aromatic hydrocarbons and polychlorinated species. Key observations include:

• Early eluters (dichlorofluoromethane to trichlorofluoromethane) displayed sharp peaks with retention times under 8 min.
• Aromatic region (benzene to naphthalene) was well resolved, enabling clear identification of isomers such as o-, m-, p-xylene.
• Later eluters (hexachlorobutadiene, 1,2,3-trichlorobenzene) eluted between 50 min and 60 min without coelution.

Chromatographic performance demonstrates the column’s balanced polarity for both polar halogenated species and nonpolar aromatics.

Benefits and Practical Applications

This method supports stringent regulatory compliance for drinking water and ambient air quality by:

• Providing a single-run analysis of diverse VOCs
• Reducing sample handling through on-line trapping
• Ensuring reproducible retention times and peak shapes for trace-level detection

Future Trends and Applications

Advances may include faster temperature programming, integration with tandem mass spectrometry for enhanced selectivity, miniaturized portable GC systems for field analysis, and data processing aided by machine-learning algorithms for automated compound identification.

Conclusion

The 007-502 cyanopropyl phenyl methylpolysiloxane column offers robust, high-resolution separation of a broad spectrum of environmental VOCs. The described trapping and GC protocol delivers reliable, regulatory-compliant analysis for environmental and drinking water monitoring.

References

EPA Method 502.2 Application Note, Quadrex Corporation, GC Capillary Column 007-502 Series.