Optimization of the solvent-based dissolution method to sample volatile organic compound vapors for compound-specific...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Isotope Geochemistry

Background:

• Volatile organic compounds (VOCs) in the gas phase are challenging to analyze using compound-specific isotope analysis (CSIA).
• Previous methods for gas phase VOC sampling had high method detection limits, limiting their application.
• Solvent-based dissolution offers a promising approach for accumulating gaseous VOCs for CSIA.

Purpose of the Study:

• To optimize a solvent-based dissolution method for sampling gas phase VOCs.
• To lower the method detection limits for trichloroethylene (TCE) and benzene.
• To facilitate the application of CSIA to gas phase samples.

Main Methods:

• Optimized a solvent-based dissolution method using tetraethylene glycol dimethyl ether (TGDE) as the solvent.
• Pulled ambient air through TGDE to dissolve and accumulate gaseous VOCs.
• Performed compound-specific isotope analysis (CSIA) on the solvent aliquots.

Main Results:

• Achieved significantly lower method detection limits for TCE (5±1μg/m³) and benzene (1.7±0.5μg/m³) using TGDE compared to previous methods.
• The method detection limit for TCE using δ³⁷Cl analysis was 156±6μg/m³.
• Validated the relationship between gas phase TCE concentration and its accumulation in TGDE, enabling concentration determination.
• Demonstrated the feasibility of field deployment without needing initial gas phase concentration measurements.

Conclusions:

• Tetraethylene glycol dimethyl ether (TGDE) is an effective solvent for capturing TCE and benzene for CSIA.
• The optimized method substantially lowers detection limits for gas phase VOCs.
• This simplified approach enhances the applicability of CSIA for environmental monitoring of gaseous contaminants.