Air Quality Monitoring

Importance of the topic

The accurate detection of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in ambient air is critical for evaluating environmental and human health risks near industrial or remediation sites. Traditional methods often require separate sampling techniques, extensive solvent use, long preparation and analysis times, and limited analyte ranges. The development of a unified, solvent-free thermal desorption approach addresses industry demands for faster, safer, and more cost-effective air monitoring workflows.

Objectives and overview

This customer study describes the collaboration between a major analytical laboratory and a technology vendor to implement EPA Method TO-17 as a one-step solution for simultaneous analysis of BTEX compounds (benzene, toluene, ethylbenzene, xylenes) and 16 priority polynuclear aromatic hydrocarbons (PAHs) in air samples. Key goals included extending analyte range through innovative sorbent tube design, reducing sample preparation time and solvent hazards, and meeting client requests for improved efficiency and cost savings.

Methodology and instrumentation

A joint research program evaluated new multilayer charcoal-based sorbent tubes paired with an automated thermal desorber and GC/MS system. The approach involved:

• Designing sorbent tubes with sequential weak to strong adsorbent layers to capture analytes from C4 to C40 hydrocarbons without breakthrough or irreversible binding.
• Validating sampling performance metrics such as breakthrough volumes, reporting limits, calibration linearity, precision, recovery, and carryover.
• Testing under 95% relative humidity conditions for up to 50 L of air with plans to expand to 300 L volumes.
• Analyzing real-world field samples to confirm method robustness.

Used Instrumentation

The main instruments and supplies included:

• TurboMatrix 650 ATD automatic thermal desorber with two-stage desorption capability.
• PerkinElmer Clarus SQ8 gas chromatograph-mass spectrometer system.
• Custom multilayer sorbent tubes extending analyte capture range to C40.
• Preset sampling pumps and battery packs enabling extended field sampling without accessory power.

Main results and discussion

The new TO-17 approach demonstrated:

• Efficient simultaneous capture of both light VOCs and heavy SVOCs up to C40 in a single tube.
• Lower detection limits and improved sensitivity compared to EPA Method TO-15 summa canisters.
• Significantly reduced sample preparation time by eliminating solvent extraction and manual tube cleaning.
• Extended sample holding times of approximately 28 days versus seven days under traditional methods.
• Robust performance under high humidity, with optimized dry purging minimizing water vapor interference.

Benefits and practical applications

Adoption of the TO-17 thermal desorption method generated multiple advantages for laboratories and field operations:

• One-step sampling and analysis for both VOCs and SVOCs, reducing the number of media and analytical runs.
• Elimination of toxic organic solvents and associated health and environmental hazards.
• Lower shipping and storage costs due to compact tube design.
• Automated analysis directly from desorption to GC/MS, enabling higher throughput and operator safety.
• Improved cost-effectiveness and faster turnaround for client reporting in environmental monitoring projects.

Future trends and opportunities

Potential developments and applications include:

• Scaling up sampling volumes to enhance detection of ultratrace analytes in challenging matrices.
• Integration with field-deployable thermal desorption systems for on-site analysis.
• Extension of sorbent designs to capture emerging contaminants such as oxygenated organics and higher-molecular-weight pollutants.
• Automation of data processing and instrument calibration to further reduce turnaround time.

Conclusion

The collaborative development of a single-method thermal desorption approach under EPA Method TO-17 has revolutionized air monitoring practices by combining VOC and PAH analysis in one solvent-free workflow. This innovation offers laboratories increased efficiency, lower costs, improved safety, and expanded analyte coverage, setting a new standard for ambient air quality testing.

Reference

1. U.S. Environmental Protection Agency Compendium Method TO-15 Determination of Volatile Organic Compounds in Air Using Summa Canisters and GC/MS Office of Research and Development Cincinnati OH March 1999
2. U.S. Environmental Protection Agency Compendium Method TO-17 Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling on Sorbent Tubes Office of Research and Development Cincinnati OH January 1999
3. U.S. Environmental Protection Agency Compendium Method TO-13A Determination of Polycyclic Aromatic Hydrocarbons in Ambient Air Using GC/MS Office of Research and Development Cincinnati OH March 1999
4. PerkinElmer Clarus SQ8 GC/MS System Product Information
5. Provost R L Marotta L D Single Tube Sampling and Analysis of Volatile and Semi-Volatile Organics in Air Separation Science Webinar
6. Provost R Marotta L Thomas R A Single-Method Approach for Analysis of Volatile and Semi-Volatile Organic Compounds in Air Using Thermal Desorption Coupled with GC-MS LC/GC submission September/October 2014