Improved Performance And Dynamic Range For EPA Method TO-15 using the Entech 7200 and Agilent 7890B/5977 GCMS

Significance of the Topic

Volatile organic compound analysis in air at trace levels is critical for environmental monitoring and regulatory compliance. EPA Method TO-15 is widely used to detect VOCs in canister collected air samples. Achieving low parts per trillion detection limits and a broad dynamic range improves laboratory productivity and accuracy.

Objectives and Overview of the Study

The application note presents enhancements to the EPA TO-15 protocol using the Entech 7200 preconcentrator coupled with the Agilent 7890B5977 GCMS. The goal is to expand dynamic range, improve linearity, sensitivity, and reduce sample carryover for routine and high concentration air analyses.

Methodology and Instrumentation

The study employs an extended cold trap dehydration technique with a three stage trapping sequence. An empty silonite coated trap at minus forty degrees Celsius removes water, followed by a Tenax trap at minus forty degrees Celsius for VOC capture, and final focusing on an ultra low volume trap. Entech Accu Sample technology integrates electronic volume control, digital rotary valve actuation, and fully silonite treated transfer lines. GC conditions include a temperature program starting at thirty five degrees Celsius.

Used Instrumentation

• Entech 7200 Preconcentrator with extended cold trap dehydration
• Agilent 7890B gas chromatograph
• Agilent 5977 mass spectrometer in full scan electron ionization mode
• Entech 7650 or 7016D autosampler for sample isolation

Main Results and Discussion

Calibration over a 1000 fold range from forty parts per trillion to forty parts per billion showed relative standard deviations below thirty percent, exceeding TO-15 criteria. The Agilent MS demonstrated linear response across three orders of magnitude. Method detection limits below fifty parts per trillion were achieved for most compounds. Water removal at minus forty degrees Celsius prevented loss of polar VOCs and reduced carryover, enabling rapid recovery after high concentration samples.

Benefits and Practical Applications of the Method

• Expanded dynamic range reduces the need for multiple dilutions
• Low detection limits improve sensitivity for trace analysis
• Enhanced inertness minimizes sample loss and carryover
• Robotic autosampler compatibility increases throughput
• Comprehensive volume measurement ensures reproducible results

Future Trends and Possibilities for Use

Continued development of ultra inert surface coatings and advanced cooling techniques may further lower detection limits. Integration with automated dilution and sample handling systems will enhance productivity in air quality monitoring, soil gas surveys, and vapor intrusion studies. Emerging applications could include real time monitoring of additional trace gases such as carbon dioxide isotopologues and light hydrocarbons.

Conclusion

The combination of the Entech 7200 preconcentrator and Agilent 7890B5977 GCMS delivers significant improvements in sensitivity, linearity, and dynamic range for VOC analysis under EPA Method TO-15. The extended cold trap dehydration approach and Accu Sample technology ensure reliable trace level detection and rapid recovery from high concentration samples, supporting high throughput environmental monitoring laboratories.