Breathe Easier - Thermal desorption systems

Importance of the topic

Thermal desorption is a critical technique for environmental health and safety monitoring, enabling sensitive detection of volatile and semivolatile organic compounds in air. By concentrating trace analytes onto sorbent traps and releasing them in a controlled manner, thermal desorption systems support compliance with regulatory standards and provide reliable data for air quality assessment.

Study objectives and overview

This whitepaper describes the collaboration between Agilent and Markes International to deliver an integrated solution based on the UNITY thermal desorber, ULTRA autosampler, SecureTD re-collection, and Air Server on-line sampling modules. The aim is to demonstrate system versatility for routine and challenging air analysis applications, from ultra-volatile compounds to high-boiling pesticides.

Methodology and used instrumentation

The core of the system is the UNITY single-tube thermal desorber featuring an electrically cooled focusing trap with rapid heating (>60 °C/s), inert flow paths, and secure O-ring seals. Key modules and options include:

• ULTRA multi-tube autosampler: automates up to 100 sorbent tubes with patented DiffLok™ sealing caps
• SecureTD re-collection accessory: captures backup sample for method validation and repeat analysis
• Air Server: direct introduction of canister or on-line air samples into the focusing trap
• Optional electronic mass flow control (MFC) for precise split flow management
• Internal standard/dry purge (ISDP) module: adds gas-phase standards and removes water
• Permeable membrane dryers for on-line moisture reduction

Key results and discussion

Performance evaluations demonstrated:

• Efficient retention of ultra-volatile analytes (ethyne, acetylene) without liquid cryogen
• Complete desorption of high-boiling pesticides and 6-ring PAHs with no carryover
• Stable, inert chromatography of sticky and reactive compounds (amines, thiols, organophosphates)
• Splitless and split operation for trace-level and high-concentration samples with high-resolution GC peaks
• SecureTD re-collection yielding reproducible chromatograms for method validation
• ULTRA autosampler reliability over extended periods using DiffLok caps
• Direct Air Server sampling of ozone precursors, air toxics, and volatile sulphur compounds with detection limits down to tens of parts per trillion

Benefits and practical applications

The integrated system meets stringent requirements of US EPA TO-17, TO-14/15, ASTM D6196, ISO 16017, NIOSH 2549 and UK HSE methods. It supports:

• Ambient monitoring of ozone precursors (C2–C10 hydrocarbons)
• Air toxics screening for volatile organic compounds in canisters
• Continuous on-line surveillance of odorous sulfur species
• Quality assurance via re-collection and internal standard checks
• Flexible sample introduction for bags, canisters or direct gas streams

Future trends and opportunities

Emerging developments include miniaturized TD modules for field deployment, real-time coupling with mass spectrometry and IMS, AI-driven sequence optimization, and expanded use of permeable membranes for humidity control. Integration with networked monitoring platforms and automated data analytics promises enhanced spatial and temporal resolution of air quality assessments.

Conclusion

The Agilent-Markes thermal desorption platform offers a comprehensive, compliant, and highly flexible solution for air analysis. Modular autosamplers, robust instrument design, and advanced sampling accessories enable precise quantitation of a broad volatility range. SecureTD and Air Server options further enhance data confidence and continuous monitoring capabilities.

Reference

• Agilent Technologies and Markes International technical brochure, 2003.