TT24-7: Continuous monitoring of trace chemical vapours


The TT24-7 Series 2 is an advanced thermal desorption (TD) system for continuous near-real-time (NRT) monitoring of volatile and semi-volatile organic vapours in air or gas.


With its high-performance analytical capability, reciprocating dual-trapping functionality and cryogen-free operation, the TT24-7 Series 2 is ideal for continuous unattended monitoring, either in static or mobile laboratories.


The TT24-7 Series 2 offers reliable, near-real-time monitoring of chemical warfare agents in military and government installations. It is also an ideal choice for a wide range of challenging civilian applications: advanced environmental research, monitoring pollution levels, controlling air/gas purity, and continuous odour or fragrance profiling.


The TT24-7 Series 2 is normally used in combination with GC or GC/MS technology, but can also be interfaced to direct read-out instrumentation such as process MS systems.

High-performance on-line air/gas monitoring


  • Highly time-resolved data – cycle times as low as 3–5 minutes if required
  • Wide range of sampling flows (up to 800 mL/min) with quantitative trapping offers high sensitivity
  • Dual-trap continuous monitoring – 100% data capture



  • Inert, uniformly-heated flow path offers compatibility for C2–C40 compounds and reactive species
  • Compatible with any make of GC(MS), fast GC, and various real-time vapour detectors
  • Enhanced splitting options to accommodate high-level samples
  • Sampling options include on-line air/gas analysis and tube desorption


Transportable and practical:

  • Small footprint – suitable for mobile laboratories
  • Operates cryogen-free – ideal for unattended remote-site operation over extended periods
  • Robust and low maintenance, including minimal gas consumption
  • Easy to calibrate


Analytical excellence:

  • Efficient desorption means no cross-contamination
  • Ultra-rapid trap desorption also delivers narrow peaks, optimising sensitivity even under splitless analytical conditions; the excellent chromatographic resolution also helps eliminate false positives
  • Great precision, repeatability and linearity
  • Tube desorption option facilitates quantitative repeat analysis for easy validation of analyte recovery

Near-real-time monitoring, 24 hours a day, 7 days a week

Defence and homeland security


The acute toxicity of many chemical warfare agents means that near-real-time (NRT) data is often required to minimise risk to human health. The TT24-7 Series 2 is ideal for continuous unattended monitoring, and a network of systems can all be controlled from a central point.


Relevant application examples include:

  • Monitoring agent stockpiles and destruction facilities
  • On-site monitoring at suspected chemical incidents
  • Counter-terrorism – e.g. routine monitoring of key government buildings and other strategic facilities.

Environmental and workplace air monitoring


The TT24-7 Series 2 excels in situations where the continuous monitoring of VOCs and SVOCs is required over extended periods, including:

  • Priority pollutants in urban air
  • Kinetic studies in atmospheric chemistry
  • Chemical releases from industrial sites or in workplaces
  • Environmental emergency response, including mobile laboratory installations
  • Hazardous chemical processes.

Cleanroom air monitoring


Trace-level airborne contaminants in cleanroom environments can adversely affect the production of silicon wafers and semiconductors, and so are a key application of NRT systems. Tests of these systems often employ isobornyl methacrylate (IBMA), partly because of its use in hard disk drives but also because it breaks down to camphene on chemically active surfaces. Consistency in the amount of camphene arising from multiple analyses of a standard is therefore useful proof of flow path inertness.


Continuous monitoring of odour and fragrance profiles


The TT24-7 Series 2 can also be used for advanced research into emissions from consumer products – for example, to understand the decay profiles of fragrances and other compounds in air fresheners. Conversely, it can also be used to monitor fugitive odorous emissions, to ensure rapid response to industrial incidents.


The TT24-7 Series 2 incorporates two electrically-cooled traps operating in tandem to ensure 100% sample coverage, with no blind spots.


Air is first sampled onto Trap A at flow rates between 50 and 800 mL/min. At the end of the specified time the sampling flow is switched to Trap B, and Trap A is desorbed. Once desorption of Trap A is complete, the process is repeated.


Rapid trap heating rates combined with a reverse flow of carrier gas ensure efficient desorption – giving narrow peaks and optimum sensitivity. In addition, efficient trap cooling after desorption of the sample enables the next stage of sampling to begin with the minimum of delay, making possible cycle times of as little as 3 minutes.

Exceptional performance

Wide analyte range


The TT24-7 Series 2 can be operated at trapping températures down to –30°C and sampling flow rates from 50 to 800 mL/min, making it suitable for a wide range of GC applications.

This flexibility allows quantitative trapping of ultra-volatiles such as C2 hydrocarbons, as well as providing exceptional desorption and recovery characteristics for semi-volatiles.


Designed for remote operation


The TT24-7 Series 2 has been designed with remote operation in mind. Most importantly, no liquid cryogen is required, eliminating the need for topping-up, and facilitating unattended operation for periods of weeks or months.


In addition, the valves and Peltier coolers of the TT24-7 Series 2 use just 100 mL/min of dry air or nitrogen, meaning that a standard 5 ft cylinder lasts at least 2 months. Similarly, carrier gas usage can be minimised – a typical low-split method will use 5–10 mL/min, although this will vary according to analytical conditions.


Compatible with fast GC


When coupled with fast GC, the TT24-7 Series 2 allows short cycle times and rapid near-real-time data generation.


High sensitivity


The TT24-7 Series 2 is compatible with a range of GC/MS systems. However, GC time-of-flight (TOF) mass spectrometers are the ideal partner for monitoring unknowns at optimum sensitivity. The latest TOF systems, such as ALMSCO International’s BenchTOF-dx™, offer full spectral information at typical quadrupole SIM detection levels, and allow the TT24-7 Series 2 to achieve ultra-low detection limits. This enables detection of trace odour compounds and certain chemical warfare agents at ‘general population limit’ (GPL) values.

Advanced technology from Markes International

Markes International pioneered high-performance cryogen-free NRT monitoring with the TT24-7 Series 1 nearly 10 years ago. With its track record of robust, low-maintenance field operation, the TT24-7 Series 1 brought research-grade analysis to the front line of agent monitoring in challenging, out-of-lab environments.


Now the TT24-7 Series 2 builds on the success of its predecessor, offering an advanced feature set that extends the application range. Key enhancements are:

  • Optimised trap cooling for enhanced retention of more volatile compounds
  • Improved serviceability makes trap changes easier
  • Faster cooldown rates allow faster cycle times
  • Inert and uniformly heated inlet line
  • Smaller footprint for mobile laboratories
  • Quantitative tube desorption and re-collection for repeat analysis/validation.

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