Thermal Desorption Systems for Environmental & Workplace Air Monitoring

Environmental and occupational health & safety (EH&S) applications include:

• Workplace air monitoring - occupational hygiene: personal exposure assessment, biological exposure measurement and general monitoring of workplace atmospheres. 
  
• Indoor air – homes, schools, offices, hospitals, etc. Involves air monitoring, materials emissions testing of construction products and tests of ventilation. 
  
• Ambient air – urban or rural. Includes: biogenic and anthropogenic emissions, measurement of average urban pollution levels (e.g. ‘ozone precursors’) and rural ‘background’ pollution assessment. 
  
• Stationary source emissions – industrial stacks, landfill emissions and associated industrial odour issues/ fence-line monitoring.

Automatic Thermal Desorption Systems: ULTRA-UNITY, ULTRA 50:50 & AutoSecure TD

Whether your interest is in trace-level (sub-ppt) measurements of stratospheric pollution or high concentration stack emissions Markes thermal desorption systems have the flexibility to produce reliable, quantitative data.  UNITY is a cryogen-free, two stage thermal desorption system for single sorbent tubes.  ULTRA combines with UNITY to automate desorption of up to 100 tubes. ULTRA 50:50 and AutoSecure TD systems offer automation of both thermal desorption and re-collection (Secure TD-Q)

Key standard methods

All Markes TD systems offer full compliance with key standard methods specifying diffusive or pumped sampling onto industry-standard sized sorbent tubes followed by TD-GC(MS) analysis; - ISO 16017, US EPA TO-17, ASTM D6196, NIOSH 2549, etc.  Although solvent extraction (e.g. with carbon disulphide) is still occasionally used for higher concentration air monitoring applications the reliability and automation of thermal desorption, mean that TD is now becoming the universal method of choice.

Every Markes TD system offers SecureTD-Q – quantitative re-collection for repeat analysis and method/data validation. This unique facility overcomes the one-shot limitation of traditional TD methods.  Systems also offer the option of back-pressure regulated electronic pneumatic control of carrier gas through the entire TD-GC(MS) analytical system.  This stabilises retention times independent of operational parameters – split flows, temperatures, sorbents, etc.

Relevant technical support publications from Markes International can be automatically downloaded from this web site (registration required). Examples include:

• Brochures - UNITY, ULTRA, Air Server - Thermal Desorption Systems 
• Brochure - TubeTAG sorbent tube informatics
• TDTS 5 - Advice on sorbent selection and conditioning sample tubes
• TDTS 7 - Calibration: preparing and introducing standards using sorbent tubes
• TDTS 25 - Calculating atmospheric concentrations from analyte masses retained on sorbent tubes
• TDTS 27 - Sampling methods for monitoring VOCs in air by TD-GC(MS)
• TDTS 28 - Optimising analytical performance and extending the application range of thermal desorption for indoor/cabin/vehicle air monitoring
• TDTS 33 - Analysis of the interior atmosphere of a saloon car using thermal desorption and GC/MS
• TDTS 37 - Industrial air monitoring using pumped sampling onto sorbent tubes and the UNITY thermal desorber
• TDTS 38 - Low occupational exposure limit levels favouring analysis by thermal desorption-GC(MS)
• TDTS 46 - Comparing thermal desorption with carbon disulphide (CS₂) extraction of charcoal for air monitoring methods
• TDTS 47 - The analysis of landfill gas compounds using thermal desorption GC/MS and a retention time locked database
• TDTS 49 - Fenceline and ambient monitoring of benzene and other hydrocarbons using diffusive sampling and thermal desorption analysis