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Thermal Desorption Tubes vs. Canister Sampling

Which VOC Sampling Technique is Right for You?

Thermal desorption tubes provide a complementary option to canisters for sampling VOCs. Both techniques have advantages and disadvantages and their features must be evaluated for suitability relative to the sampling environment and analytical capabilities. Enumerated below are the similarities and differences between these techniques; use this handy comparison to determine which equipment is best for you.

Similarities Between Thermal Desorption Tubes and Canisters

  • Reusable sampling device.
  • Long product lifetime.
  • Long-term sample stability.
  • Blank certification required prior to sampling.
  • Sample concentration required before GC/MS analysis.
  • Dry purge helpful to remove moisture before GC injection.
  • Ppt sensitivity.
  • Method acceptance.
  • Collection of wide range of VOCs with single device.
  • Useful for screening of unknowns.
  • Leak tightness critical to maintaining sample integrity and preventing contamination of a clean device.


Differences Between Thermal Desorption Tubes and Canisters

  Thermal Desorption Tubes Canisters
Methods US EPA TO-17
ASTM D6196
ISO 16017, ISO 16000-6
NIOSH 2549
US EPA TO-14, TO-15
ASTM D5466
NIOSH Protocol Draft
  World-wide acceptance Gold standard for US ambient air market
Applications Ambient air, indoor air, industrial hygiene
Material emissions
Food & flavor
Chemical weapons
Ambient air, indoor air, vapor intrusion, emergency response
  C3 to C30 <C3 to ~C10
Handling Light weight for personal monitoring and general ease of use Larger and heavier; more costly to ship
Sampling Active sampling with sampling pump or diffusive sampling without pump is possible with determined diffusion coefficients for each compound. Passive sampling, no sampling pump required. Long-term sampling possible without battery to recharge.
  Integrated sampling only Grab & integrated sampling
  Concentrated sample Whole air
  Proper sorbent selection recommended in methodology. N/A
  Must sample below sorbent breakthrough volumes to avoid sample loss and irreversible adsorption on sorbent N/A
  Large sample volumes >100L Sample volume is function of canister size, 15L max
Analysis Tube dimensions are instrument specific Compatible with all manufacturer sample concentrators
  1 injection, more injections possible for some instrumentation Multiple sample injections
  Concentration range ppt to ppm ppt to ppm
  Some sorbents prone to artifact formation. Low blanks when properly cleaned.
Storage Sample storage at 4°C recommended for multi-bed tubes to prevent potential migration of compounds to more retentive sorbent which maybe difficult to recover. Room temperature
Cleaning Analytical process automatically cleans tube for reuse. Cleans as it analyzes. Conditioning/cleaning and analysis incorporated in one thermal desorption unit. Canister cleaning requires separate equipment as additional step prior to background certification and sampling.
Cost $50-130 each $200-700 each