tech
guides
Thermal desorption application
guides are available for a broad
range of markets. Request your
FREE copy today using these part
numbers.
Environmental Air Monitoring
and Occupational Health & Safety
EVTG1034
Residual Volatiles & Materials
Emissions Testing
GNTG1035
Defense & Forensic
CFTG1036
Food, Flavor, Fragrance &
Odor Profiling
FFTG1037
Thermal Desorpt ion Uni t Tubes
AIR
MONI TORING
15
Phone: 800-356-1688 or 814-353-1300
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. Table I outlines the similarities and differences between these tech-
niques; 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.
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
OSHA PV2120
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
-130 each
-700 each
Table I
Comparison of thermal desorption tube and canister sampling for VOCs.
Differences Between Thermal Desorption Tubes and Canisters
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Tel No : 03 9762 2034 in AUSTRALIA
