Table I
Comparison of thermal desorption tube and canister sampling for
VOCs.
425
SAMPLE HANDLING |
AIR MONITORING
Thermal Desorpt ion Uni t Tubes
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
lit. cat.# EVTG1034
Residual Volatiles & Materials Emissions
Testing
lit. cat.# GNTG1035
Defense & Forensic
lit. cat.# CFTG1036
Food, Flavor, Fragrance & Odor Profiling
lit. cat.# FFTG1037
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 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.
Thermal Desorption Tubes
Canisters
Methods
US EPA TO-17
ASTM D6196
ISO 16017
ISO 16000-6
NIOSH 2549
US EPA TO-14A, 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, 15 L 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
Differences Between Thermal Desorption Tubes and Canisters
free
literature
A Guide toWhole Air
Canister Sampling:
Equipment Needed
and Practical
Techniques for
Collecting Air Samples
lit. cat.# EVTG1073
Thermal Desorption
Tubes: Versatile Air
Sampling for aWide
Range of Applications
lit. cat.# EVFL1065
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from
Website :
E-mail :
TelNo : 03 9762 2034 . . . in AUSTRALIA
Mar 2011
