Method TO-15
Determination of Volatile Organic Compounds (VOCs) In Air Collected
In Specially-Prepared Canisters And Analyzed By Gas Chromatography/Mass
Spectrometry (GC/MS)
Method Overview
- • Ambient air test method often applied to vapor intrusion,
sub-slab and stack test samples.
- • Samples are collected in passivated, electropolished, fused
silica lined, or glass lined canisters.
- • Samples are analyzed by GC/MS in either scan or selective-ion-monitoring
(SIM) mode.
- • Prior to analysis, ambient air samples are concentrated
using a cryogenic concentrator.
- • Results are available in ppb, mg/m3 and ppt.
Target Compounds
- • TO-15 target compound lists (TCLs) are broadly described
in the method. Standard TCLs may vary slightly between laboratories.
(See Enthalpy’s 64-compound TO-15
target compound list.) These compounds are mostly aromatics
or chlorinated alkanes.
- • By using our NIST reference library of more than 129,000
compounds we provide estimated concentrations for many more tentatively
identified compounds (TICs).
- • TO-15 is not effective for highly polar compounds.
- • TO-15 is not good for compounds with very low vapor pressures.
- • TO-15 does not detect formaldehyde, methane, or methanol.
(Methanol is detectable as a TIC.)
Method Summary
- • Enthalpy uses 1.4L and 6L SUMMA-type stainless steel canisters.
The canisters are evacuated to near zero absolute pressure before
sampling.
- • The canister vacuum is used to collect the sample. A flow
controller (standard orifice without gauge) or canister sampler
(Entech CS1200s regulated orifice with gauge for ambient sampling)
regulates flows such that a canister vacuum remains after the sampling
event. We supply canister samplers for 1-hour, 8-hour and 24-hour
run times.
- • The tester should record starting and ending vacuums for
each canister, and local temperature and pressure. Please request
a gauge if needed when ordering canister testing equipment. Note
that Enthalpy’s canister samplers (Entech CS1200s for ambient samples
only) are configured with integrated vacuum gauges.
- • Samples are pressurized with zero air on arrival at the
lab, with temperature and pressure recorded to enable proper dilution
factor calculation.
- • A sample aliquot is transferred from the canister to the
concentrator on the GC/MS. Aliquot size depends on the expected
concentration of total organics in the canister
- • The concentrator is thermally desorbed to a GC/MS. Peak
areas and ionization patterns are compared to the 64-compound initial
calibration. Non-target peaks are compared to our National Institutes
for Standards and Technology reference library.
- • Sample canisters may also be analyzed using other analytical
techniques once non-target compounds are identified.
Quality Assurance
Enthalpy QA includes:
- • Checking the cleanliness of every canister prior to shipping.
Many labs batch clean their cans and check only one can per batch.
- • Daily GC/MS performance tuning.
- • Continuing calibration every 24 hours.
- • Checking certified standard against a second certified
standard.
- • Available audits
- • NELAP Accredited
Shipping Tips
- • Ship SUMMA canisters back in the containers/boxes originally
used in shipping to you.
- • Do NOT ship back on ice.
- • Please note estimated concentrations on your chain of custody,
and whether the sample is from an ambient or stationary source.
Remember to return any vacuum gauges and controllers, and replace
the brass cap or plug fittings on the canisters or controllers as
originally shipped.
- • Important - include a complete Chain of Custody form for
EACH shipping container. (Enthalpy Chain
of Custody form is downloadable as a PDF in our Library section)
Enthalpy Experience
Enthalpy has analyzed ambient canisters by GC/MS since 1997, subsequently
adapting the ambient method TO-14 to stack testing. That method and
now TO-15 are a useful addition to the source tester's repertoire
because GC/MS can identify unknowns in the flue gas. In addition,
the passivated or glass lined canisters can have a holding time of
up to 30 days.
In recent years, vapor intrusion and soil gas projects have become
a substantial percentage of Enthalpy’s TO-15 services. Our significant
canister inventory (over 400 stainless steel canisters) and wide range
of controller configurations permit us to support a variety of air
programs. Analytical resources include four GC/MS analytical systems,
automated canister cleaning facilities and experienced GC/MS scientists
who understand air testing and analysis.
