ASTM D5953M-96(2009)
(Test Method)Standard Test Method for Determination of Non-Methane Organic Compounds (NMOC) in Ambient Air Using Cryogenic Preconcentration and Direct Flame Ionization Detection Method (Metric)
Standard Test Method for Determination of Non-Methane Organic Compounds (NMOC) in Ambient Air Using Cryogenic Preconcentration and Direct Flame Ionization Detection Method (Metric)
SIGNIFICANCE AND USE
Many industrial processes require determination of NMOC in the atmosphere.
Accurate measurements of ambient concentrations of NMOC are important for the control of photochemical smog because these organic compounds are primary precursors of atmospheric ozone and other oxidants (7, 8).
The NMOC concentrations typically found at urban sites may range up to 1 to 3 ppm C or higher. In order to determine transport of precursors into an area, measurement of NMOC upwind of the area may be necessary. Rural NMOC concentrations originating from areas free from NMOC sources are likely to be less than a few tenths of 1 ppm C.
Conventional test methods that depend on gas chromatography and qualitative and quantitative species evaluation are excessively difficult and expensive to operate and maintain when speciated measurements are not needed. The test method described here involves a simple, cryogenic preconcentration procedure with subsequent direct detection with the FID. The test method is sensitive and provides accurate measurements of ambient total NMOC concentrations where speciated data are not required.
An application of the test method is the monitoring of the cleanliness of canisters.
Another use of the test method is the screening of canister samples prior to analysis.
Collection of ambient air samples in pressurized canisters provides the following advantages:
Convenient integration of ambient samples over a specific time period,
Capability of remote sampling with subsequent central laboratory analysis,
Ability to ship and store samples, if necessary,
Unattended sample collection,
Analysis of samples from multiple sites with one analytical system,
Collection of replicate samples for assessment of measurement precision, and
Specific hydrocarbon analysis can be performed with the same sample system.
SCOPE
1.1 This test method covers a procedure for sampling and determining concentrations of non-methane organic compounds (NMOC) in ambient, indoor, or workplace atmospheres.
1.2 The test method describes the collection of cumulative samples in passivated stainless steel canisters and subsequent laboratory analysis.
1.2.1 This test method describes a procedure for sampling in canisters at final pressures above atmospheric pressure (referred to as pressurized sampling).
1.3 This test method employs a cryogenic trapping procedure for concentration of the NMOC prior to analysis.
1.4 This test method describes the determination of the NMOC by the simple flame ionization detector (FID), without the gas chromatographic columns and complex procedures necessary for species separation.
1.5 The range of this test method is from 20 to 10 000 ppbC (1, 2). See for procedures for lowering the range.
1.6 The test method may yield less accurate results for some halogenated or oxygenated hydrocarbons emitted from nearby sources of industrial air pollutants. This is especially true if there are high concentrations of chlorocarbons or chlorofluorocarbons present.
1.7 The values stated in SI units are regarded as standard.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D5953M − 96(Reapproved 2009)
Standard Test Method for
Determination of Non-Methane Organic Compounds (NMOC)
in Ambient Air Using Cryogenic Preconcentration and Direct
Flame Ionization Detection Method
This standard is issued under the fixed designation D5953M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers a procedure for sampling and
responsibility of the user of this standard to establish appro-
determining concentrations of non-methane organic com-
priate safety and health practices and determine the applica-
pounds (NMOC) in ambient, indoor, or workplace atmo-
bility of regulatory limitations prior to use.
spheres.
1.2 The test method describes the collection of cumulative 2. Referenced Documents
samples in passivated stainless steel canisters and subsequent
2.1 ASTM Standards:
laboratory analysis.
D1193Specification for Reagent Water
1.2.1 Thistestmethoddescribesaprocedureforsamplingin
D1356Terminology Relating to Sampling and Analysis of
canisters at final pressures above atmospheric pressure (re-
Atmospheres
ferred to as pressurized sampling).
D1357Practice for Planning the Sampling of the Ambient
Atmosphere
1.3 This test method employs a cryogenic trapping proce-
D5466Test Method for Determination of Volatile Organic
dure for concentration of the NMOC prior to analysis.
Chemicals inAtmospheres (Canister Sampling Methodol-
1.4 This test method describes the determination of the
ogy)
NMOC by the simple flame ionization detector (FID), without
the gas chromatographic columns and complex procedures
3. Terminology
necessary for species separation.
3.1 Definitions—For definitions of terms used in this test
1.5 Therangeofthistestmethodisfrom20to10000ppbC
method, refer to Terminology D1356.
(1, 2). See for procedures for lowering the range.
3.2 Definitions of Terms Specific to This Standard:
1.6 Thetestmethodmayyieldlessaccurateresultsforsome
3.2.1 cryogen—a refrigerant used to obtain very low tem-
halogenated or oxygenated hydrocarbons emitted from nearby
peratures in the cryogenic traps of the analytical system.
sources of industrial air pollutants. This is especially true if
3.2.1.1 Discussion—Liquidargon(bp−185.7°Catstandard
there are high concentrations of chlorocarbons or chlorofluo-
pressure) is recommended for this test method. Cryogens with
rocarbons present.
lower boiling points, such as liquid nitrogen, should not be
used because of possible trapping of oxygen from the sample
1.7 The values stated in SI units are regarded as standard.
air, which might lead to the possibility of an explosion or fire.
In addition, methane would be trapped.
3.2.2 dynamic calibration—calibration of an analytical sys-
This is under the jurisdiction ofASTM Committee D22 on Air Quality and is
tem with pollutant concentrations that are generated in a
the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres and
Source Emissions.
dynamic, flowing system, such as by quantitative, flow-rate
Current edition approved Oct. 1, 2009. Published December 2009. Originally
dilution of a high-concentration gas standard with zero gas.
approved in 1996. Last previous edition approved in 2001 as D5953M-96 (2001).
DOI: 10.1520/D5953M-96R09.
3.2.3 NMOC—non-methane organic compounds.
This test method is based on EPA Method TO-12: “Determination of Non-
3.2.3.1 Discussion—Total non-methane organic compounds
Methane Organic Compounds (NMOC) in Ambient Air Using Cryogenic Pre-
Concentration and Direct Flame Ionization Detection (PDFID)”, Compendium of
Methods for the Determination of Toxic Organic Compounds in Ambient Air,EPA
600 4-89-017, U.S. Environmental ProtectionAgency, ResearchTriangle Park, NC, For referenced ASTM standards, visit the ASTM website, www.astm.org, or
March 1990. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5953M − 96 (2009)
are those compounds measured by a flame ionization detector, 5. Significance and Use
excluding methane and compounds with vapor pressure above
5.1 Many industrial processes require determination of
−2
10 kPa, recovered from the canister.
NMOC in the atmosphere.
3.2.4 ppm C and ppb C—concentration units of parts per
5.2 Accurate measurements of ambient concentrations of
million and parts per billion of organic carbon as detected by
NMOC are important for the control of photochemical smog
the FID.
because these organic compounds are primary precursors of
3.2.4.1 Discussion—During calibration with propane, for
atmospheric ozone and other oxidants (7, 8).
example, they are equivalent to parts per million by volume
5.2.1 The NMOC concentrations typically found at urban
(ppm(v))orpartsperbillionbyvolume(ppb(v)),respectively,
sites may range up to 1 to 3 ppm C or higher. In order to
multiplied by the number of carbon atoms in propane.
determinetransportofprecursorsintoanarea,measurementof
NMOC upwind of the area may be necessary. Rural NMOC
4. Summary of Test Method (2-6)
concentrations originating from areas free from NMOC
4.1 An air sample is extracted directly from the ambient air,
sources are likely to be less than a few tenths of 1 ppm C.
collected in a precleaned sample canister and transported to a
5.3 Conventional test methods that depend on gas chroma-
laboratory.
tographyandqualitativeandquantitativespeciesevaluationare
4.2 Afixed-volume portion of the sample air is drawn from
excessively difficult and expensive to operate and maintain
the canister at a low flow rate through a glass-bead filled trap
when speciated measurements are not needed.The test method
that is cooled to approximately −186°C with liquid argon. The
described here involves a simple, cryogenic preconcentration
cryogenic trap simultaneously collects and concentrates the
procedure with subsequent direct detection with the FID. The
NMOC using condensation, while allowing the nitrogen,
testmethodissensitiveandprovidesaccuratemeasurementsof
oxygen, methane, and other compounds with boiling points
ambient total NMOC concentrations where speciated data are
below −186°C to pass through the trap without retention. The
not required.
system is dynamically calibrated so that the volume of sample
5.4 An application of the test method is the monitoring of
passing through the trap does not have to be quantitatively
the cleanliness of canisters.
measured, but must be precisely repeatable between the cali-
bration and the analytical phases.
5.5 Another use of the test method is the screening of
canister samples prior to analysis.
4.3 After the fixed-volume air sample has been drawn
through the trap, a helium carrier gas flow is diverted to pass
5.6 Collection of ambient air samples in pressurized canis-
through the trap, in the opposite direction to the sample flow, ters provides the following advantages:
and into an FID.When the residual air and methane have been
5.6.1 Convenient integration of ambient samples over a
flushed from the trap and the FID baseline restabilizes, the
specific time period,
cryogen is removed and the temperature of the trap is raised to
5.6.2 Capabilityofremotesamplingwithsubsequentcentral
80 to 90°C.
laboratory analysis,
5.6.3 Ability to ship and store samples, if necessary,
4.4 The organic compounds previously collected in the trap
revolatilize due to the increase in temperature and are carried
5.6.4 Unattended sample collection,
into the FID, resulting in a response peak or peaks from the
5.6.5 Analysis of samples from multiple sites with one
FID. The area of the peak or peaks is integrated, and the
analytical system,
integrated value is translated to concentration units using a
5.6.6 Collection of replicate samples for assessment of
previously obtained calibration curve relating integrated peak
measurement precision, and
areas with known concentrations of propane.
5.6.7 Specific hydrocarbon analysis can be performed with
4.5 The cryogenic trap simultaneously concentrates the the same sample system.
NMOC while separating and removing the methane from air
samples. The technique is thus direct reading using FID for 6. Interferences
NMOC and, because of the concentration step, it is more
6.1 In laboratory evaluations, moisture in the sample has
sensitive than conventional continuous NMOC analyzers.
been found to cause a positive shift in the FID baseline. The
4.6 The sample is injected into the hydrogen-rich flame of effect of this shift is minimized by carefully selecting the
the FID, where the organic vapors burn, producing ionized integration termination point and adjusting the baseline used
for calculating the area of the NMOC peaks.
molecular fragments. The resulting ion fragments are then
collected and detected. Because this test method employs a
6.2 With helium as a carrier gas, FID response is quite
helium carrier gas, the detector response is nearly identical for
uniform for most hydrocarbon compounds, but the response
many hydrocarbon compounds of interest. Thus, the historical
can vary considerably for other types of organic compounds.
short-coming of varying FID response to aromatic, olefinic,
and paraffinic hydrocarbons is minimized. The FID is much
7. Apparatus
lesssensitivetomostorganiccompoundscontainingfunctional
groups such as carbonyls, alcohols, halocarbons, etc. 7.1 Sample Collection System, (Fig. 1).
D5953M − 96 (2009)
7.2.5 Cryogenic Trap (2 required), U-shaped open tubular
trap cooled with liquid argon used to prevent contamination
from back diffusion of oil from vacuum pump, and providing
clean, zero-air to the sample canister(s).
7.2.6 Vacuum Gauge, capable of measuring vacuum in the
manifoldtoanabsolutepressureof15Pa(0.1mmHg)orless,
with scale divisions of 0.1 Pa (0.5 µm Hg).
7.2.7 Flow Control Valve, regulates flow of zero-air into the
canister(s).
7.2.8 Humidifier, water bubbler or other system capable of
providing moisture to the zero-air supply.
7.2.9 Isothermal Oven, for heating canisters, not shown in
Fig. 2.
7.3 Analytical System, (Fig. 3).
7.3.1 FID System, includes flow controls for the FID fuel
andcombustionair,temperaturecontrolfortheFID,andsignal
FIG. 1 Sample System for Automatic Collection of Integrated Air
processing electronics. Set the FID combustion air, hydrogen,
Samples
and helium carrier flow rates as defined by the manufacturer’s
instructions to obtain an adequate FID response while main-
taining a stable flame throughout all phases of the analytical
7.1.1 Sample Canister(s), stainless steel, Summa -polished
cycle.
vessel(s) of 4 to 6 L capacity, used for automatic collection of
7.3.2 Data Reduction Device, such as a computer, equipped
integrated field air samples.
withdataacquisitionhardwareandsoftwareandalaserprinter,
7.1.1.1 Mark each canister with a unique identification
or an electronic integrator, with chart recorder, capable of
number stamped on its frame.
integrating the area of one or more FID response peaks and
7.1.2 Sample Pump, stainless steel, metal bellows type.
calculating peak area corrected for baseline drift.
7.1.2.1 Ensure that the pump is free of leaks, and uncon-
7.3.2.1 If a separate integrator and chart recorder are used,
taminated by oil or organic compounds.
exercise care to ensure that these components do not interfere
7.1.2.2 Shock mount the pump to minimize vibration.
with each other electrically or electronically.
7.1.3 Pressure Gauge, 0 to 210 kPa (0 to 30 psig).
7.3.2.2 Range selector controls on both the integrator and
7.1.4 Solenoid Valve, controls the sample flow to the canis-
the FID analyzer may not provide accurate range ratios, so
ter with negligible temperature rise.
prepare individual calibration curves for each range.
7.1.5 Flow Control Device, mass flowmeter, critical orifice,
or short capillary to maintain the sample flow over the 7.3.2.3 The integrator must be capable of marking the
sampling period. beginning and ending of peaks, constructing the appropriate
7.1.6 Particulate Matter Filter, inert in-line filter, 2µ m or baseline between the start and end of the integration period,
less, or other suitable filter, used to filter the air sample. and calculating the peak area.
7.1.7 Auxiliary Vacuum Pump or Blower, draws sample air
7.3.3 Cryogenic Trap, constructed from a single piece of
through the sample inlet line to reduce inlet residence time to
chromatographic-grade stainless steel tubing (3 mm outside
no greater than 10 s.
diameter, 2 mm inside diameter), as shown in Fig. 4.
7.1.7.1 Shock mount the pump to minimize vibration.
7.3.3.1 Pack the central portion of the trap (70 to 100 mm)
7.1.8 Timer, programmable, and electrically connected to
with silanized 180 to 250 µm (60/80 mesh) glass beads, with
thesolenoidvalve(7.1.4)andpumps(7.1.2and7.1.7),capable
small silanized glass wool plugs, to retain the beads.
of controlling the pumps and the solenoid valve.
7.3.3.2 Thearmsofthetrapmustbeofsuchlengthtopermit
7.1.9 Sample Inlet Line, transports the sample air into the
the beaded portion of the trap to be submerged below the level
samplesystem,consistingofstainlesssteeltubingcomponents.
of cryogen in the Dewar flask.
7.2 Sample Canister Cleaning System, (Fig. 2).
7.3.3.3 Connectthetrapdirectlytothesix-portvalve(7.3.4)
7.2.1 Vacuum Pump, capable of evacuating sample canis-
to minimize the line length between the trap (7.3.3) and the
ter(s) to an absolute pressure of ≤ 2 Pa (15 µm Hg).
FID (7.3.1).
7.2.2 Manifold, stainless steel manifold with connections
7.3.3.4 MountthetraptoallowclearancesotheDewarflask
for simultaneously cleaning several canisters.
maybeappliedandwithdrawntofacilitatecoolingandheating
7.2.3 Shut-off Valve(s), nine required.
the trap (see 7.3.12).
7.2.4 Pressure Gauge, 0 to 350 kPa (0 to 50 psig)–monitors
7.3.4 Six-Port Valve— Locate the six-port valve and as
zero-air pressure.
much of the interconnecting tubing as practical inside an oven
or otherwise heat it to 80 to 90°C to minimize wall losses or
adsorption/desorption in the connecting tubing. All lines must
The Summa process is a trademark of Molectrics, Inc., 4000 E. 89th St.,
Cleveland, OH 44105. be as short as practical.
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