ASTM D5953M-96
(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)
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 13.4 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 the 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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Designation: D 5953M – 96 An American National Standard
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)
This standard is issued under the fixed designation D 5953M; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers a procedure for sampling and 2.1 ASTM Standards:
determining concentrations of non-methane organic com- D 1193 Specification for Reagent Water
pounds (NMOC) in ambient, indoor, or workplace atmo- D 1356 Terminology Relating to Sampling and Analysis of
spheres. Atmospheres
1.2 The test method describes the collection of cumulative D 1357 Practice for Planning the Sampling of the Ambient
samples in passivated stainless steel canisters and subsequent Atmosphere
laboratory analysis. D 5466 Test Method for the Determination of Volatile
1.2.1 This test method describes a procedure for sampling in Organic Chemicals in Atmospheres (Canister Sampling
canisters at final pressures above atmospheric pressure (re- Methodology)
ferred to as pressurized sampling).
3. Terminology
1.3 This test method employs a cryogenic trapping proce-
3.1 Definitions— For definitions of terms used in this test
dure for concentration of the NMOC prior to analysis.
1.4 This test method describes the determination of the method, refer to Terminology D 1356.
3.2 Definitions of Terms Specific to This Standard:
NMOC by the simple flame ionization detector (FID), without
the gas chromatographic columns and complex procedures 3.2.1 cryogen—a refrigerant used to obtain very low tem-
peratures in the cryogenic traps of the analytical system.
necessary for species separation.
1.5 The range of this test method is from 20 to 10 000 ppbC 3.2.1.1 Discussion—Liquid argon (bp − 185.7°C at stan-
dard pressure) is recommended for this test method. Cryogens
(1, 2). See 13.4 for procedures for lowering the range.
1.6 The test method may yield less accurate results for some with lower boiling points, such as liquid nitrogen, should not
be used because of possible trapping of oxygen from the
halogenated or oxygenated hydrocarbons emitted from nearby
sources of industrial air pollutants. This is especially true if sample air, which might lead to the possibility of an explosion
or fire. In addition, methane would be trapped.
there are high concentrations of chlorocarbons or chlorofluo-
rocarbons present. 3.2.2 dynamic calibration—calibration of an analytical sys-
tem with pollutant concentrations that are generated in a
1.7 The values stated in SI units are regarded as the
dynamic, flowing system, such as by quantitative, flow-rate
standard.
1.8 This standard does not purport to address all of the dilution of a high-concentration gas standard with zero gas.
3.2.3 NMOC—non-methane organic compounds.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.2.3.1 Discussion—Total non-methane organic compounds
are those compounds measured by a flame ionization detector,
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. excluding methane and compounds with vapor pressure above
−2
10 kPa, recovered from the canister.
3.2.4 ppm C and ppb C—concentration units of parts per
This test method is under the jurisdiction of ASTM Committee D-22 on
million and parts per billion of organic carbon as detected by
Sampling and Analysis of Atmospheres and is the direct responsibility of Subcom-
mittee D22.03 on Ambient Atmospheres and Source Emissions.
the FID.
Current edition approved May 10, 1996. Published July 1996.
3.2.4.1 Discussion—During calibration with propane, for
This test method is based on EPA Method TO-12: “Determination of Non-
example, they are equivalent to parts per million by volume
Methane Organic Compounds (NMOC) in Ambient Air Using Cryogenic Pre-
(ppm (v)) or parts per billion by volume (ppb (v)), respectively,
Concentration and Direct Flame Ionization Detection (PDFID)”, Compendium of
Methods for the Determination of Toxic Organic Compounds in Ambient Air ,EPA
multiplied by the number of carbon atoms in propane.
600 4-89-017, U.S. Environmental Protection Agency, Research Triangle Park, NC,
March 1990.
3 4
The boldface numbers in parentheses refer to the list of references at the end of Annual Book of ASTM Standards, Vol 11.01.
this standard. Annual Book of ASTM Standards, Vol 11.03.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 5953M
4. Summary of Test Method (2-6) 5.3 Conventional test methods that depend on gas chroma-
tography and qualitative and quantitative species evaluation are
4.1 An air sample is extracted directly from the ambient air,
excessively difficult and expensive to operate and maintain
collected in a precleaned sample canister and transported to a
when speciated measurements are not needed. The test method
laboratory.
described here involves a simple, cryogenic preconcentration
4.2 A fixed-volume portion of the sample air is drawn from
procedure with subsequent direct detection with the FID. The
the canister at a low flow rate through a glass-bead filled trap
test method is sensitive and provides accurate measurements of
that is cooled to approximately −186°C with liquid argon. The
ambient total NMOC concentrations where speciated data are
cryogenic trap simultaneously collects and concentrates the
not required.
NMOC using condensation, while allowing the nitrogen,
5.4 An application of the test method is the monitoring of
oxygen, methane, and other compounds with boiling points
the cleanliness of canisters.
below −186°C to pass through the trap without retention. The
5.5 Another use of the test method is the screening of
system is dynamically calibrated so that the volume of sample
canister samples prior to analysis.
passing through the trap does not have to be quantitatively
5.6 Collection of ambient air samples in pressurized canis-
measured, but must be precisely repeatable between the cali-
ters provides the following advantages:
bration and the analytical phases.
5.6.1 Convenient integration of ambient samples over a
4.3 After the fixed-volume air sample has been drawn
specific time period,
through the trap, a helium carrier gas flow is diverted to pass
5.6.2 Capability of remote sampling with subsequent central
through the trap, in the opposite direction to the sample flow,
laboratory analysis,
and into an FID. When the residual air and methane have been
5.6.3 Ability to ship and store samples, if necessary,
flushed from the trap and the FID baseline restabilizes, the
5.6.4 Unattended sample collection,
cryogen is removed and the temperature of the trap is raised to
5.6.5 Analysis of samples from multiple sites with one
80 to 90°C.
analytical system,
4.4 The organic compounds previously collected in the trap
5.6.6 Collection of replicate samples for assessment of
revolatilize due to the increase in temperature and are carried
measurement precision, and
into the FID, resulting in a response peak or peaks from the
5.6.7 Specific hydrocarbon analysis can be performed with
FID. The area of the peak or peaks is integrated, and the
the same sample system.
integrated value is translated to concentration units using a
previously obtained calibration curve relating integrated peak
6. Interferences
areas with known concentrations of propane.
6.1 In laboratory evaluations, moisture in the sample has
4.5 The cryogenic trap simultaneously concentrates the
been found to cause a positive shift in the FID baseline. The
NMOC while separating and removing the methane from air
effect of this shift is minimized by carefully selecting the
samples. The technique is thus direct reading using FID for
integration termination point and adjusting the baseline used
NMOC and, because of the concentration step, it is more
for calculating the area of the NMOC peaks.
sensitive than conventional continuous NMOC analyzers.
6.2 With helium as a carrier gas, FID response is quite
4.6 The sample is injected into the hydrogen-rich flame of
uniform for most hydrocarbon compounds, but the response
the FID, where the organic vapors burn, producing ionized
can vary considerably for other types of organic compounds.
molecular fragments. The resulting ion fragments are then
collected and detected. Because this test method employs a
7. Apparatus
helium carrier gas, the detector response is nearly identical for
7.1 Sample Collection System, (Fig. 1).
many hydrocarbon compounds of interest. Thus, the historical
7.1.1 Sample Canister(s), stainless steel, Summa -polished
short-coming of varying FID response to aromatic, olefinic,
vessel(s) of 4 to 6 L capacity, used for automatic collection of
and paraffinic hydrocarbons is minimized. The FID is much
integrated field air samples.
less sensitive to most organic compounds containing functional
7.1.1.1 Mark each canister with a unique identification
groups such as carbonyls, alcohols, halocarbons, etc.
number stamped on its frame.
7.1.2 Sample Pump, stainless steel, metal bellows type.
5. Significance and Use
7.1.2.1 Ensure that the pump is free of leaks, and uncon-
5.1 Many industrial processes require determination of
taminated by oil or organic compounds.
NMOC in the atmosphere.
7.1.2.2 Shock mount the pump to minimize vibration.
5.2 Accurate measurements of ambient concentrations of
7.1.3 Pressure Gage, 0 to 210 kPa (0 to 30 psig).
NMOC are important for the control of photochemical smog
7.1.4 Solenoid Valve, controls the sample flow to the canis-
because these organic compounds are primary precursors of
ter with negligible temperature rise.
atmospheric ozone and other oxidants (7, 8).
7.1.5 Flow Control Device, mass flowmeter, critical orifice,
5.2.1 The NMOC concentrations typically found at urban
or short capillary to maintain the sample flow over the
sites may range up to 1 to 3 ppm C or higher. In order to
sampling period.
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
The Summa process is a trademark of Molectrics, Inc., 4000 E. 89th St.,
sources are likely to be less than a few tenths of 1 ppm C. Cleveland, OH 44105.
D 5953M
taining a stable flame throughout all phases of the analytical
cycle.
7.3.2 Data Reduction Device, such as a computer, equipped
with data acquisition hardware and software and a laser printer,
or an electronic integrator, with chart recorder, capable of
integrating the area of one or more FID response peaks and
calculating peak area corrected for baseline drift.
7.3.2.1 If a separate integrator and chart recorder are used,
exercise care to ensure that these components do not interfere
with each other electrically or electronically.
7.3.2.2 Range selector controls on both the integrator and
the FID analyzer may not provide accurate range ratios, so
prepare individual calibration curves for each range.
7.3.2.3 The integrator must be capable of marking the
beginning and ending of peaks, constructing the appropriate
baseline between the start and end of the integration period,
and calculating the peak area.
FIG. 1 Sample System for Automatic Collection of Integrated Air
7.3.3 Cryogenic Trap, constructed from a single piece of
Samples
chromatographic-grade stainless steel tubing (3 mm outside
diameter, 2 mm inside diameter), as shown in Fig. 4.
7.3.3.1 Pack the central portion of the trap (70 to 100 mm)
7.1.6 Particulate Matter Filter, inert in-line filter, 2μ m or
with silanized 180 to 250 μm (60/80 mesh) glass beads, with
less, or other suitable filter, used to filter the air sample.
small silanized glass wool plugs, to retain the beads.
7.1.7 Auxiliary Vacuum Pump or Blower, draws sample air
7.3.3.2 The arms of the trap must be of such length to permit
through the sample inlet line to reduce inlet residence time to
the beaded portion of the trap to be submerged below the level
no greater than 10 s.
of cryogen in the Dewar flask.
7.1.7.1 Shock mount the pump to minimize vibration.
7.3.3.3 Connect the trap directly to the six-port valve (7.3.4)
7.1.8 Timer, programmable, and electrically connected to
to minimize the line length between the trap (7.3.3) and the
the solenoid valve (7.1.4) and pumps (7.1.2 and 7.1.7), capable
FID (7.3.1).
of controlling the pumps and the solenoid valve.
7.3.3.4 Mount the trap to allow clearance so the Dewar flask
7.1.9 Sample Inlet Line, transports the sample air into the
may be applied and withdrawn to facilitate cooling and heating
sample system, consisting of stainless steel tubing components.
the trap (see 7.3.12).
7.2 Sample Canister Cleaning System, (Fig. 2).
7.3.4 Six-Port Valve— Locate the six-port valve and as
7.2.1 Vacuum Pump, capable of evacuating sample canis-
much of the interconnecting tubing as practical inside an oven
ter(s) to an absolute pressure of # 2 Pa (15 μm Hg).
or otherwise heat it to 80 to 90°C to minimize wall losses or
7.2.2 Manifold, stainless steel manifold with connections
adsorption/desorption in the connecting tubing. All lines must
for simultaneously cleaning several canisters.
be as short as practical.
7.2.3 Shut-off Valve(s), nine required.
7.3.5 Multistage Pressure Regulators (3 required), standard
7.2.4 Pressure Gage, 0 to 350 kPa (0 to 50 psig)–monitors
two-stage, stainless steel diaphragm regulators with pressure
zero-air pressure.
gages, for helium, air, and hydrogen cylinders.
7.2.5 Cryogenic Trap (2 required), U-shaped open tubular
7.3.6 Auxilliary Flow or Pressure Regulators (2 required),
trap cooled with liquid argon used to prevent contamination
to maintain constant flow rates, within 1 mL/min for the helium
from back diffusion of oil from vacuum pump, and providing
carrier and the hydrogen.
clean, zero-air to the sample canister(s).
7.3.7 Fine Needle Valve (2 required)—One adjusts the
7.2.6 Vacuum Gage, capable of measuring vacuum in the
sample flow rate through the trap, and the other adjusts the
manifold to an absolute pressure of 15 Pa (0.1 mm Hg) or less,
sample flow rate from the canister.
with scale divisions of 0.1 Pa (0.5 μm Hg).
7.3.8 Dewar Flask, holds cryogen used to cool the trap,
7.2.7 Flow Control Valve, regulates flow of zero-air into the
sized to contain the submerged portion of the trap.
canister(s).
7.3.
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