1、Designation: D5953M 96 (Reapproved 2009)Standard Test Method forDetermination of Non-Methane Organic Compounds (NMOC)in Ambient Air Using Cryogenic Preconcentration and DirectFlame Ionization Detection Method1This standard is issued under the fixed designation D5953M; the number immediately followin
2、g the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method2cov
3、ers a procedure for sampling anddetermining concentrations of non-methane organic com-pounds (NMOC) in ambient, indoor, or workplace atmo-spheres.1.2 The test method describes the collection of cumulativesamples in passivated stainless steel canisters and subsequentlaboratory analysis.1.2.1 This tes
4、t method describes a procedure for sampling incanisters at final pressures above atmospheric pressure (re-ferred to as pressurized sampling).1.3 This test method employs a cryogenic trapping proce-dure for concentration of the NMOC prior to analysis.1.4 This test method describes the determination o
5、f theNMOC by the simple flame ionization detector (FID), withoutthe gas chromatographic columns and complex proceduresnecessary for species separation.1.5 The range of this test method is from 20 to 10 000 ppbC(1, 2).3See for procedures for lowering the range.1.6 The test method may yield less accur
6、ate results for somehalogenated or oxygenated hydrocarbons emitted from nearbysources of industrial air pollutants. This is especially true ifthere are high concentrations of chlorocarbons or chlorofluo-rocarbons present.1.7 The values stated in SI units are regarded as standard.1.8 This standard do
7、es not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Sta
8、ndards:4D1193 Specification for Reagent WaterD1356 Terminology Relating to Sampling and Analysis ofAtmospheresD1357 Practice for Planning the Sampling of the AmbientAtmosphereD5466 Test Method for Determination of Volatile OrganicChemicals in Atmospheres (Canister Sampling Methodol-ogy)3. Terminolog
9、y3.1 Definitions For definitions of terms used in this testmethod, refer to Terminology D1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 cryogena refrigerant used to obtain very low tem-peratures in the cryogenic traps of the analytical system.3.2.1.1 DiscussionLiquid argon (bp 185.7C
10、at stan-dard pressure) is recommended for this test method. Cryogenswith lower boiling points, such as liquid nitrogen, should notbe used because of possible trapping of oxygen from thesample air, which might lead to the possibility of an explosionor fire. In addition, methane would be trapped.3.2.2
11、 dynamic calibrationcalibration of an analytical sys-tem with pollutant concentrations that are generated in adynamic, flowing system, such as by quantitative, flow-ratedilution of a high-concentration gas standard with zero gas.3.2.3 NMOCnon-methane organic compounds.1This is under the jurisdiction
12、 of ASTM Committee on Air Quality and is thedirect responsibility of Subcommittee D22.03 on Ambient Atmospheres and SourceEmissions.Current edition approved Oct. 1, 2009. Published December 2009. Originallyapproved in 1996. Last previous edition approved in 2001 as D5953M - 96 (2001).DOI: 10.1520/D5
13、953M-96R09.2This test method is based on EPA Method TO-12: “Determination of Non-Methane Organic Compounds (NMOC) in Ambient Air Using Cryogenic Pre-Concentration and Direct Flame Ionization Detection (PDFID)”, Compendium ofMethods for the Determination of Toxic Organic Compounds in Ambient Air ,EPA
14、600 4-89-017, U.S. Environmental Protection Agency, Research Triangle Park, NC,March 1990.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
15、tm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3.1 DiscussionTotal non-methane organic compoundsare tho
16、se compounds measured by a flame ionization detector,excluding methane and compounds with vapor pressure above102kPa, recovered from the canister.3.2.4 ppm C and ppb Cconcentration units of parts permillion and parts per billion of organic carbon as detected bythe FID.3.2.4.1 DiscussionDuring calibr
17、ation with propane, forexample, they are equivalent to parts per million by volume(ppm (v) or parts per billion by volume (ppb (v), respectively,multiplied by the number of carbon atoms in propane.4. Summary of Test Method (2-6)4.1 An air sample is extracted directly from the ambient air,collected i
18、n a precleaned sample canister and transported to alaboratory.4.2 A fixed-volume portion of the sample air is drawn fromthe canister at a low flow rate through a glass-bead filled trapthat is cooled to approximately 186C with liquid argon. Thecryogenic trap simultaneously collects and concentrates t
19、heNMOC using condensation, while allowing the nitrogen,oxygen, methane, and other compounds with boiling pointsbelow 186C to pass through the trap without retention. Thesystem is dynamically calibrated so that the volume of samplepassing through the trap does not have to be quantitativelymeasured, b
20、ut must be precisely repeatable between the cali-bration and the analytical phases.4.3 After the fixed-volume air sample has been drawnthrough the trap, a helium carrier gas flow is diverted to passthrough the trap, in the opposite direction to the sample flow,and into an FID. When the residual air
21、and methane have beenflushed from the trap and the FID baseline restabilizes, thecryogen is removed and the temperature of the trap is raised to80 to 90C.4.4 The organic compounds previously collected in the traprevolatilize due to the increase in temperature and are carriedinto the FID, resulting i
22、n a response peak or peaks from theFID. The area of the peak or peaks is integrated, and theintegrated value is translated to concentration units using apreviously obtained calibration curve relating integrated peakareas with known concentrations of propane.4.5 The cryogenic trap simultaneously conc
23、entrates theNMOC while separating and removing the methane from airsamples. The technique is thus direct reading using FID forNMOC and, because of the concentration step, it is moresensitive than conventional continuous NMOC analyzers.4.6 The sample is injected into the hydrogen-rich flame ofthe FID
24、, where the organic vapors burn, producing ionizedmolecular fragments. The resulting ion fragments are thencollected and detected. Because this test method employs ahelium carrier gas, the detector response is nearly identical formany hydrocarbon compounds of interest. Thus, the historicalshort-comi
25、ng of varying FID response to aromatic, olefinic,and paraffinic hydrocarbons is minimized. The FID is muchless sensitive to most organic compounds containing functionalgroups such as carbonyls, alcohols, halocarbons, etc.5. Significance and Use5.1 Many industrial processes require determination ofNM
26、OC in the atmosphere.5.2 Accurate measurements of ambient concentrations ofNMOC are important for the control of photochemical smogbecause these organic compounds are primary precursors ofatmospheric ozone and other oxidants (7, 8).5.2.1 The NMOC concentrations typically found at urbansites may rang
27、e up to 1 to 3 ppm C or higher. In order todetermine transport of precursors into an area, measurement ofNMOC upwind of the area may be necessary. Rural NMOCconcentrations originating from areas free from NMOCsources are likely to be less than a few tenths of 1 ppm C.5.3 Conventional test methods th
28、at depend on gas chroma-tography and qualitative and quantitative species evaluation areexcessively difficult and expensive to operate and maintainwhen speciated measurements are not needed. The test methoddescribed here involves a simple, cryogenic preconcentrationprocedure with subsequent direct d
29、etection with the FID. Thetest method is sensitive and provides accurate measurements ofambient total NMOC concentrations where speciated data arenot required.5.4 An application of the test method is the monitoring ofthe cleanliness of canisters.5.5 Another use of the test method is the screening of
30、canister samples prior to analysis.5.6 Collection of ambient air samples in pressurized canis-ters provides the following advantages:5.6.1 Convenient integration of ambient samples over aspecific time period,5.6.2 Capability of remote sampling with subsequent centrallaboratory analysis,5.6.3 Ability
31、 to ship and store samples, if necessary,5.6.4 Unattended sample collection,5.6.5 Analysis of samples from multiple sites with oneanalytical system,5.6.6 Collection of replicate samples for assessment ofmeasurement precision, and5.6.7 Specific hydrocarbon analysis can be performed withthe same sampl
32、e system.6. Interferences6.1 In laboratory evaluations, moisture in the sample hasbeen found to cause a positive shift in the FID baseline. Theeffect of this shift is minimized by carefully selecting theintegration termination point and adjusting the baseline usedfor calculating the area of the NMOC
33、 peaks.6.2 With helium as a carrier gas, FID response is quiteuniform for most hydrocarbon compounds, but the responsecan vary considerably for other types of organic compounds.7. Apparatus7.1 Sample Collection System,(Fig. 1).7.1.1 Sample Canister(s), stainless steel, Summa5-polishedvessel(s) of 4
34、to 6 L capacity, used for automatic collection ofintegrated field air samples.5The Summa process is a trademark of Molectrics, Inc., 4000 E. 89th St.,Cleveland, OH 44105.D5953M 96 (2009)27.1.1.1 Mark each canister with a unique identificationnumber stamped on its frame.7.1.2 Sample Pump, stainless s
35、teel, metal bellows type.7.1.2.1 Ensure that the pump is free of leaks, and uncon-taminated by oil or organic compounds.7.1.2.2 Shock mount the pump to minimize vibration.7.1.3 Pressure Gauge, 0 to 210 kPa (0 to 30 psig).7.1.4 Solenoid Valve, controls the sample flow to the canis-ter with negligible
36、 temperature rise.7.1.5 Flow Control Device, mass flowmeter, critical orifice,or short capillary to maintain the sample flow over thesampling period.7.1.6 Particulate Matter Filter, inert in-line filter, 2 m orless, or other suitable filter, used to filter the air sample.7.1.7 Auxiliary Vacuum Pump
37、or Blower, draws sample airthrough the sample inlet line to reduce inlet residence time tono greater than 10 s.7.1.7.1 Shock mount the pump to minimize vibration.7.1.8 Timer, programmable, and electrically connected tothe solenoid valve (7.1.4) and pumps (7.1.2 and 7.1.7), capableof controlling the
38、pumps and the solenoid valve.7.1.9 Sample Inlet Line, transports the sample air into thesample system, consisting of stainless steel tubing components.7.2 Sample Canister Cleaning System,(Fig. 2).7.2.1 Vacuum Pump, capable of evacuating sample canis-ter(s) to an absolute pressure of # 2 Pa (15 m Hg)
39、.7.2.2 Manifold, stainless steel manifold with connectionsfor simultaneously cleaning several canisters.7.2.3 Shut-off Valve(s), nine required.7.2.4 Pressure Gauge, 0 to 350 kPa (0 to 50 psig)monitorszero-air pressure.7.2.5 Cryogenic Trap (2 required), U-shaped open tubulartrap cooled with liquid ar
40、gon used to prevent contaminationfrom back diffusion of oil from vacuum pump, and providingclean, zero-air to the sample canister(s).7.2.6 Vacuum Gauge, capable of measuring vacuum in themanifold to an absolute pressure of 15 Pa (0.1 mm Hg) or less,with scale divisions of 0.1 Pa (0.5 m Hg).7.2.7 Flo
41、w Control Valve, regulates flow of zero-air into thecanister(s).7.2.8 Humidifier, water bubbler or other system capable ofproviding moisture to the zero-air supply.7.2.9 Isothermal Oven, for heating canisters, not shown inFig. 2.7.3 Analytical System,(Fig. 3).7.3.1 FID System, includes flow controls
42、 for the FID fueland combustion air, temperature control for the FID, and signalprocessing electronics. Set the FID combustion air, hydrogen,and helium carrier flow rates as defined by the manufacturersinstructions to obtain an adequate FID response while main-taining a stable flame throughout all p
43、hases of the analyticalcycle.7.3.2 Data Reduction Device, such as a computer, equippedwith data acquisition hardware and software and a laser printer,or an electronic integrator, with chart recorder, capable ofintegrating the area of one or more FID response peaks andcalculating peak area corrected
44、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 interferewith each other electrically or electronically.7.3.2.2 Range selector controls on both the integrator andthe FID analyzer may not provide accurate range ratio
45、s, soprepare individual calibration curves for each range.7.3.2.3 The integrator must be capable of marking thebeginning and ending of peaks, constructing the appropriatebaseline between the start and end of the integration period,and calculating the peak area.7.3.3 Cryogenic Trap, constructed from
46、a single piece ofchromatographic-grade stainless steel tubing (3 mm outsidediameter, 2 mm inside diameter), as shown in Fig. 4.7.3.3.1 Pack the central portion of the trap (70 to 100 mm)with silanized 180 to 250 m (60/80 mesh) glass beads, withsmall silanized glass wool plugs, to retain the beads.7.
47、3.3.2 The arms of the trap must be of such length to permitthe beaded portion of the trap to be submerged below the levelof cryogen in the Dewar flask.7.3.3.3 Connect the trap directly to the six-port valve (7.3.4)to minimize the line length between the trap (7.3.3) and theFID (7.3.1).7.3.3.4 Mount
48、the trap to allow clearance so the Dewar flaskmay be applied and withdrawn to facilitate cooling and heatingthe trap (see 7.3.12).7.3.4 Six-Port Valve Locate the six-port valve and asmuch of the interconnecting tubing as practical inside an ovenor otherwise heat it to 80 to 90C to minimize wall loss
49、es oradsorption/desorption in the connecting tubing. All lines mustbe as short as practical.7.3.5 Multistage Pressure Regulators (3 required), standardtwo-stage, stainless steel diaphragm regulators with pressuregauges, for helium, air, and hydrogen cylinders.7.3.6 Auxilliary Flow or Pressure Regulators (2 required),to maintain constant flow rates, within 1 mL/min for the heliumcarrier and the hydrogen.7.3.7 Fine Needle Valve (2 required)One adjusts thesample flow rate through the trap, and the other adjusts thesample flow rate from the canister.FIG. 1 Samp
