ASTM D5953M-2016 8168 Standard Test Method for Determination of Non-methane Organic Compounds (NMOC) in Ambient Air Using Cryogenic Preconcentration and Direct Flame Ionization Det.pdf

1、Designation: D5953M 16Standard Test Method forDetermination of Non-methane Organic Compounds (NMOC)in Ambient Air Using Cryogenic Preconcentration and DirectFlame Ionization Detection1This standard is issued under the fixed designation D5953M; the number immediately following the designation indicat

2、es 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 method2presents a procedure for sam

3、pling anddetermination of non-methane organic compounds (NMOC) inambient, indoor, or workplace atmospheres.1.2 This test method describes the collection of integratedwhole air samples in silanized or other passivated stainlesssteel canisters, and their subsequent laboratory analysis.1.2.1 This test

4、method describes a procedure for sampling incanisters at final pressures above atmospheric pressure (pres-surized 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 of theNMOC by the

5、flame ionization detection (FID), without theuse of gas chromatographic columns and other proceduresnecessary for species separation.1.5 The range of this test method is from 20 to 10 000ppb C (1, 2).31.6 This test method has a larger uncertainty for somehalogenated or oxygenated hydrocarbons than f

6、or simplehydrocarbons or aromatic compounds. This is especially true ifthere are high concentrations of chlorocarbons or chlorofluo-rocarbons present.1.7 The values stated in SI units are to be regarded asstandard. The values given in parentheses are mathematicalconversions to inch-pound units that

7、are provided for informa-tion only and are not considered standard.1.8 This standard does 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 ap

8、plica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards: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

9、 Volatile OrganicCompounds in Atmospheres (Canister Sampling Method-ology)2.2 Other References:EPAMethod TO-12 Determination of Non-Methane OrganicCompounds (NMOC) in Ambient Air Using CryogenicPre-Concentration and Direct Flame Ionization Detection(PDFID)53. Terminology3.1 DefinitionsFor definition

10、s 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 analytical system cryogenic traps.3.2.1.1 DiscussionLiquid argon (bp 185.7C at standardpressure) is recommended and ma

11、y be required for use in someapplications of this test method. Cryogens with lower boiling1This is under the jurisdiction of ASTM Committee D22 on Air Quality and isthe direct responsibility of Subcommittee D22.03 on Ambient Atmospheres andSource Emissions.Current edition approved Oct. 1, 2016. Publ

12、ished October 2016. Originallyapproved in 1996. Last previous edition approved in 2009 as D5953M 96 (2009).DOI: 10.1520/D5953M-16.2This test method is based on EPACompendium MethodTO-12: “Determinationof Non-Methane Organic Compounds (NMOC) in Ambient Air Using CryogenicPre-Concentration and Direct

13、Flame Ionization Detection (PDFID),” Compendiumof Methods for the Determination of Toxic Organic Compounds in Ambient Air,EPA600 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 ofthi

14、s standard.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.5Available from United States Environmental Protec

15、tionAgency (EPA), WilliamJefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,http:/www.epa.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1points, such as liquid nitrogen, may be used if the cryogenictrap tem

16、perature is actively maintained at 185C to avoid thepotential for trapping oxygen or methane from air samples.3.2.2 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 hi

17、gh-concentration gas standard with zero gas.3.2.3 NMOCnon-methane organic compounds.3.2.3.1 DiscussionTotal non-methane organic compoundsare compounds, excluding methane, measured using a flameionization detector (FID), with vapor pressures above 102kParecovered from canisters.3.2.4 ppm C and ppb Cc

18、oncentration units of parts-per-million and parts-per-billion of organic carbon as detected byFID.3.2.4.1 DiscussionFor example, when calibrating withpropane, concentrations of NMOC in samples are equivalent toparts-per-million by volume (ppm (v) or parts-per-billion byvolume (ppb (v) multiplied by

19、the number of carbon atoms inpropane, which is three (3).4. Summary of Test Method (2-6)4.1 An air sample is collected directly from ambient air,using a pre-cleaned sample evacuated passivated canister,which is then transported to a laboratory.4.2 A fixed-volume portion of the sample air is drawn fr

20、omthe canister at a low flow rate through a silanized glass-beadfilled trap that is cooled to approximately 186C with liquidargon. The cryogenic trap simultaneously collects and concen-trates the NMOC using condensation, while allowing thenitrogen, oxygen, methane, and other compounds with boilingpo

21、ints below 186C to pass through the trap without retention.The system is dynamically calibrated so that the volume ofsample passing through the trap does not have to be quantita-tively measured, but must be precisely repeatable between thecalibration and the analytical phases.4.3 After the fixed-vol

22、ume 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 and methane have beenflushed from the trap and the FID baseline restabilizes, thecryogen is removed and th

23、e temperature of the trap is raised to90C at 30C per minute.4.4 The organic compounds previously collected on the trapre-volatilize and are carried into the FID, resulting in aresponse peak or peaks from the FID. The area of the peak orpeaks is integrated, and the integrated value is translated toco

24、ncentration units using a previously obtained calibrationcurve relating integrated peak areas with known concentrationsof propane or other calibrant.4.5 The cryogenic trap simultaneously concentrates theNMOC while separating and removing the methane fromsamples. The technique thus directly measures

25、NMOC withgreater sensitivity than conventional continuous NMOC ana-lyzers due to the pre-concentration procedure.4.6 The sample is injected into the hydrogen-rich flame ofan FID, where the organic vapors burn, producing ionizedmolecular fragments. The resulting ion fragments are thencollected and de

26、tected. Because this test method employs ahelium carrier gas, the detector response is nearly identical formany hydrocarbon compounds commonly of interest.Thus, thehistorical short-coming of varying FID response to aromatic,olefinic, and paraffinic hydrocarbons is minimized. Users arecautioned that

27、the FID is much less sensitive to most organiccompounds containing functional groups such as carbonyls,alcohols, halocarbons, etc. than simple hydrocarbons.5. Significance and Use5.1 Many regulators, industrial processes, and other stake-holders require determination of NMOC in atmospheres.5.2 Accur

28、ate measurements of ambient NMOC concentra-tions are critical in devising air pollution control strategies andin assessing control effectiveness because NMOCs are primaryprecursors of atmospheric ozone and other oxidants (7, 8).5.2.1 The NMOC concentrations typically found at urbansites may range up

29、 to 1 to 3 ppm C or higher. In order todetermine transport of precursors into an area monitoring site,measurement of NMOC upwind of the site may be necessary.Rural NMOC concentrations originating from areas free fromNMOC sources are likely to be less than a few tenths of 1 ppmC.5.3 Conventional test

30、 methods based upon gas chromatog-raphy and qualitative and quantitative species evaluation arerelatively time consuming, sometimes difficult and expensivein staff time and resources, and are not needed when only ameasurement of NMOC is desired. The test method describedrequires only a simple, cryog

31、enic pre-concentration procedurefollowed by direct detection with an FID. This test methodprovides a sensitive and accurate measurement of ambient totalNMOC concentrations where speciated data are not required.Typical uses of this standard test method are as follows.5.4 An application of the test me

32、thod is the monitoring ofthe cleanliness of canisters.5.5 Another use of the test method is the screening ofcanister samples prior to analysis.5.6 Collection of ambient air samples in pressurized canis-ters provides the following advantages:5.6.1 Convenient collection of integrated ambient samplesov

33、er a specific time period,5.6.2 Capability of remote sampling with subsequent centrallaboratory analysis,5.6.3 Ability 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 samp

34、les for assessment ofmeasurement precision, and5.6.7 Specific hydrocarbon analysis can be performed withthe same sample system.D5953M 1626. 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 minim

35、ized by carefully selecting theintegration beginning and termination points and adjusting thebaseline used for calculating the area of the NMOC peaks.6.2 With helium as a carrier gas, FID response is uniformfor most hydrocarbon compounds, but the response can varyconsiderably for other types of orga

36、nic compounds such ashalogenated and oxygenated compounds.7. Apparatus7.1 Sample Collection System, (Fig. 1).7.1.1 Sample Canister(s), stainless steel, stainless steel elec-tropolished passivated Summa6-polished or silanized vessel(s)of 4 to 6 L capacity, used for automatic collection of integrateda

37、ir samples.7.1.1.1 Mark each canister with a unique identificationnumber.7.1.2 Sample Pump, stainless steel, 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

38、 210 kPa (0 to 30 psig).7.1.4 Solenoid Valve, controls the sample flow to the canis-ter with negligible temperature rise.7.1.5 Flow Control Device, mass flow controller, micro-metering valve, or critical orifice, to maintain the sample flowover the sampling period.7.1.6 Particulate Matter Filter, in

39、ert in-line filter, 2 m orless, or other suitable filter, used to filter the air sample.7.1.7 Auxiliary Vacuum Pump 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, programma

40、ble, and electrically connected tothe solenoid valve (7.1.4) and pumps (7.1.2 and 7.1.7), capableof controlling the 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 Syst

41、em (Fig. 2).7.2.1 Vacuum Pump, capable of evacuating sample canis-ter(s) to an absolute pressure of 1.69 kPa (29.5 in. Hg).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

42、(0 to 50 psig)monitors zero-air pressure.7.2.5 Cryogenic Trap (2 required), U-shaped open tubulartrap cooled with liquid argon, 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 va

43、cuum in themanifold to an absolute pressure of 1.69 kPa (29.5 in. Hgvacuum) or less, with scale divisions of 0.07 kPa (0.5 m Hg).7.2.7 Flow 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 suppl

44、y.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 for the FID fueland combustion air, temperature control for the FID, and signalprocessing electronics. Set the FID combustion air, hydrogen,and helium carrier fl

45、ow rates according to the manufacturersinstructions.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 andcalculati

46、ng peak area corrected for baseline drift.7.3.2.1 If a discrete 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 provi

47、de accurate range ratios, 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

48、Trap, constructed from 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,

49、 to retain the beads.7.3.3.2 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.6The Summa process is a trademark of Molectrics, Inc., 4000 E. 89th St.,Cleveland, OH 44105.FIG. 1 Sample System for Automatic Collection of Integrated AirSamplesD5953M 163FIG. 2 Canister Cleaning SystemD5953M 164FIG. 3 NMOC Analytical SystemD5953M 1657.3.3.3 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