1、Designation: D6348 121Standard Test Method forDetermination of Gaseous Compounds by Extractive DirectInterface Fourier Transform Infrared (FTIR) Spectroscopy1This standard is issued under the fixed designation D6348; the number immediately following the designation indicates the year oforiginal adop
2、tion 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.1NOTEEditorial corrections were made to A2.3.2.3 in August 2014.INTRODUCTIONThis ext
3、ractive FTIR based field test method is used to quantify gas phase concentrations ofmultiple target analytes from stationary source effluent. Because an FTIR analyzer is potentiallycapable of analyzing hundreds of compounds, this test method is not analyte or source specific. Theanalytes, detection
4、levels, and data quality objectives are expected to change for any particular testingsituation. It is the responsibility of the tester to define the target analytes, the associated detectionlimits for those analytes in the particular source effluent, and the required data quality objectives foreach
5、specific test program. Provisions are included in this test method that require the tester todetermine critical sampling system and instrument operational parameters, and for the conduct ofQA/QC procedures. Testers following this test method will generate data that will allow anindependent observer
6、to verify the valid collection, identification, and quantification of the subjecttarget analytes.1. Scope1.1 This field test method employs an extractive samplingsystem to direct stationary source effluent to an FTIR spec-trometer for the identification and quantification of gaseouscompounds. Concen
7、tration results are provided. This testmethod is potentially applicable for the determination ofcompounds that (1) have sufficient vapor pressure to betransported to the FTIR spectrometer and (2) absorb a sufficientamount of infrared radiation to be detected.1.2 This field test method provides near
8、real time analysis ofextracted gas samples from stationary sources. Gas streamswith high moisture content may require conditioning to mini-mize the excessive spectral absorption features imposed bywater vapor.1.3 This field test method requires the preparation of asource specific field test plan. Th
9、e test plan must include thefollowing: (1) the identification of the specific target analytes(2) the known analytical interferents specific to the test facilitysource effluent (3) the test data quality necessary to meet thespecific test requirements and (4) the results obtained from thelaboratory te
10、sting (see Annex A1 for test plan requirements).1.4 The FTIR instrument range should be sufficient tomeasure from high ppm(v) to ppb(v) and may be extended tohigher or lower concentrations using any or all of the followingprocedures:1.4.1 The gas absorption cell path length may be eitherincreased or
11、 decreased,1.4.2 The sample conditioning system may be modified toreduce the water vapor, CO2, and other interfering compoundsto levels that allow for quantification of the targetcompound(s), and1.4.3 The analytical algorithm may be modified such thatinterfering absorbance bands are minimized or str
12、onger/weakerabsorbance bands are employed for the target analytes.1.5 The practical minimum detectable concentration isinstrument, compound, and interference specific (see AnnexA2 for procedures to estimate the achievable minimum detect-able concentrations (MDCs). The actual sensitivity of theFTIR m
13、easurement system for the individual target analytesdepends upon the following:1.5.1 The specific infrared absorptivity (signal) and wave-length analysis region for each target analyte,1.5.2 The amount of instrument noise (see Annex A6), and1.5.3 The concentration of interfering compounds in thesamp
14、le gas (in particular, percent moisture and CO2), and the1This test method is under the jurisdiction of Committee D22 on Air Quality andis the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres andSource Emissions.Current edition approved Feb. 1, 2012. Published February 2012. Origi
15、nallyapproved in 1998. Last previous edition approved in 2010 as D6348 03 (2010).DOI: 10.1520/D6348-12E01.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1amount of spectral overlap imparted by these compounds in thewavelength region(s
16、) used for the quantification of the targetanalytes.1.5.4 Any sampling system interferences such as adsorptionor outgassing.1.6 Practices E168 and E1252 are suggested for additionalreading.1.7 This standard does not purport to address all of thesafety concerns associated with its use. It is the resp
17、onsibilityof the user of this standard to establish appropriate safety andhealth practices and to determine the applicability of regula-tory limitations prior to use. Additional safety precautions aredescribed in Section 9.2. Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Samp
18、ling and Analysis ofAtmospheresD3195 Practice for Rotameter CalibrationE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE1252 Practice for General Techniques for Obtaining Infra-red Spectra for Qualitative Analysis2.2 EPA Methods (40 CFR Part 60 Appendix A)3Method 1 Sample and
19、 Velocity Traverses for StationarySourcesMethod 2 Series Determination of Stack Gas Velocity andVolumetric Flow Rate (Type S Pitot Tube)Method 3 Series Gas Analysis for Carbon Dioxide, Oxygen,Excess Air, and Dry Molecular WeightMethod 4 Series Determination of Moisture Content in StackGases3. Termin
20、ology3.1 See Terminology D1356 for definition of terms relatedto sampling and analysis of atmospheres.3.2 This section contains the terms and definitions used inthis test method and those that are relevant to extractive FTIRbased sampling and analysis of stationary source effluent.When possible, def
21、initions of terms have been drawn fromauthoritative texts or manuscripts in the fields of air pollutionmonitoring, spectroscopy, optics, and analytical chemistry.3.2.1 absorbance, nthe negative logarithm of thetransmission, A = -log (I/I0), where I is the transmitted intensityof the light and I0is t
22、he incident intensity.3.2.2 absorptivity, adjthe amount of infrared radiation thatis absorbed by each molecule.3.2.3 analyte spiking, nthe process of quantitatively co-adding calibration standards with source effluent to determinethe effectiveness of the FTIR measurement system to quantifythe target
23、 analytes.3.2.4 analytical algorithm, nthe method used to quantifythe concentration of the target analytes and interferences ineach FTIR Spectrum. The analytical algorithm should accountfor the analytical interferences by conducting the analysis in aportion of the infrared spectrum that is the most
24、unique for thatparticular compound.3.2.5 analytical interference, nthe physical effects of su-perimposing two or more light waves. Analytical interferencesoccur when two or more compounds have overlapping absor-bance bands in their infrared spectra.3.2.6 apodization, va mathematical transformation c
25、arriedout on data received from an interferometer to reduce the sidelobes of the measured peaks. This procedure alters the instru-ments response function. There are various types of transfor-mation; the most common forms are boxcar, triangular, Happ-Genzel, and Beer-Norton functions.3.2.7 background
26、 spectrum, nthe spectrum taken in theabsence of absorbing species or sample gas, typically con-ducted using dry nitrogen or zero air in the gas cell.3.2.8 bandwidth, adjthe width of a spectral feature asrecorded by a spectroscopic instrument. This width is listed asthe full width at the half maximum
27、 of the feature or as the halfwidth at the half maximum of the spectral feature. This is alsoreferred to as the line width (1).43.2.9 beam splitter, na device located in the interferometerthat splits the incoming infrared radiation into two separatebeams that travel two separate paths before recombi
28、nation.3.2.10 Beers law, nthe principal by which FTIR spectraare quantified. Beers law states that the intensity of a mono-chromatic plane wave incident on an absorbing medium ofconstant thickness diminishes exponentially with the numberof absorbers in the beam. Strictly speaking, Beers law holdsonl
29、y if the following conditions are met: (1) perfectly mono-chromatic radiation (2) no scattering (3 ) a beam that is strictlycollimated (4) negligible pressure-broadening effects (2, 3).For an excellent discussion of the derivation of Beers law, see(4).3.2.11 calibration transfer standard, na certifi
30、ed calibra-tion standard that is used to verify the instrument stability on adaily basis when conducting sampling.3.2.12 classical least squares, na common method ofanalyzing multicomponent infrared spectra by scaled absor-bance subtraction.3.2.13 condenser system,(dryer), na moisture removalsystem
31、that condenses water vapor from the source effluent toprovide a dry sample to the FTIR gas cell. Part of the sampleconditioning system.3.2.14 cooler, na device into which a quantum detector isplaced for maintaining it at a low temperature in an IR system.At a low temperature, the detector provides t
32、he high sensitivitythat is required for the IR system. The two primary types ofcoolers are a liquid nitrogen Dewar and a closed-cycle Stirlingcycle refrigerator.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book o
33、f ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Superintendent of Documents, U. G. Government PrintingOffice, Washington, DC 20402.4The boldface numbers in parentheses refer to the list of references at the end ofthe standard.D6348
34、12123.2.15 electromagnetic spectrum, nthe total set of allpossible frequencies of electromagnetic radiation. Differentsources may emit over different frequency regions. All elec-tromagnetic waves travel at the same speed in free space (5).3.2.16 extractive FTIR, na means of employing FTIR toquantify
35、 concentrations of gaseous components in stationarysource effluent. It consists of directing gas samples to the FTIRcell without collection on sample media.3.2.17 fingerprint region, nthe region of the absorptionspectrum of a molecule that essentially allows its unequivocalidentification. For exampl
36、e, the organic fingerprint regioncovers the wave number range from 650 to 1300 cm1(6).3.2.18 Fourier transform, va mathematical transform thatallows an aperiodic function to be expressed as an integral sumover a continuous range of frequencies (7). The interferogramrepresents the detector response (
37、intensity) versus time, theFourier transform function produces intensity as a function offrequency.3.2.19 frequency position, nthe accepted exact spectralline position for a specific analyte.Awave number or fractionalwavenumber is used to determine whether spectral shifts haveoccurred with time.3.2.
38、20 FTIR, nan abbreviation for Fourier transform in-frared.Aspectroscopic instrument using the infrared portion ofthe electromagnetic spectrum. The working component of thissystem is an interferometer. To obtain the absorption spectrumas a function of frequency, a Fourier transform of the output ofth
39、e interferometer must be performed. For an in-depth descrip-tion of the FTIR, see (8).3.2.21 fundamental CTS, na NIST traceable referencespectrum with known temperature and pressure, that has beenrecorded with an absorption cell that has been measured usingeither a laser or other suitably accurate p
40、hysical measurementdevice.3.2.22 infrared spectrum, nthat portion of the electromag-netic spectrum that spans the region from about 10 cm1toabout 12 500 cm1. It is divided (6) into (1) the near-infraredregion (from 12 500 to 4000 cm1), (2) the mid-infrared region(from 4000 to 650 cm1), and (3 ) the
41、far-infrared region (from650 to 10 cm1).3.2.23 instrument function, nthe function superimposedon the actual absorption line shape by the instrument. This issometimes referred to as the slit function; a term taken frominstruments that use slits to obtain resolution.3.2.24 instrument specific referenc
42、e spectra, nreferencespectra collected on the instrument that collects the actualsample spectra. The instrument specific reference spectra areused in the analytical algorithm.3.2.25 intensity, nthe radiant power per unit solid angle.When the term spectral intensity is used, the units are watts perst
43、eradian per nanometre. In most spectroscopic literature, theterm intensity is used to describe the power in a collimatedbeam of light in terms of power per unit area per unitwavelength. However, in the general literature, this definitionis more often used for the term irradiance,ornormal irradi-ance
44、 (9, 10).3.2.26 interferogram, nthe effects of interference that aredetected and recorded by an interferometer, the output of theFTIR and the primary data are collected and stored (8, 10).3.2.27 interferometer, nany of several kinds of instru-ments used to produce interference effects. The Michelson
45、interferometer used in FTIR instruments is the most famous ofa class of interferometers that produce interference by thedivision of amplitude (11).3.2.28 irradiance, nradiant power per unit projected areaof a specified surface. This has units of watts per squarecentimetre. The term spectral irradian
46、ce is used to describe theirradiance as a function of wavelength. It has units of watts persquare centimetre per nanometre (9).3.2.29 laser, nan acronym for the term light amplificationby stimulated emission of radiation. A source of light that ishighly coherent, both spatially and temporally (1).3.
47、2.30 light, nstrictly, light is defined as that portion of theelectromagnetic spectrum that causes the sensation of vision. Itextends from about 25 000 cm1to about 14 300 cm1(5).3.2.31 minimum detectable concentration, nthe minimumconcentration of a compound that can be detected by aninstrument with
48、 a given statistical probability. Usually thedetection limit is given as three times the standard deviation ofthe noise in the system. In this case, the minimum concentra-tion can be detected with a probability of 99.7 % (9, 12). SeeAnnexA2 of this standard for a series of procedures to measureMDC.3
49、.2.32 native effluent concentration, nthe underlying ef-fluent concentration of the target analytes.3.2.33 noise equivalent absorbance (NEA), nthe peak-to-peak noise in the spectrum resulting from the acquisition oftwo successive background spectra.3.2.34 path length, nthe distance that the sample gasinteracts with the infrared radiation.3.2.35 peak-to-peak noise, nthe absolute difference fromthe highest positive peak to the lowest negative peak in adefined spectral region.3.2.36 primary particulate matter filter, nfilter of 0.3m
