ASTM D6348-03(2010)
(Test Method)Standard Test Method for Determination of Gaseous Compounds by Extractive Direct Interface Fourier Transform Infrared (FTIR) Spectroscopy
Standard Test Method for Determination of Gaseous Compounds by Extractive Direct Interface Fourier Transform Infrared (FTIR) Spectroscopy
SIGNIFICANCE AND USE
The FTIR measurements provide for multicomponent on-site analysis of source effluent.
This test method provides the volume concentration of detected analytes. Converting the volume concentration to a mass emission rate using a particular compound's molecular weight, and the effluent volumetric flow rate, temperature and pressure is useful for determining the impact of that compound to the atmosphere.
Known concentrations of target analytes are spiked into the effluent to evaluate the sampling and analytical system's effectiveness for transport and quantification of the target analytes, and to ensure that the data collected are meaningful.
The FTIR measurement data are used to evaluate process conditions, emissions control devices, and for determining compliance with emission standards or other applicable permits.
Data quality objectives for each specific testing program must be specified and outlined in a test plan (Annex A1). Supporting data are available from ASTM Headquarters Request RR:D22-1027.
SCOPE
1.1 This field test method employs an extractive sampling system to direct stationary source effluent to an FTIR spectrometer for the identification and quantification of gaseous compounds. This test method is potentially applicable for the determination of compounds that (1) have sufficient vapor pressure to be transported to the FTIR spectrometer and (2) absorb a sufficient amount of infrared radiation to be detected.
1.2 This field test method provides near real time analysis of extracted gas samples from stationary sources. Gas streams with high moisture content may require conditioning to minimize the excessive spectral absorption features imposed by water vapor.
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Standards Content (Sample)
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Designation: D6348 – 03 (Reapproved 2010)
Standard Test Method for
Determination of Gaseous Compounds by Extractive Direct
Interface Fourier Transform Infrared (FTIR) Spectroscopy
This standard is issued under the fixed designation D6348; 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 (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
ThisextractiveFTIRbasedfieldtestmethodisusedtoquantifygasphaseconcentrationsofmultiple
target analytes from stationary source effluent. Because an FTIR analyzer is potentially capable of
analyzing hundreds of compounds, this test method is not analyte or source specific. The analytes,
detection levels, and data quality objectives are expected to change for any particular testing situation.
Itistheresponsibilityofthetestertodefinethetargetanalytes,theassociateddetectionlimitsforthose
analytes in the particular source effluent, and the required data quality objectives for each specific test
program. Provisions are included in this test method that require the tester to determine critical
sampling system and instrument operational parameters, and for the conduct of QA/QC procedures.
Testers following this test method will generate data that will allow an independent observer to verify
the valid collection, identification, and quantification of the subject target analytes.
1. Scope 1.4.1 The gas absorption cell path length may be either
increased or decreased,
1.1 This field test method employs an extractive sampling
1.4.2 The sample conditioning system may be modified to
system to direct stationary source effluent to an FTIR spec-
reduce the water vapor, CO , and other interfering compounds
trometer for the identification and quantification of gaseous
to levels that allow for quantification of the target com-
compounds. This test method is potentially applicable for the
pound(s), and
determination of compounds that (1) have sufficient vapor
1.4.3 The analytical algorithm may be modified such that
pressure to be transported to the FTIR spectrometer and (2)
interferingabsorbancebandsareminimizedorstronger/weaker
absorb a sufficient amount of infrared radiation to be detected.
absorbance bands are employed for the target analytes.
1.2 Thisfieldtestmethodprovidesnearrealtimeanalysisof
1.5 The practical minimum detectable concentration is in-
extracted gas samples from stationary sources. Gas streams
strument, compound, and interference specific (see Annex A2
with high moisture content may require conditioning to mini-
for procedures to estimate the achievable minimum detectable
mize the excessive spectral absorption features imposed by
concentrations (MDCs)). The actual sensitivity of the FTIR
water vapor.
measurement system for the individual target analytes depends
1.3 This field test method requires the preparation of a
upon the following:
source specific field test plan. The test plan must include the
1.5.1 The specific infrared absorptivity (signal) and wave-
following: (1) the identification of the specific target analytes
length analysis region for each target analyte,
(2) the known analytical interferents specific to the test facility
1.5.2 The amount of instrument noise (see Annex A6), and
source effluent (3) the test data quality necessary to meet the
1.5.3 The concentration of interfering compounds in the
specific test requirements and (4) the results obtained from the
sample gas (in particular, percent moisture and CO ), and the
laboratory testing (see Annex A1 for test plan requirements). 2
amountofspectraloverlapimpartedbythesecompoundsinthe
1.4 The FTIR instrument range should be sufficient to
wavelength region(s) used for the quantification of the target
measure from high ppm(v) to ppb(v) and may be extended to
analytes.
higherorlowerconcentrationsusinganyorallofthefollowing
1.5.4 Any sampling system interferences such as adsorption
procedures:
or outgassing.
1.6 Practices E168 and E1252 are suggested for additional
ThistestmethodisunderthejurisdictionofCommitteeD22onAirQuality and
reading.
is the direct responsibility of Subcommittee D22.03 on Ambient Atmospheres and
Source Emissions. 1.7 This standard does not purport to address all of the
Current edition approved Oct. 1, 2010. Published November 2010. Originally
safety concerns associated with its use. It is the responsibility
approved in 1998. Last previous edition approved in 2003 as D6348 - 03. DOI:
of the user of this standard to establish appropriate safety and
10.1520/D6348-03R10.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6348 – 03 (2010)
health practices and to determine the applicability of regula- 3.2.6 apodization, v—a mathematical transformation car-
tory limitations prior to use. Additional safety precautions are ried out on data received from an interferometer to reduce the
described in Section 9. side lobes of the measured peaks. This procedure alters the
instrument’s response function. There are various types of
2. Referenced Documents
transformation; the most common forms are boxcar, triangular,
2.1 ASTM Standards: Happ-Genzel, and Beer-Norton functions.
3.2.7 background spectrum, n—the spectrum taken in the
D1356 Terminology Relating to Sampling and Analysis of
Atmospheres absence of absorbing species or sample gas, typically con-
ducted using dry nitrogen or zero air in the gas cell.
D3195 Practice for Rotameter Calibration
E168 Practices for General Techniques of Infrared Quanti- 3.2.8 bandwidth, adj—the width of a spectral feature as
recorded by a spectroscopic instrument. This width is listed as
tative Analysis
E1252 Practice for General Techniques for Obtaining Infra- the full width at the half maximum of the feature or as the half
width at the half maximum of the spectral feature. This is also
red Spectra for Qualitative Analysis
3 4
2.2 EPA Methods (40 CFR Part 60 Appendix A) referred to as the line width (1).
3.2.9 beam splitter, n—a device located in the interferom-
Method 1 - Sample and Velocity Traverses for Stationary
eterthatsplitstheincominginfraredradiationintotwoseparate
Sources
beams that travel two separate paths before recombination.
Method 2 Series - Determination of Stack Gas Velocity and
3.2.10 Beer’s law, n—the principal by which FTIR spectra
Volumetric Flow Rate (Type S Pitot Tube)
Method 3 Series - Gas Analysis for Carbon Dioxide, Oxy- are quantified. Beer’s law states that the intensity of a mono-
chromatic plane wave incident on an absorbing medium of
gen, Excess Air, and Dry Molecular Weight
Method 4 Series - Determination of Moisture Content in constant thickness diminishes exponentially with the number
of absorbers in the beam. Strictly speaking, Beer’s law holds
Stack Gases
only if the following conditions are met: (1) perfectly mono-
3. Terminology
chromatic radiation (2) no scattering (3) a beam that is strictly
collimated (4) negligible pressure-broadening effects (2, 3).
3.1 See Terminology D1356 for definition of terms related
For an excellent discussion of the derivation of Beer’s law, see
to sampling and analysis of atmospheres.
(4).
3.2 Definitions of Terms Specific to This Standard—This
3.2.11 calibration transfer standard, n—a certified calibra-
section contains the terms and definitions used in this test
tion standard that is used to verify the instrument stability on a
method and those that are relevant to extractive FTIR based
daily basis when conducting sampling.
sampling and analysis of stationary source effluent. When
3.2.12 classical least squares, n—a common method of
possible, definitions of terms have been drawn from authori-
analyzing multicomponent infrared spectra by scaled absor-
tative texts or manuscripts in the fields of air pollution
bance subtraction.
monitoring, spectroscopy, optics, and analytical chemistry.
3.2.13 condenser system,(dryer), n—a moisture removal
3.2.1 absorbance, n—the negative logarithm of the trans-
system that condenses water vapor from the source effluent to
mission, A = -log (I/I ), where I is the transmitted intensity of
provide a dry sample to the FTIR gas cell. Part of the sample
the light and I is the incident intensity.
conditioning system.
3.2.2 absorptivity, adj—the amount of infrared radiation
3.2.14 cooler, n—a device into which a quantum detector is
that is absorbed by each molecule.
placed for maintaining it at a low temperature in an IR system.
3.2.3 analyte spiking, n—the process of quantitatively co-
At a low temperature, the detector provides the high sensitivity
adding calibration standards with source effluent to determine
that is required for the IR system. The two primary types of
the effectiveness of the FTIR measurement system to quantify
coolers are a liquid nitrogen Dewar and a closed-cycle Stirling
the target analytes.
cycle refrigerator.
3.2.4 analytical algorithm, n—the method used to quantify
3.2.15 electromagnetic spectrum, n—the total set of all
the concentration of the target analytes and interferences in
possible frequencies of electromagnetic radiation. Different
each FTIR Spectrum. The analytical algorithm should account
sources may emit over different frequency regions. All elec-
for the analytical interferences by conducting the analysis in a
tromagnetic waves travel at the same speed in free space (5).
portion of the infrared spectrum that is the most unique for that
3.2.16 extractive FTIR, n—a means of employing FTIR to
particular compound.
quantify concentrations of gaseous components in stationary
3.2.5 analytical interference, n—the physical effects of
source effluent. It consists of directing gas samples to the FTIR
superimposing two or more light waves. Analytical interfer-
cell without collection on sample media.
ences occur when two or more compounds have overlapping
3.2.17 fingerprint region, n—the region of the absorption
absorbance bands in their infrared spectra.
spectrum of a molecule that essentially allows its unequivocal
identification. For example, the organic fingerprint region
2 –1
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
covers the wave number range from 650 to 1300 cm (6).
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 4
Available from Superintendent of Documents, U. G. Government Printing The boldface numbers in parentheses refer to the list of references at the end of
Office, Washington, DC 20402. the standard.
D6348 – 03 (2010)
3.2.18 Fourier transform, v—a mathematical transform that 3.2.29 laser, n—an acronym for the term light amplification
allows an aperiodic function to be expressed as an integral sum by stimulated emission of radiation. A source of light that is
over a continuous range of frequencies (7). The interferogram highly coherent, both spatially and temporally (1).
represents the detector response (intensity) versus time, the
3.2.30 light,n—strictly,lightisdefinedasthatportionofthe
Fourier transform function produces intensity as a function of
electromagnetic spectrum that causes the sensation of vision. It
–1 –1
frequency.
extends from about 25 000 cm to about 14 300 cm (5).
3.2.19 frequency position, n—the accepted exact spectral 3.2.31 minimum detectable concentration, n—the minimum
linepositionforaspecificanalyte.Awavenumberorfractional
concentration of a compound that can be detected by an
wavenumber is used to determine whether spectral shifts have instrument with a given statistical probability. Usually the
occurred with time.
detection limit is given as three times the standard deviation of
the noise in the system. In this case, the minimum concentra-
3.2.20 FTIR, n—an abbreviation for Fourier transform
tion can be detected with a probability of 99.7 % (9, 12). See
infrared.Aspectroscopic instrument using the infrared portion
AnnexA2ofthisstandardforaseriesofprocedurestomeasure
of the electromagnetic spectrum. The working component of
MDC.
this system is an interferometer. To obtain the absorption
spectrum as a function of frequency, a Fourier transform of the 3.2.32 native effluent concentration, n—the underlying ef-
fluent concentration of the target analytes.
output of the interferometer must be performed. For an
in-depth description of the FTIR, see (8).
3.2.33 noise equivalent absorbance (NEA), n—the peak-to-
peak noise in the spectrum resulting from the acquisition of
3.2.21 fundamental CTS, n—a NIST traceable reference
two successive background spectra.
spectrum with known temperature and pressure, that has been
recorded with an absorption cell that has been measured using 3.2.34 path length, n—the distance that the sample gas
either a laser or other suitably accurate physical measurement
interacts with the infrared radiation.
device.
3.2.35 peak-to-peak noise, n—the absolute difference from
3.2.22 infrared spectrum, n—thatportionoftheelectromag- the highest positive peak to the lowest negative peak in a
–1
netic spectrum that spans the region from about 10 cm to
defined spectral region.
–1
about 12 500 cm . It is divided (6) into (1) the near-infrared
3.2.36 reference library—the available reference spectra for
–1
region (from 12 500 to 4000 cm ), (2) the mid-infrared region
use in developing the analytical algorithm.
–1
(from 4000 to 650 cm ), and (3) the far-infrared region (from
3.2.37 reference spectra, n—spectra of the absorbance ver-
–1
650 to 10 cm ).
sus wave number for a pure sample of a set of gases. These
3.2.23 instrument function, n—the function superimposed
spectra are obtained under controlled conditions of pressure
on the actual absorption line shape by the instrument. This is
and temperature, pathlength, and known concentration. The
sometimes referred to as the slit function; a term taken from
spectra are used to obtain the unknown concentrations of gases
instruments that use slits to obtain resolution.
in stationary source effluent samples.
3.2.24 instrument specific reference spectra, n—reference
3.2.38 resolution, n—the minimum separation that two
spectra collected on the instrument that collects the actual
spectral features can have and still, in some manner, be
sample spectra. The instrument specific reference spectra are
distinguished from one another.Acommonly used requirement
used in the analytical algorithm.
for two spectral features to be considered just resolved is the
Raleigh criterion.This states that two features are just resolved
3.2.25 intensity, n—the radiant power per unit solid angle.
when the maximum int
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