ASTM E1944-98

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Designation: E 1944 – 98
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Describing and Measuring Performance of Laboratory
Fourier Transform Near-Infrared (FT-NIR) Spectrometers:
1
Level Zero and Level One Tests
This standard is issued under the fixed designation E 1944; 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 and A respectively. A subscripted number signifies a spectral
position in nanometers, with wavenumbers in parenthesis (for
1.1 This practice covers two levels of tests to measure the
example,
performance of laboratory Fourier transform near infrared
1940(5154.64)
A , denotes the absorbance at 1940 nm or 5154.64
(FT-NIR) spectrometers. This practice applies to the short-
-1
cm ).
wave near infrared region, approximately 800 nm (12 500
-1 -1
cm ) to 1100 nm (9090.91 cm ); and the long-wavelength
4. Significance and Use
-1
near infrared region, approximately 1100 nm (9090.91 cm )to
-1
4.1 This practice permits an analyst to compare the general
2500 nm (4000 cm ). This practice is intended mainly for
performance of a laboratory instrument on any given day with
transmittance measurements of gases and liquids, although it is
the prior performance of that instrument. This practice is not
broadly applicable for reflectance measurements.
intended for comparison of different instruments with each
1.2 The values stated in SI units are to be regarded as the
other, nor is it directly applicable to dedicated process FT-NIR
standard.
analyzers. This practice requires the use of a check sample
1.3 This standard does not purport to address all of the
compatible with the instrument under test as described in 5.3.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Test Conditions
priate safety and health practices and determine the applica-
5.1 Operating Conditions—In obtaining spectrophotometric
bility of regulatory limitations prior to use.
data for the check sample, the analyst must select the proper
2. Referenced Documents instrumental operating conditions in order to realize satisfac-
tory instrument performance. Operating conditions for indi-
2.1 ASTM Standards:
2 vidual instruments are best obtained from the manufacturer’s
E 131 Terminology Relating to Molecular Spectroscopy
instructional literature due to the variations with instrument
E 168 Practices for General Techniques of Infrared Quanti-
2 design. It should be noted that many FT-NIR instruments are
tative Analysis
designed to work best if left in standby mode when they are not
E 932 Practices for Describing and Measuring Performance
2 in use. A record should be kept to document the operating
of Dispersive Infrared Spectrometers
conditions selected during a test so that they can be duplicated
E 1252 Practice for General Techniques for Qualitative
2 for future tests. Note that spectrometers are to be tested only
Analysis
within their respective recommended measurement wavelength
E 1421 Practice for Describing and Measuring Performance
(wavenumber) ranges.
of Fourier Transform Infrared (FT-IR) Spectrometers:
2 5.2 Instrumental characteristics can influence these mea-
Level Zero and Level One Tests
surements in several ways. Vignetting of the beam (that is, the
3. Terminology aperture of the sample cell is smaller than the diameter of the
near infrared beam at the focus) reduces the transmittance
3.1 For definitions of terms used in this practice, refer to
value measured in nonabsorbing regions, and on most instru-
Terminology E 131. All identifications of spectral regions and
ments can change the apparent wavelength (or wavenumber)
absorbance band positions are given in nanometers (nm), and
-1
-1
scale by a small amount, usually less than 0.01 nm (0.1 cm ).
wavenumbers (cm ); and spectral energy, transmittance, re-
Focus changes can also change transmittance values, so the
flectance, and absorbance are signified by the letters E, T, R
sample should be positioned in the same location in the sample
compartment for each measurement. The angle of acceptance
1
This practice is under the jurisdiction of ASTM Committee E-13 on Molecular
(established by the f number) of the optics between the sample
Spectroscopy and is the direct responsibility of Subcommittee E 13.03 on Infrared
and detector significantly affects apparent transmittance. Heat-
Spectroscopy.
ing of the sample by the beam or by the higher temperatures
Current edition approved Mar
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