Standard Practice for Describing and Measuring Performance of Dispersive Infrared Spectrometers

SIGNIFICANCE AND USE
This practice is intended for all infrared spectroscopists who are using dispersive instruments for qualitative or quantitative areas of analysis.
The purpose of this practice is to set forth performance guidelines for testing instruments used in developing an analytical method. These guidelines can be used to compare an instrument in a specific application with the instrument(s) used in developing the method.
An infrared procedure must include a description of the instrumentation and of the performnace needed to duplicate the precision and accuracy of the method.
SCOPE
1.1This practice covers the necessary information to qualify dispersive infrared instruments for specific analytical applications, and especially for methods developed by ASTM International.
1.2 This practice is not to be used as a rigorous test of performance of instrumentation.
1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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Publication Date
30-Nov-2007
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E932 − 89 (Reapproved2007)
Standard Practice for
Describing and Measuring Performance of Dispersive
Infrared Spectrometers
This standard is issued under the fixed designation E932; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Significance and Use
4.1 This practice is intended for all infrared spectroscopists
1.1 This practice covers the necessary information to
who are using dispersive instruments for qualitative or quan-
qualify dispersive infrared instruments for specific analytical
titative areas of analysis.
applications, and especially for methods developed by ASTM
International.
4.2 The purpose of this practice is to set forth performance
guidelines for testing instruments used in developing an
1.2 This practice is not to be used as a rigorous test of
analyticalmethod.Theseguidelinescanbeusedtocomparean
performance of instrumentation.
instrumentinaspecificapplicationwiththeinstrument(s)used
1.3 This standard does not purport to address all of the
in developing the method.
safety problems, if any, associated with its use. It is the
4.3 An infrared procedure must include a description of the
responsibility of the user of this standard to establish appro-
instrumentationandoftheperformanceneededtoduplicatethe
priate safety and health practices and determine the applica-
precision and accuracy of the method.
bility of regulatory limitations prior to use.
5. Apparatus
2. Referenced Documents
5.1 For the purposes of this practice, dispersive instruments
2.1 ASTM Standards:
include those employing prisms, gratings, or filters to separate
E131Terminology Relating to Molecular Spectroscopy
infrared radiation into its component wavelengths.
E168Practices for General Techniques of Infrared Quanti-
5.2 For each new method, describe the apparatus and
tative Analysis
instrumentation both physically and mechanically, and also in
E387TestMethodforEstimatingStrayRadiantPowerRatio
terms of performance as taught in this practice. That is, the
of Dispersive Spectrophotometers by the Opaque Filter
description should give numerical values showing the fre-
Method
quency accuracy and the frequency and the photometric
E1252Practice for General Techniques for Obtaining Infra-
precision. State the spectral slit width maximum or slit width
red Spectra for Qualitative Analysis
programifoneisused.Wherepossible,statethemaximumand
minimum resolution if those data are a part of the instrument
3. Terminology
display. Show typical component spectra as produced by the
instrument to establish the needed resolution.
3.1 Definitions and Symbols—For definitions of terms and
symbols,refertoTerminologyE131and Compilation of ASTM
5.3 If a computer program is used, describe the program.
Standard Definitions.
Includetheprogramminglanguageandavailability,orwhether
the program is proprietary to a manufacturer.
6. Reference to this Practice in Standards
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
6.1 Reference to this practice should be included in all
mittee E13.03 on Infrared and Near Infrared Spectroscopy.
ASTM infrared methods. The reference should appear in the
Current edition approved Dec. 1, 2007. Published December 2007. Originally
approved in 1989. Last previous edition approved in 2002 as E932-89(2002).
section on apparatus where the particular spectrometer is
DOI: 10.1520/E0932-89R07.
described.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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 7. Parameters in Spectroscopy
the ASTM website.
7.1 Dispersive infrared spectrometers have a source of
Available from ASTM International Headquarters, 100 Barr Harbor Drive,
West Conshohocken, PA 19428. quasi-monochromatic radiation together with a photometer for
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E932 − 89 (2007)
measuring relative radiant power. Accurate spectrometry in- PRECISION AND ACCURACY
volvesalargenumberofinterrelatedfactorsthatdeterminethe
9. Definitions
quality of the radiant power passing through a sample and the
sensitivity and linearity with which this radiant power can be
9.1 wavenumber precision—ameasureofthecapabilityofa
measured. Assuming proper instrumentation and its use, the
spectrometer to return to the same spectral position as mea-
instrumental factors responsible for inaccuracies in spectrom-
sured by a well-defined absorption or emission band when the
etry are resolution, linearity (Practices E168), stray radiant
instrumentisresetorrescanned.Theindexusedinthispractice
power (Test Method E387), and cell constants (Practice
is the standard deviation.
E1252). Rigorous measurement of these factors is beyond the
9.2 wavenumber accuracy—the deviation of the average
scope of this practice, and a more practical approach is
wavenumber reading of an absorption band or emission band
described for the accessible factors.
from the known wavenumber of that band.
8. Instrument Operation
10. Nature of Test
8.1 The analyst selects the proper instrumental operating
10.1 For the purpose of calibration, most methods employ
conditions in order to get satisfactory performance (1-3).
pure compounds and known mixtures at specified analytical
Because instrument design varies, the manufacturer’s recom-
wavenumbers. The wavenumbers are either read from a dial,
mendations are usually best. A record of operating conditions
optical display, chart paper, or a computer file.
should be kept so that data can be duplicated by future users.
8.2 Inadditiontooperatingconditions,thefollowingshould
11. Reference Wavenumbers in the Infrared Region (2)
be checked and recorded:
11.1 The recommended wavenumber calibration points are
8.2.1 Ambient temperature,
the absorption maxima of a standard (98.4/0.8/0.8 by weight)
8.2.2 Pen response time,
indene/camphor/cyclohexanonemixturelistedinTable1.Suit-
8.2.3 Scanning speed,
able path lengths are 0.2 mm for the range from 3800 to 1580
−1
NOTE1—Insomeinstrumentsthesefunctionsareintegratedinthescan cm and0.03mmforthewavenumberrangefrom1600to600
-1
modes.
cm . A mixture containing equal parts by weight of indene,
camphor,andcyclohexanone(1/1/1byweight)atapathlength
8.2.4 Noise level, and
−1
of 0.1 mm may be used for the range from 600 to 300 cm .
8.2.5 Mechanical repeatability.
See Table 2 and Fig. 1.
8.3 Each of the above factors is important in the measure-
11.2 Polystyrene is also a convenient calibration standard
ment of analytical wavenumber and photometric data.There is
−1
forthewavenumberrangefrom4000to400cm .Polystyrene
usually some lag between the recorded reading and the correct
films, approximately 0.03 to 0.05 mm thick, can be purchased
reading. Proper selection of operating conditions and good,
reproducible, sample handling techniques minimize these ef-
fects or make the effects repeatable. For example:
8.3.1 Variation in temperature of the monochromator or
TABLE 1 Indene-Camphor-Cyclohexanone (98.4/0.8/0.8) Mixture—
sample may cause changes in wavenumber precision and
Recommended Calibration Bands
accuracy.
Band Wavenumber, Band Wavenumber,
−1 −1
8.3.2 Scanningtoofastwilldisplacetheapparentwavenum-
No. cm No. cm
ber towards the direction scanned and will decrease the peak 1 3927.2 ± 1.0 44α 1741.9
2 3901.6 44β 1713.4
absorbance reading for each band.
3 3798.9 47 1661.8
5 3660.6 ± 1.0 48 1609.8
NOTE 2—Some instruments provide for automatic monitoring and
8 3297.8 ± 1.0 49 1587.5
correction of this effect.
9 3139.5 51 1553.2
8.4 Mechanical repeatability of the monochromator and 10 3110.2 53 1457.3 ± 1.0
12 3025.4 54 1393.5
recording system as well as positioning of chart paper are
15 2887.6 55 1361.1
important in wavenumber measurement.
17 2770.9 57 1312.4
8.4.1 Chart paper should be checked for uniformity of the 19 2673.3 58 1288.0
20 2622.3 60 1226.2
printed scale length as received and rechecked at time of use,
21 2598.4 ± 1.0 61 1205.1
particularly if the paper has been subjected to pronounced
23 2525.5 62 1166.1
28 2305.1 64 1122.4
humiditychanges.Instructionsonobtainingpropermechanical
29 2271.4 66 1067.7 ± 1.0
repeatability may be given in the manufacturer’s literature.
30 2258.7 67 1018.5
33 2172.8 69 947.2
8.5 In the case of computerized dispersive instruments, any
34 2135.8 ± 1.0 70 942.4
spectrum printed from a computer file must be obtained as
35 2113.2 71 914.7
prescribed by the manufacturer and should be identical to the
36 2090.2 72 861.3
39 1943.1 73 830.5
original data.
40 1915.3 74 765.3
41 1885.1 76 718.1
42 1856.9 77 692.6 ± 1.0
The boldface numbers refer to the list of references at the end of this practice. 44 1797.7 ± 1.0
E932 − 89 (2007)
TABLE 2 Indene-Camphor- Cyclohexanone (1/1/1) Mixture—
A1205.1/A1226.2 of the (98.4/0.8/0.8) indene/camphor/
Recommended Calibration Bands
cyclohexanonemixture,computedinthedynamicerrortest,as
Wavenumber,
given in Table 3.
Band No.
−1
cm
13.3 In each infrared method, typical
...

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