1、Designation: E932 89 (Reapproved 2013)Standard Practice forDescribing and Measuring Performance of DispersiveInfrared Spectrometers1This standard is issued under the fixed designation E932; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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 practice covers the necessary information toqualify dispersive infrared instruments for specif
3、ic analyticalapplications, and especially for methods developed by ASTMInternational.1.2 This practice is not to be used as a rigorous test ofperformance of instrumentation.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4
4、 This standard does not purport to address all of thesafety problems, 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 applica-bility of regulatory limitations prior to use.2. Referenced Docu
5、ments2.1 ASTM Standards:2E131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE387 Test Method for Estimating Stray Radiant Power Ratioof Dispersive Spectrophotometers by the Opaque FilterMethodE1252 Practice for General Technique
6、s for Obtaining Infra-red Spectra for Qualitative Analysis3. Terminology3.1 Definitions and SymbolsFor definitions of terms andsymbols, refer to Terminology E131 and Compilation of ASTMStandard Definitions.34. Significance and Use4.1 This practice is intended for all infrared spectroscopistswho are
7、using dispersive instruments for qualitative or quan-titative areas of analysis.4.2 The purpose of this practice is to set forth performanceguidelines for testing instruments used in developing ananalytical method. These guidelines can be used to compare aninstrument in a specific application with t
8、he instrument(s) usedin developing the method.4.3 An infrared procedure must include a description of theinstrumentation and of the performance needed to duplicate theprecision and accuracy of the method.5. Apparatus5.1 For the purposes of this practice, dispersive instrumentsinclude those employing
9、 prisms, gratings, or filters to separateinfrared radiation into its component wavelengths.5.2 For each new method, describe the apparatus andinstrumentation both physically and mechanically, and also interms of performance as taught in this practice. That is, thedescription should give numerical va
10、lues showing the fre-quency accuracy and the frequency and the photometricprecision. State the spectral slit width maximum or slit widthprogram if one is used.Where possible, state the maximum andminimum resolution if those data are a part of the instrumentdisplay. Show typical component spectra as
11、produced by theinstrument to establish the needed resolution.5.3 If a computer program is used, describe the program.Include the programming language and availability, or whetherthe program is proprietary to a manufacturer.6. Reference to this Practice in Standards6.1 Reference to this practice shou
12、ld be included in allASTM infrared methods. The reference should appear in thesection on apparatus where the particular spectrometer isdescribed.1This practice is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility of Subcom-m
13、ittee E13.03 on Infrared and Near Infrared Spectroscopy.Current edition approved Jan. 1, 2013. Published January 2013. Originallyapproved in 1989. Last previous edition approved in 2007 as E932 89 (2007).DOI: 10.1520/E0932-89R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, o
14、rcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from ASTM International Headquarters, 100 Barr Harbor Drive, POBox C700, West Conshohocken, PA 19428.Copyright ASTM Inter
15、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17. Parameters in Spectroscopy7.1 Dispersive infrared spectrometers have a source ofquasi-monochromatic radiation together with a photometer formeasuring relative radiant power. Accurate spectrometry in-volv
16、es a large number of interrelated factors that determine thequality of the radiant power passing through a sample and thesensitivity and linearity with which this radiant power can bemeasured. Assuming proper instrumentation and its use, theinstrumental factors responsible for inaccuracies in spectr
17、om-etry are resolution, linearity (Practices E168), stray radiantpower (Test Method E387), and cell constants (PracticeE1252). Rigorous measurement of these factors is beyond thescope of this practice, and a more practical approach isdescribed for the accessible factors.8. Instrument Operation8.1 Th
18、e analyst selects the proper instrumental operatingconditions in order to get satisfactory performance (1-3).4Because instrument design varies, the manufacturers recom-mendations are usually best. A record of operating conditionsshould be kept so that data can be duplicated by future users.8.2 In ad
19、dition to operating conditions, the following shouldbe checked and recorded:8.2.1 Ambient temperature,8.2.2 Pen response time,8.2.3 Scanning speed,NOTE 1In some instruments these functions are integrated in the scanmodes.8.2.4 Noise level, and8.2.5 Mechanical repeatability.8.3 Each of the above fact
20、ors is important in the measure-ment of analytical wavenumber and photometric data. There isusually some lag between the recorded reading and the correctreading. Proper selection of operating conditions and good,reproducible, sample handling techniques minimize these ef-fects or make the effects rep
21、eatable. For example:8.3.1 Variation in temperature of the monochromator orsample may cause changes in wavenumber precision andaccuracy.8.3.2 Scanning too fast will displace the apparent wavenum-ber towards the direction scanned and will decrease the peakabsorbance reading for each band.NOTE 2Some i
22、nstruments provide for automatic monitoring andcorrection of this effect.8.4 Mechanical repeatability of the monochromator andrecording system as well as positioning of chart paper areimportant in wavenumber measurement.8.4.1 Chart paper should be checked for uniformity of theprinted scale length as
23、 received and rechecked at time of use,particularly if the paper has been subjected to pronouncedhumidity changes. Instructions on obtaining proper mechanicalrepeatability may be given in the manufacturers literature.8.5 In the case of computerized dispersive instruments, anyspectrum printed from a
24、computer file must be obtained asprescribed by the manufacturer and should be identical to theoriginal data.PRECISION AND ACCURACY9. Definitions9.1 wavenumber precisiona measure of the capability of aspectrometer to return to the same spectral position as mea-sured by a well-defined absorption or em
25、ission band when theinstrument is reset or rescanned. The index used in this practiceis the standard deviation.9.2 wavenumber accuracythe deviation of the averagewavenumber reading of an absorption band or emission bandfrom the known wavenumber of that band.10. Nature of Test10.1 For the purpose of
26、calibration, most methods employpure compounds and known mixtures at specified analyticalwavenumbers. The wavenumbers are either read from a dial,optical display, chart paper, or a computer file.11. Reference Wavenumbers in the Infrared Region (2)11.1 The recommended wavenumber calibration points ar
27、ethe absorption maxima of a standard (98.4/0.8/0.8 by weight)indene/camphor/cyclohexanone mixture listed in Table 1. Suit-able path lengths are 0.2 mm for the range from 3800 to 1580cm1and 0.03 mm for the wavenumber range from 1600 to 600cm-1. A mixture containing equal parts by weight of indene,cam
28、phor, and cyclohexanone (1/1/1 by weight) at a path length4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.TABLE 1 Indene-Camphor-Cyclohexanone (98.4/0.8/0.8) MixtureRecommended Calibration BandsNOTE 1Table 1 and Table 2 contain wavenumber values for band
29、s inFig. 1.BandNo.Wavenumber,cm1BandNo.Wavenumber,cm11 3927.2 1.0 44 1741.92 3901.6 44 1713.43 3798.9 47 1661.85 3660.6 1.0 48 1609.88 3297.8 1.0 49 1587.59 3139.5 51 1553.210 3110.2 53 1457.3 1.012 3025.4 54 1393.515 2887.6 55 1361.117 2770.9 57 1312.419 2673.3 58 1288.020 2622.3 60 1226.221 2598.4
30、 1.0 61 1205.123 2525.5 62 1166.128 2305.1 64 1122.429 2271.4 66 1067.7 1.030 2258.7 67 1018.533 2172.8 69 947.234 2135.8 1.0 70 942.435 2113.2 71 914.736 2090.2 72 861.339 1943.1 73 830.540 1915.3 74 765.341 1885.1 76 718.142 1856.9 77 692.6 1.044 1797.7 1.0E932 89 (2013)2of 0.1 mm may be used for
31、the range from 600 to 300 cm1.See Table 2 and Fig. 1.11.2 Polystyrene is also a convenient calibration standardfor the wavenumber range from 4000 to 400 cm1. Polystyrenefilms, approximately 0.03 to 0.05 mm thick, can be purchasedfrom instrument manufacturers. The recommended calibrationpeaks are lis
32、ted in Fig. 2.NOTE 3The correction of frequency for the refractive index of air issignificant in the wavenumber calculation only when wavelengths havebeen measured to better than 3 parts in 10 000. Reference (3) tabulatesadditional reference wavenumbers of interest.11.3 For low-resolution prism or f
33、ilter instruments operatedin single-beam mode, the position of the atmospheric carbondioxide band near 2350 cm1can be useful. This band may beresolved into a doublet. The 2350-cm1value is for theapproximate center between the two branches. The atmo-spheric carbon dioxide band near 667 cm1is useful i
34、n thelow-wavenumber region.12. Dynamic Error Test12.1 For dispersively measured spectra, the following dy-namic error test is suitable for use with most grating and prismspectrometers. (4 and 5)12.2 The spectrum of the (98.4/0.8/0.8) indene/camphor/cyclohexanone mixture is remeasured from 1350 to 85
35、0 cm1at one fourth of the scan rate used for the reference spectrumand with other operating conditions unchanged. The heightsfrom the baseline of the bands at 1288.0, 1226.2, 1205.1,1018.5 and 914.7 cm1are measured in absorbance units onboth the fast and slowly scanned charts. The absorbance ratiosA
36、1226.2/A1288.0, A1205.1/A1226.2, and A914.7/A1018.5should not differ by more than 60.02 between the fast andslow runs.NOTE 4The indene/camphor/cyclohexanone should remain in sealed,refrigerated ampoules.13. Selection of Slit Width or Slit Program13.1 One of the most important parameters the analyst
37、mustselect is the spectral slit width. The slit width affects resolutionand the signal-to-noise ratio (S/N). Generally, a narrower slitwidth gives higher resolution and lower S/N ratio. These mustbe optimized for any given analysis.13.2 The preferred manner of expressing resolution is interms of spe
38、ctral band width, but methods of measuring thisquantity in all spectral regions are not available.13.2.1 Spectral band width is not constant throughout thespectrum and therefore must be determined in each region ofinterest. In the neighborhood of 1200 cm1, the spectral bandwidth can be determined ap
39、proximately from the ratioA1205.1/A1226.2 of the (98.4/0.8/0.8) indene/camphor/cyclohexanone mixture, computed in the dynamic error test, asgiven in Table 3.13.3 In each infrared method, typical spectra of thecomponents, or a spectrum of a suitable mixture ofcomponents, should be included to illustr
40、ate the resolutionfound to be adequate to perform the analysis. These spectrashould be direct copies of the plotted spectra and not redrawncurves.PHOTOMETRY14. Linearity of Absorbance14.1 In a spectrometric method, photometric data are usedto determine concentrations. Linearity of absorbance is afun
41、ction of instrument response. The relationship must bedetermined in the concentration range of interest.14.2 Procedure for testing linearity and establishing work-ing curves are described in Practices E168.14.3 Some methods for quantitative analysis do not requirelinear response. The ultimate criter
42、ion for these is whether amethod gives correct answers for known samples.15. Measurement Procedure for Frequency Accuracy andPrecision15.1 From Tables 1-3, select calibration wavenumbers,preferably bracketing each analytical wavenumber and readeach wavenumber ten times.15.2 Average the observed read
43、ings for each wavenumber.The wavenumber accuracy is the difference between the truewavenumber and the average observed wavenumber.NOTE 5To check the wavenumber accuracy of a non-scanninginstrument, balance the instrument at the true value of the absorbancemaximum. Adjust the wavenumber drive until m
44、aximum apparent absor-bance is found.Always approach the line or band from the same direction.Repeat ten times.15.3 Calculate the precision of each observed wavenumberusing the following equation:s 5(Xi2 X!2n 2 1(1)where:s = estimated standard deviation of the series of results,Xi= individual observ
45、ed value (wavenumber, absorbance, ortransmittance)X= average (arithmetic mean) of the observed values, andn = number of observations.15.4 Results should be specified in the following order: truepeak position of reference material, average wavenumberdetermined, and wavenumber standard deviation.TABLE
46、 2 Indene-Camphor- Cyclohexanone (1/1/1) MixtureRecommended Calibration BandsNOTE 1Table 1 and Table 2 contain wavenumber values for bands inFig. 1.Band No.Wavenumber,cm11 592.12 551.73 521.44 490.2 1.05 420.56 393.17 381.68 301.4E932 89 (2013)316. Measurement Procedure for Photometric Precision16.1
47、 Photometric precision represents the capability of thephotometer system to reproduce the same value in successivedeterminations. The index of precision used in this practice isthe standard deviation.16.2 Photometric precision is determined on a calibrationsample by measuring the absorbance or trans
48、mittance of thesame sample ten times, following the same procedure used toobtain the data for the linearity test.16.3 Tabulate the individual readings of apparent absor-bance or transmittance. Calculate the standard deviation of theten readings using the equation in 15.3. Report the averagereading a
49、nd the standard deviation.17. Stray Radiate Power17.1 Stray radiant power (SRP) causes an error in thespectrometer zero transmittance reading. If measured at thedesignated path lengths, the indene/camphor/cyclohexanoneNOTE 1See Table 1 and Table 2 for cm1of numbered absorption maxima.FIG. 1 IUPAC Definitive Spectra of Indene-Camphor-Cyclohexanone Mixtures: A-C, 98.4/0.8/0.8 mixture; D, 1/1/1. (5)E932 89 (2013)4reference spectrum should show essentially zero transmittanceat 3050.0, 1609.6 and 765.4 cm1. The test spectra at th
