1、Designation: E 2056 04Standard Practice forQualifying Spectrometers and Spectrophotometers for Usein Multivariate Analyses, Calibrated Using SurrogateMixtures1This standard is issued under the fixed designation E 2056; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice relates to the multivariate calibration ofspectrometers
3、 and spectrophotometers used in determining thephysical and chemical characteristics of materials. A detaileddescription of general multivariate analysis is given in PracticeE 1655. This standard refers only to those instances wheresurrogate mixtures can be used to establish a suitable calibra-tion
4、matrix. This practice specifies calibration and qualificationdata set requirements for interlaboratory studies (ILSs), that is,round robins, of standard test methods employing surrogatecalibration techniques that do not conform exactly to PracticesE 1655.NOTE 1For some multivariate spectroscopic ana
5、lyses, interferencesand matrix effects are sufficiently small that it is possible to calibrate usingmixtures that contain substantially fewer chemical components than thesamples that will ultimately be analyzed. While these surrogate methodsgenerally make use of the multivariate mathematics describe
6、d in PracticesE 1655, they do not conform to procedures described therein, specificallywith respect to the handling of outliers.1.2 This practice specifies how the ILS data is treated toestablish spectrometer/spectrophotometer performance qualifi-cation requirements to be incorporated into standard
7、testmethods.NOTE 2Spectrometer/spectrophotometer qualification procedures areintended to allow the user to determine if the performance of a specificspectrometer/spectrophotometer is adequate to conduct the analysis so asto obtain results consistent with the published test method precision.1.2.1 The
8、 spectroscopies used in the surrogate test methodswould include but not be limited to mid- and near-infrared,ultraviolet/visible, fluorescence and Raman spectroscopies.1.2.2 The surrogate calibrations covered in this practice are:multilinear regression (MLR), principal components regression(PCR) or
9、partial least squares (PLS) mathematics. Thesecalibration procedures are described in detail in PracticesE 1655.1.3 For surrogate test methods, this practice recommendslimitations that should be placed on calibration options that areallowed in the test method. Specifically, this practice recom-mends
10、 that the test method developer demonstrate that allcalibrations that are allowed in the test method producestatistically indistinguishable results.1.4 For surrogate test methods that reference spectrometer/spectrophotometer performance practices, such as PracticesE 275, E 387, E 388, E 579, E 925,
11、E 932, E 958, E 1421,E 1683, E 1866 or E 1944, this practice recommends thatinstrument performance data be collected as part of the ILS toestablish the relationship between spectrometer/spectrophotometer performance and test method precision.2. Referenced Documents2.1 ASTM Standards:2D 6277 Test Met
12、hod for Determination of Benzene inSpark-Ignition Engine Fuels Using Mid Infrared Spectros-copyD 6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsE 131 Terminology Relating to Molecular SpectroscopyE 275 Practice for Describing and
13、 Measuring Performanceof Ultraviolet, Visible, and Near Infrared Spectrophotom-etersE 387 Test Method for Estimating Stray Radiant PowerRatio of Dispersive Spectrophotometers by the OpaqueFilter MethodE 388 Test Method for Spectral Bandwidth and WavelengthAccuracy of Fluorescence SpectrometersE 579
14、Test Method for Limit of Detection of Fluorescenceof Quinine Sulfate in SolutionE 691 Practice for Conducting an Inter-Laboratory Study toDetermine the Precision of a Test MethodE 925 Practice for Monitoring the Calibration of UltravioletVisible Spectrophotometers Whose Spectral Slit Width1This prac
15、tice is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and is the direct responsibility of Subcommittee E13.11 on Chemo-metrics.Current edition approved Nov. 1, 2004. Published December 2004. Originallyapproved in 1999. Last previous edition approved in 2000 as E 2056 00.2For
16、referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
17、 West Conshohocken, PA 19428-2959, United States.Does Not Exceed 2nmE 932 Practice for Describing and Measuring Performanceof Dispersive Infrared SpectrometersE 958 Practice for Measuring Practical Spectral Bandwidthof Ultraviolet-Visible SpectrophotometersE 1421 Practice for Describing and Measurin
18、g Performanceof Fourier Transform Mid-Infrared (FT-MIR) Spectropho-tometers: Level Zero and Level One TestsE 1655 Practices for Infrared, Multivariate, QuantitativeAnalysisE 1683 Practice for Testing the Performance of ScanningRaman SpectrometersE 1866 Guide for Establishing Spectrophotometer Perfor
19、-mance TestsE 1944 Practice for Describing and Measuring Performanceof Laboratory Fourier Transform Near-Infrared (FT-MIR)Spectrometers: Level Zero and Level One Tests3. Terminology3.1 Definitions:3.1.1 For definitions of terms and symbols relating toinfrared, ultraviolet/visible and Raman spectrosc
20、opy, refer toTerminology E 131.3.1.2 For definitions of terms and symbols relating tomultivariate analysis, refer to Practices E 1655.3.2 Definitions of Terms Specific to This Standard:3.2.1 spectrometer/spectrophotometer qualification, ntheprocedures by which a user demonstrates that the performanc
21、eof a specific spectrometer/spectrophotometer is adequate toconduct a multivariate analysis so as to obtain precisionconsistent with that specified in the test method.3.2.2 surrogate calibration, na multivariate calibrationthat is developed using a calibration set which consists ofmixtures with pre-
22、specified and reproducible compositions thatcontain substantially fewer chemical components than thesamples that will ultimately be analyzed.3.2.3 surrogate test method, na standard test method thatis based on a surrogate calibration.4. Summary of Practice4.1 Asurrogate test method must specify the
23、composition oftwo sets of samples. One set is used to calibrate thespectrometers/spectrophotometers. The second set of samplesis used to qualify the spectrometer/spectrophotometer to per-form the analysis. The compositions of both sets are expressedin terms of weight or volume fraction depending on
24、whetherthe samples are prepared gravimetrically or volumetrically. Thecompositions of both sets should be specified in the surrogatetest method. If the surrogate test method is being used toestimate a physical property, then the test method shouldindicate what value of the property is to be assigned
25、 to each ofthe calibration and qualification samples.4.2 The surrogate test method should specify the minimumspectrometer/spectrophotometer requirements for instrumentsthat can be used to perform the test method.4.3 The spectrometer/spectrophotometer test method shouldspecify the exact conditions th
26、at are to be used to collect and,where appropriate, to calculate the spectral data used in thecalibration and analysis.4.4 The test method should specify the exact mathematicsthat are to be used to develop the multivariate calibration.Allowable spectral preprocessing methods should be defined.The sp
27、ecific mathematics (MLR, PCR or PLS) should bespecified, and the acceptable range for the numbers of variablesshould be given.4.5 When the ILS is conducted to establish the precision ofthe surrogate test method, the calibration data for all of theparticipating laboratories should be collected and us
28、ed tocalculate a pooled standard error of calibration for the testmethod. The pooled standard error of calibration and itsassociated degrees of freedom should be reported in the testmethod.4.5.1 When a user is calibrating a spectrometer/spectrophotometer, the standard error of calibration is calcu-l
29、ated and compared to the pooled standard error of calibrationfrom the ILS to determine if the performance of the calibratedspectrometer/spectrophotometer is adequate to produce analy-ses of the precision specified in the test method.4.5.2 If a user is purchasing a precalibrated spectrometer/spectrop
30、hotometer, the instrument vendor should supply thestandard error of calibration and its statistical comparison tothe pooled standard error of calibration.4.6 During the ILS, each participating laboratory analyzes aset of qualification samples and reports both the compositionsof the qualification set
31、 and the estimates made using themultivariate analysis. A pooled error of qualification is calcu-lated and reported as part of the test method along with itscorresponding degrees of freedom.4.6.1 Before a user may use the spectrometer/spectrophotometer, it must be qualified to perform the surro-gate
32、 test method. The qualification set is analyzed, and astandard error of qualification is calculated. The standard errorof qualification is statistically compared with the pooledstandard error of qualification to determine if the performanceof the calibrated spectrometer/spectrophotometer is adequate
33、 toproduce analyses of the precision specified in the test method.4.6.2 Spectrometer/spectrophotometer qualification is re-quired regardless of whether the calibration is performed by thevendor or the user.4.6.3 Spectrometer/spectrophotometer qualification shouldbe repeated after major maintenance h
34、as been performed on thespectrometer/spectrophotometer so as to determine whetherrecalibration is required.5. Significance and Use5.1 This practice should be used by the developer ofstandard test methods that employ surrogate calibrations.5.1.1 This practice assists the test method developer insetti
35、ng and documenting requirements for the spectrometer/spectrophotometers that can perform the test method.5.1.2 This practice assists the test method developer insetting and documenting spectral data collection and compu-tation parameters for the test method.5.1.3 This practice assists the test metho
36、d developer inselecting among possible multivariate analysis procedures thatcould be used to establish the surrogate calibration. Thepractice describes statistical tests that should be performed toensure that all multivariate analysis procedures that are allowedE2056042within the scope of the test m
37、ethod produce statisticallyindistinguishable results.5.1.4 This practice describes statistical calculations that thetest method developer should perform on the calibration andqualification data that should be collected as part of the ILSthat establishes the test method precision. These calculationse
38、stablish the level of performance that spectrometers/spectrophotometers must meet in order to perform the testmethod.5.2 This practice describes how the person who calibrates aspectrometer/spectrophotometer can test the performance ofsaid spectrometer/spectrophotometer to determine if the per-forman
39、ce is adequate to conduct the test method.5.3 This practice describes how the user of a spectrometer/spectrophotometer can qualify the spectrometer/spectrophotometer to conduct the test method.6. Surrogate Calibrations6.1 Practices E 1655 assumes that the calibration set used todevelop a multivariat
40、e model contains samples of the sametype as those that are to eventually be analyzed using themodel. Practices E 1655 requires use of outlier statistics toensure that samples being analyzed are sufficiently similar tothe calibration samples to produce meaningful results. Forsome spectroscopic analys
41、es, however, it is possible to cali-brate using gravimetrically or volumetrically prepared mix-tures that contain significantly fewer components than thesamples that will ultimately be analyzed. For these surrogatetest methods, the outlier statistics described in Practices E 1655are not appropriate
42、since all samples are expected to be outliersrelative to the simplified calibrations. Thus, surrogate testmethods cannot fulfill the requirements of Practices E 1655.While surrogate test methods may make use of the mathemat-ics described in Practices E 1655, they should not claim tofollow the proced
43、ures described in that practice.6.1.1 In developing surrogate test methods, it is necessary tothoroughly understand and account for potential spectral inter-ferences. Typically, the spectral range used in surrogate cali-brations will be limited so as to minimize interferences. Forthose interferences
44、 that cannot be eliminated through limitingthe spectral range, representative components that mimic theinterference should be included in the calibration mixtures.6.1.2 Test Method D 6277 provides an example of a surro-gate test method. The FT-MIR analysis of benzene in gasolineis calibrated using m
45、ixtures of benzene, isooctane, toluene andxylenes and PLS mathematics. The calibration mixtures con-tain far fewer components than gasoline, but the spectral rangeused in the analysis is limited to a narrow range about arelatively interference-free benzene peak. Toluene and xylenesare used in the ca
46、libration mixtures to adequately mimic theinterferences that are present in gasolines.6.2 Calibration Sets:6.2.1 The sets of surrogate samples that are used to calibratethe spectrometers/spectrophotometers should satisfy the re-quirements of Practices E 1655.Ifk is the number of variables(MLR wavele
47、ngths or frequencies, PCR principal componentsor PLS latent variables) used in the model, then the minimumnumber of calibration samples should be the greater of 24 or6k. If the calibration set is derived from an experimentaldesign, and if the spectra have been shown to be linearfunctions of the comp
48、onent concentrations, then fewer calibra-tion samples can be used, but in all cases the minimum numberof calibration samples should be the greater of 24 or 4k. Theexperimental design must independently vary all componentsover the desired analysis range.6.2.2 When calibrating for a single component,
49、the calibra-tion set should uniformly span the range over which theanalysis of that component is to be conducted. Additionalcomponents that are present in the calibration set to simulateinterferences should be independently and uniformly variedover a range at least as large as is likely to be encounteredduring actual application of the test method.6.2.3 When calibrating for a property that depends on morethan one chemical component, the calibration set shoulduniformly span the range over which the property analysis is tobe conducted, and all components that contribute to theprope
