ASTM E1790-2004 Standard Practice for Near Infrared Qualitative Analysis《近红外线定性分析的标准规程》.pdf
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1、Designation: E 1790 04Standard Practice forNear Infrared Qualitative Analysis1This standard is issued under the fixed designation E 1790; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parent
2、heses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the use of near-infrared (NIR)spectroscopy for the qualitative analysis of liquids and solids.The practice is written under the a
3、ssumption that most NIRqualitative analyses will be performed with instruments de-signed specifically for this region and equipped with comput-erized data handling algorithms. In principle, however, thepractice also applies to work with liquid samples usinginstruments designed for operation over the
4、 ultraviolet (UV),visible, and mid-infrared (IR) regions if suitable data handlingcapabilities are available. Many Fourier Transform Infrared(FTIR) (normally considered mid-IR instruments) have NIRcapability, or at least extended-range beamsplitters that allowoperation to 1.2 m; this practice also a
5、pplies to data fromthese instruments.1.2 This standard does not purport to address all of thesafety concerns, 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 lim
6、itations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 131 Terminology Relating to Molecular SpectroscopyE 1252 Practice for General Techniques for Obtaining In-frared Spectra for Qualitative AnalysisE 1655 Practices for Infrared, Multivariate, QuantitativeAnalysis3. Terminology3.1 Defin
7、itionsFor definitions of general terms and sym-bols pertaining to NIR spectroscopy and statistical computa-tions, refer to Terminology E 131.3.2 Definitions of Terms Specific to This Standard:3.2.1 interactance, nthe phenomenon whereby radiantenergy entering the surface of a material is scattered by
8、 thematerial back to the surface, but at a different portion of thesurface.3.2.1.1 DiscussionThis differs from diffuse reflectance,where the returning radiation exits the same portion of thesurface of the material as the illuminating radiation entered.3.2.2 training sample (otherwise called a “refer
9、encesample” or “standard”), na quantity of material of knowncomposition or properties, or both, presented to an instrumentfor measurement in order to find relationships between themeasurements and the composition or properties, or both, ofthe sample.3.2.2.1 DiscussionThis term is typically used in c
10、onjunc-tion with computerized methods for ascertaining the relation-ships.Training samples for quantitative analysis (also called “calibrationsamples,” as in Practices E 1655) have different requirements thantraining samples used for qualitative analysis.4. Significance and Use4.1 NIR spectroscopy i
11、s a widely used technique for quan-titative analysis, and it is also becoming more widely used forthe identification of organic materials, that is, qualitativeanalysis. In general, however, the concept of qualitative analy-sis as used in the NIR spectral region differs from that used inthe mid-IR sp
12、ectral region in that NIR qualitative analysisrefers to the process of automated comparison of the spectra ofunknown materials to the spectra of known materials in orderto identify the unknown. This approach constitutes a librarysearch method in which each user generates his own library.4.2 Historic
13、ally, NIR spectroscopy as practiced with classi-cal UV-VIS-NIR instruments using methods similar to thosedescribed in Practice E 1252 was not considered to be a strongtechnique for qualitative analysis. Although the positions andintensities of absorption bands in specific wavelength rangeswere used
14、to confirm the presence of certain functional groups,the spectra were not considered to be specific enough to allowunequivocal identification of unknown materials. A few impor-tant libraries of NIR spectra were developed for qualitativepurposes, but the lack of suitable data handling facilities1This
15、 practice is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and Chromatography and is the direct responsibility of SubcommitteeE13.11 on Chemometrics.Current edition approved Nov. 1, 2004. Published December 2004. Originallyapproved in 1996. Last previous edition approved in 2
16、000 as E 1790 00.2For 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 Harb
17、or Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.limited the scope of qualitative analysis severely. Furthermore,earlier work was limited almost entirely to liquid samples.4.3 Currently, the mid-IR procedure of deducing the struc-ture of an unknown material via analysis of the
18、locations,strengths, and positional shifts of individual absorption bandsis generally not used in the NIR.4.4 With the development of specialized NIR instrumentsand mathematical algorithms for treating the data, it becamepossible to obtain a wealth of information from NIR spectrathat had hitherto go
19、ne unused. While the mathematical algo-rithms described in this practice can be applied to spectral datain any region, this practice describes their application to theNIR.4.5 The application of NIR spectroscopy to qualitativeanalysis in the manner described is relatively new, and proce-dures for thi
20、s application are still evolving. The application ofchemometric methods to spectroscopy has limitations, and thelimitations are not all defined yet since the techniques arerelatively new. One area of concern to some scientists is theeffect of low-level contaminants. Any analytical methodologyhas its
21、 detection limits, and NIR is no different in this regard,but neither would we expect it to be any worse. Since therelatively broad character of NIR bands makes it unlikely thata contaminant would not overlap any of the measured wave-lengths, the question would only be one of degree: whether agiven
22、amount of contaminant could be detected. The user mustbe aware of the probable contaminants he is liable to run intoand account for the possibility of this occurring, perhaps byincluding deliberately contaminated samples in the training set.5. General5.1 NIR qualitative analysis is conducted by comp
23、arison ofNIR absorption spectra of unknown materials with those ofknown reference materials. Since the absorption bands of manysubstances of interest are less distinctive in the NIR than in themid-IR spectral region, the analytical capability of the tech-nique relies heavily on the accuracy of the a
24、bsorption mea-surements and the relationship of the relative absorbances atdifferent wavelengths. Materials to be identified are measuredby a NIR spectrometer, and the spectral data thus generated aresaved in an auxiliary computer attached to the spectrometerproper. One of the several algorithms des
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