ASTM_E_1252_-_98_2013e1.pdf

Designation:E125298(Reapproved 2013)1Standard Practice forGeneral Techniques for Obtaining Infrared Spectra forQualitative Analysis1This standard is issued under the fixed designation E1252;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 parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEWarning statements were editorially corrected in January 2013.1.Scope1.1 This practice covers the spectral range from 4000 to 50cm1and includes techniques that are useful for qualitativeanalysis of liquid-,solid-,and vapor-phase samples by infraredspectrometric techniques for which the amount of sampleavailable for analysis is not a limiting factor.These techniquesare often also useful for recording spectra at frequencies higherthan 4000 cm1,in the near-infrared region.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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 limitations prior to use.Specific precau-tions are given in 6.5.1.2.Referenced Documents2.1 ASTM Standards:2E131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE334 Practice for General Techniques of Infrared Micro-analysisE573 Practices for Internal Reflection SpectroscopyE932 Practice for Describing and Measuring Performance ofDispersive Infrared SpectrometersE1421 Practice for Describing and Measuring Performanceof Fourier Transform Mid-Infrared(FT-MIR)Spectrom-eters:Level Zero and Level One TestsE1642 Practice for General Techniques of Gas Chromatog-raphy Infrared(GC/IR)Analysis3.Terminology3.1 DefinitionsFor definitions of terms and symbols,referto Terminology E131.4.Significance and Use4.1 Infrared spectroscopy is the most widely used techniquefor identifying organic and inorganic materials.This practicedescribes methods for the proper application of infraredspectroscopy.5.General5.1 Infrared(IR)qualitative analysis is carried out byfunctional group identification(1-3)3or by the comparison ofIR absorption spectra of unknown materials with those ofknown reference materials,or both.These spectra are obtained(4-8)through transmission,reflection,and other techniques,such as photoacoustic spectroscopy(PAS).Spectra that are tobe compared should be obtained by the same technique andunder the same conditions.Users of published referencespectra(9-16)should be aware that not all of these spectra arefully validated.5.1.1 Instrumentation and accessories for infrared qualita-tive analysis are commercially available.The manufacturersmanual should be followed to ensure optimum performanceand safety.5.2 Transmission spectra are obtained by placing a thinuniform layer of the sample perpendicular to the infraredradiation path(see 9.5.1 for exception in order to eliminateinterference fringes for thin films).The sample thickness mustbe adequate to cause a decrease in the radiant power reachingthe detector at the absorption frequencies used in the analysis.For best results,the absorbance of the strongest bands shouldbe in the range from 1 to 2,and several bands should have1This practice is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and Separation Science and is the direct responsibility of Subcom-mittee E13.03 on Infrared and Near Infrared Spectroscopy.Current edition approved Jan.1,2013.Published January 2013.Originallyapproved in 1988.Last previous edition approved in 2007 as E1252 98(2007).DOI:10.1520/E1252-98R13.2For 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.3The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 absorbances of 0.6 units or more.There are exceptions to thisgeneralization based on the polarity of the molecules beingmeasured.For example,saturated hydrocarbons are nonpolar,and their identifying bands are not strong enough unless theC-H stretch at 2920 cm1is opaque and the deformation bandsare in the range from 1.5 to 2.0 absorbance units(A)at 1440to 1460 cm 1.Spectra with different amounts of sample in theradiation path may be required to permit reliable analysis.Ifspectra are to be identified by computerized curve matching,the absorbance of the strongest band should be less than 1;otherwise,the effect of the instrument line shape function willcause errors in the