ASTM_E_1944_-_98_2013.pdf

Designation:E194498(Reapproved 2013)Standard Practice forDescribing and Measuring Performance of LaboratoryFourier Transform Near-Infrared(FT-NIR)Spectrometers:Level Zero and Level One Tests1This standard is issued under the fixed designation E1944;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.1.Scope1.1 This practice covers two levels of tests to measure theperformance of laboratory Fourier transform near infrared(FT-NIR)spectrometers.This practice applies to the short-wave near infrared region,approximately 800 nm(12 500 cm-1)to 1100 nm(9090.91 cm-1);and the long-wavelength nearinfrared region,approximately 1100 nm(9090.91 cm-1)to2500 nm(4000 cm-1).This practice is intended mainly fortransmittance measurements of gases and liquids,although it isbroadly applicable for reflectance measurements.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.2.Referenced Documents2.1 ASTM Standards:2E131 Terminology Relating to Molecular SpectroscopyE168 Practices for General Techniques of Infrared Quanti-tative AnalysisE932 Practice for Describing and Measuring Performance ofDispersive Infrared SpectrometersE1252 Practice for General Techniques for Obtaining Infra-red Spectra for Qualitative AnalysisE1421 Practice for Describing and Measuring Performanceof Fourier Transform Mid-Infrared(FT-MIR)Spectrom-eters:Level Zero and Level One Tests3.Terminology3.1 For definitions of terms used in this practice,refer toTerminology E131.All identifications of spectral regions andabsorbance band positions are given in nanometers(nm),andwavenumbers(cm-1);and spectral energy,transmittance,reflectance,and absorbance are signified by the letters E,T,Rand A respectively.A subscripted number signifies a spectralposition in nanometers,with wavenumbers in parenthesis(forexample,A1940(5154.64),denotes the absorbance at 1940 nm or5154.64 cm-1).4.Significance and Use4.1 This practice permits an analyst to compare the generalperformance of a laboratory instrument on any given day withthe prior performance of that instrument.This practice is notintended for comparison of different instruments with eachother,nor is it directly applicable to dedicated process FT-NIRanalyzers.This practice requires the use of a check samplecompatible with the instrument under test as described in 5.3.5.Test Conditions5.1 Operating ConditionsIn obtaining spectrophotometricdata for the check sample,the analyst must select the properinstrumental operating conditions in order to realize satisfac-tory instrument performance.Operating conditions for indi-vidual instruments are best obtained from the manufacturersinstructional literature due to the variations with instrumentdesign.It should be noted that many FT-NIR instruments aredesigned to work best if left in standby mode when they are notin use.A record should be kept to document the operatingconditions selected during a test so that they can be duplicatedfor future tests.Note that spectrometers are to be tested onlywithin their respective recommended measurement wavelength(wavenumber)ranges.5.2 Instrumental characteristics can influence these mea-surements in several ways.Vignetting of the beam(that is,theaperture of the sample cell is smaller than the diameter of thenear infrared beam at the focus)reduces the transmittancevalue measured in nonabsorbing regions,and on most instru-ments can change the apparent wavelength(or wavenumber)scale by a small amount,usually less than 0.01 nm(0.1 cm-1).1This 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 1998.Last previous edition approved in 2007 as E1944 98(2007).DOI:10.1520/E1944-98R13.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 Focus changes can also change transmittance values,so thesample should be positioned in the same location in the samplecompartment for each measurement.The angle of acceptance(established by the f number)of the optics between the s