1、Designation: E1252 98 (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
2、 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 spe
3、ctral 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 recor
4、ding 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 it
5、s 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
6、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 SpectrometersE1
7、421 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, refer
8、to 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 byf
9、unctional 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 to
10、be 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 manu
11、facturersmanual 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 thi
12、ckness 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
13、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
14、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 number
15、s 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 States1absorbances of 0.6 units or more. There are exceptions to thisgeneralization based on the polarity of the molecu
16、les 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 cm1. Spectra with different amounts of sample
17、 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 relative intensities of band
18、s in spectrameasured by dispersive spectrometers and by FT-IR spectrom-eters with certain apodization functions (specially triangular).5.2.1 Techniques for obtaining transmission spectra varywith the sample state. Most samples, except free-standing thinfilms, require IR transparent windows or matric
19、es containingthe sample. Table 1 gives the properties of IR windowmaterials commonly employed. Selection of the window ma-terial depends on the region of the IR spectrum to be used foranalysis, on the absence of interference with the sample, andadequate durability for the sample type.5.3 Spectra obt
20、ained by reflection configurations commonlyexhibit both reflection and absorption characteristics and areaffected by the refractive indices of the media and the inter-faces. Spectral interpretation should be based on references rununder the same experimental conditions. In particular, it shouldbe re
21、alized that the spectrum of the surface of a samplerecorded by reflection will often differ from the spectrum of thebulk material as recorded by transmission spectroscopy. This isbecause the chemistry of the surface often differs from that ofthe bulk, due to factors such as surface oxidation, migrat
22、ion ofspecies from the bulk to the surface, and possible surfacecontaminants. Some surface measurements are extremely sen-sitive to small amounts of materials present on a surface,whereas transmission spectroscopy is relatively insensitive tothese minor components.5.3.1 Reflection spectra are obtain
23、ed in four configurations:5.3.1.1 Specular reflectance (7.5),5.3.1.2 Diffuse reflectance (7.6),5.3.1.3 Reflection-absorption (7.7),5.3.1.4 Internal reflection (7.9). Refer to Practices E573.This technique is also called Attenuated Total Reflection(ATR), and5.3.1.5 Grazing angle reflectance.5.4 Photo
24、acoustic IR spectra (11.2).5.5 Emission spectroscopy (11.4).TEST METHODS AND TECHNIQUES6. Analysis of Liquids6.1 Fixed CellsA wide range of liquid samples of low tomoderate viscosity may be introduced into a sealed fixed-pathlength cell. These are commercially available in a variety ofmaterials and
25、path lengths. Typical path lengths are 0.01 to 0.2mm. See 5.2 for considerations in selection of cell materialsand path lengths.6.2 Capillary FilmsSome liquids are too viscous to forceinto or out of a sealed cell. Examination of viscous liquids isaccomplished by placing one or more drops in the cent
26、er of aflat window. Another flat window is then placed on top of theliquid. Pressure is applied in order to form a bubble-freecapillary film covering an area large enough that the entireradiation beam passes through the film. The film thickness isregulated by the amount of pressure applied and the v
27、iscosityof the liquid. A capillary film prepared in this manner has apath length of about 0.01 mm. Volatile and highly fluidmaterials may be lost from films prepared in this manner.Demountable spacers can be used when a longer path length isrequired to obtain a useful spectrum.6.3 Internal Reflectio
28、n Spectroscopy (IRS)Viscous mate-rials can be smeared on one or both sides of an internalreflection element (IRE). See Practices E573 for detailedinformation on this technique.6.4 Disposable IR Cards4These can be used to obtainspectra of non-volatile liquids. A very small drop, usually lessthan 10 L
29、 of the liquid, is applied near the edge of the sampleapplication area. If the sample does not easily flow across thesubstrate surface, it may be spread using an appropriate tool.The sample needs to be applied in a thin layer, completelycovering an area large enough that the entire radiation beampas
30、ses through the sample. Note that any volatile componentsof a mixture will be lost in this process, which may make theuse of a disposable card a poor choice for such systems.6.5 Solution Techniques:6.5.1 Analysis of Materials Soluble in Infrared (IR) Trans-parent Solvent: The Split Solvent Technique
31、Many solid andliquid samples are soluble in solvents that are transparent inparts of the infrared spectral region. A list of solvents com-monly used in obtaining solution spectra is given in Table 2.The selection of solvents depends on several factors. Thesample under examination must have adequate
32、solubility, itmust not react with the solvent, and the solvent must haveappropriate transmission regions that enable a useful spectrumto be obtained. Combinations of solvents and window materi-als can often be selected that will allow a set of qualitativesolution-phase spectra to be obtained over th
33、e entire IR region.One example of this “split solvent” technique utilizes carbontetrachloride (CCl4) and carbon disulfide (CS2) as solvents.(WarningBoth CCl4and CS2are toxic; keep in a wellventilated hood. Use of these solvents is prohibited in manylaboratories. In addition, CS2is extremely flammabl
34、e; keepaway from ignition sources, even a steam bath. Moreover, CS2is reactive (sometimes violently) with primary and secondaryaliphatic amines and must not be used as a solvent for thesecompounds. Similarly, CCl4reacts with aluminum metal.Depending on conditions such as temperature and particle siz
35、e,the reaction has been lethally violent.)6.5.1.1 Absorption by CCl4is negligible in the region 4000to 1330 cm1and by CS2in the region 1330 to 400 cm1incells of about 0.1 mm thickness. (Other solvents can be used.)4The 3M disposable IR Card is manufactured by 3M Co., Disposable ProductsDivision.E125
36、2 98 (2013)12TABLE 1 Properties of Window Materials (in order of long-wavelength limit)Window MaterialChemicalCompositionCutoff RangeAUseful Transmission RangeWaterSolubilityRefractiveIndexat(;m)Remarks(m) (cm1) (m) (cm1)Glass SiO2+ ;2.5 ;4000 0.352 28 5705000 insoluble 1.51.9 HF, alkaliBQuartz (fus
37、ed) SiO2;3.5 ;2857 0.24 50 0002500 insoluble 1.43 4.5 HFBSIlicon Nitrate Si3N40.34.5 33 0002200Silicon Carbide SiC 0.65 16 6002000Calcite CaCO30.25 50 0002000 1.65, 1.5 0.589CReacts with acidsSapphire Al2O3;5.5 ;1818 0.25.5 50 0001818 insoluble 1.77 0.55 Good strength, no cleavageALON 9AI2O3.5AIN 0.
38、25.5 50 0001700 1.8 0.6Spinel MgAI2O40.26 50 0001600 1.68 0.6Strontium Titanate SrTiO30.396 25 0001700 insoluble 2.4 HFBTitanium Dioxide TiO20.426 24 0001700 insoluble 2.62.9 H2SO4and AlkaliBLithium Fluoride LiF ;6.0 ;1667 0.27 50 0001429 slightly 1.39 1.39 AcidBZirconia ZrO20.367 27 0001500 insolua
39、ble 2.15 HF and H2SO4BSilicon Si 1.57 and10FIR66001430 insoluble 3.4 11.0 Reacts with HF, alkaliDYttria Y20.258 40 0001250 1.9 0.6Yttria (La-doped) 0.09La2O3-0.91Y2O30.258 40 0001250 1.8 0.6IRTRAN IEMgF228 5 0001 250 slightly 1.3 6.7 HNO3BMagnesium Oxide MgO 0.48 25 0001300 insoluble 1.6 5 Acid and
40、NH4saltsBFluorite CaF2;8.0 ;1250 0.210 50 0001000 insoluble 1.40 8.0 Amine salt and NH4saltsBStrontium Fluoride SrF20.1311 77 000909 slightly 1.4IRTRAN IIIECaF20.211 50 000909 insoluble 1.34 5.0 Polycrystalline, no cleavageGallium PhosphideGaPGaP 0.511 20 000910Lead Fluoride PbF20.312 3450833 1.7 1S
41、ervofraxFAs2S3112 10 000833 insolubleslightly (hot)2.59 0.67 AlkaliB, softens at 195CBarium Fluoride BaF2;11 ;909 0.213 50 000769 insoluble 1.45 5.1AMTIR GeAsSe Glass 0.914 11 000725 insoluble 2.5 10 Hard, brittle, attacked by alkali, goodATR materialIRTRAN IIEZnS 114 10 000714 insoluble 2.24 5.5 In
42、soluble in most solventsIndium Phosphide InP 114 10 000725Potassium Floride KF 0.1615 62 500666 soluble 1.3 0.3 Extremely deliquescent: notrecommended for routine useRock salt NaCl ;16 ;625 0.216 50 000625 soluble 1.52 4.7 Soluble in glycerineGCadmium Sulfide CdS 0.516 20 000625Arsenic Triselenide A
43、s2Se30.817 12 500600 slightly 2.8 Soluble in basesGallium Arsenide GaAs 117 10 000600 insoluble 3.14 Slightly soluable in acids and basesGermanium Ge 220 5 000500 insoluble 4.0 13.0Sylvite KCl 0.321 33 333476 soluble 1.49 0.5 Soluble in glycerineGIRTRAN IVEZnSe 121 10 000476 insoluble 2.5 1.0 Polycr
44、ystallineSodium Bromide NaBr 0.223 50 000435 soluble 1.7 0.35Sodium Iodide NaI 0.2525 40 000400 soluble 1.7 0.5Silver Chloride AgCl ;22 ;455 0.625 16 6667400 insoluble 2.0 3.8 Soft, darkens in lightHreacts withmetalsPotassium Bromide KBr ;25 ;400 0.227 50 000370 soluble 1.53 8.6 Soluble in alcohol;
45、fogsCadmium Telluride CdTe ;28 ;360 0.528 20 000360 insoluble 2.67 10 Acids, HNO3BThallium ChlorideTICI0.430 25 000330 slightly 2.2 0.75 ToxicKRS-6 Tl2CIBr 0.432 25 000310 slightly 2.02.3 0.624 ToxicSilver Bromide AgBr ;35 ;286 235 5 000286 insoluble Soft, darkens in lightH, reacts withmetalsKRS-5 T
46、l2Brl ;40 ;250 0.738 14 286263 slightly 2.38 4.0 Toxic, soft, soluble in alcohol, HNO3BCesium Bromide CsBr ;35 ;286 0.340 33 333250 soluble 1.66 8.0 Soft, fogs, soluble alcoholsPotassium Iodide Kl 0.1545 66 600220Thallium Bromide TIBr 0.4545 22 000220 slightly 2.3 0.625 ToxicCesium Iodide CsI ;52 ;1
47、92 0.350 33 330220 soluble 1.74 8.0Low-densitypolyethylene(CH2CH2)n 20220 50045 insoluble 1.52 Very soft, organic liquids penetrateinto polymer at ambienttemperatureType 61I(CH2CH2)n 2220 5 00045 insoluble 1.52 Softens at 90CType 62I(CF2CF2)nJ2220 5 00045 insoluble 1.52 Useful to 200C for short dura
48、tionsDiamondJ2-4 and 4500-2500 insoluble 2.4 10 K2Cr2O7 , H2SO4B6-300 and 1667-33ACutoff range is defined as the frequency range within which the transmittance ofa2cmthicksample is greater than 0.5. FT-IR spectrometers may be able to work outsidethis range.BReacts with.COrdinary and extraordinary ra
49、ys.DLong wavelength limit depends on purity.ETrademark of Eastman Kodak Co.FTrademark of Servo Corp of America.GWindow material will react with some inorganics (for example, SO2, HNO3, Pb(NO3)2).HThese materials should be stored in the dark when not being used, and should not be placed in contact with metal frames.ITrademark of 3M.JMicroporous polytetrafluoroethylene.E1252 98 (2013)13Solutions are prepared, usually in the 5 to 10 % weight/volumera
