1、Designation: E 1252 98 (Reapproved 2002)Standard Practice forGeneral Techniques for Obtaining Infrared Spectra forQualitative Analysis1This standard is issued under the fixed designation E 1252; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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 covers the spectral range from 400050cm1and includes techniques that are useful
3、 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
4、 region.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 limitations prior to use. Specif
5、ic precau-tions are given in 6.5.1.2. Referenced Documents2.1 ASTM Standards:E 131 Terminology Relating to Molecular Spectroscopy2E 168 Practices for General Techniques of Infrared Quanti-tative Analysis2E 334 Practices for General Techniques of Infrared Mi-croanalysis2E 573 Practices for Internal R
6、eflection Spectroscopy2E 932 Practice for Describing and Measuring Performanceof Dispersive Infrared Spectrometers2E 1421 Practice for Describing and Measuring Performanceof Fourier Transform Infrared (FT-IR) Spectrometers:Level Zero and Level One2E 1642 Practice for General Techniques of Gas Chroma
7、tog-raphy Infrared (GC/IR) Analysis23. Terminology3.1 DefinitionsFor definitions of terms and symbols, referto Terminology E 131.4. Significance and Use4.1 Infrared spectroscopy is the most widely used techniquefor identifying organic and inorganic materials. This practicedescribes methods for the p
8、roper 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
9、 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.
10、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 infraredradi
11、ation 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
12、 shouldbe in the range from 1 to 2, and several bands should haveabsorbances 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 unles
13、s 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 in theradiation path may be required to permit reliable analysis. Ifspectra are to be identified by computerized curve mat
14、ching,1This practice is under the jurisdiction of ASTM Committee E-13 on MolecularSpectroscopy and is the direct responsibility of Subcommittee E13.03 on InfraredSpectroscopy.Current edition approved March 10, 1998. Published June 1998. Originallypublished as E 1252 88. Last previous edition E 1252
15、94e1.2Annual Book of ASTM Standards, Vol 03.06.3The boldface numbers in parentheses refer to a list of references at the end ofthe text.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the absorbance of the strongest band should be le
16、ss than 1;otherwise, the effect of the instrument line shape function willcause errors in the relative intensities of bands in spectrameasured by dispersive spectrometers and by FT-IR spectrom-eters with certain apodization functions (specially triangular).5.2.1 Techniques for obtaining transmission
17、 spectra varywith the sample state. Most samples, except free-standing thinfilms, require IR transparent windows or matrices 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 us
18、ed foranalysis, on the absence of interference with the sample, andadequate durability for the sample type.5.3 Spectra obtained by reflection configurations commonlyexhibit both reflection and absorption characteristics and areaffected by the refractive indices of the media and the inter-faces. Spec
19、tral interpretation should be based on references rununder the same experimental conditions. In particular, it shouldbe realized 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 i
20、sbecause the chemistry of the surface often differs from that ofthe bulk, due to factors such as surface oxidation, migration 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 surfac
21、e,whereas transmission spectroscopy is relatively insensitive tothese minor components.5.3.1 Reflection spectra are obtained 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 Pra
22、ctices E 573.This technique is also called Attenuated Total Reflection(ATR), and5.3.1.5 Grazing angle reflectance.5.4 Photoacoustic 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 visc
23、osity may be introduced into a sealed fixed-pathlength cell. These are commercially available in a variety ofmaterials and 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 t
24、o forceinto or out of a sealed cell. Examination of viscous liquids isaccomplished by placing one or more drops in the center 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 t
25、he entireradiation beam passes through the film. The film thickness isregulated by the amount of pressure applied and the viscosityof 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 man
26、ner.Demountable spacers can be used when a longer path length isrequired to obtain a useful spectrum.6.3 Internal Reflection Spectroscopy (IRS)Viscous mate-rials can be smeared on one or both sides of an internalreflection element (IRE). See Practices E 573 for detailedinformation on this technique.
27、6.4 Disposable IR Cards4These can be used to obtainspectra of non-volatile liquids. A very small drop, usually lessthan 10 L 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 to
28、ol.The sample needs to be applied in a thin layer, completelycovering an area large enough that the entire radiation beampasses 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.
29、5 Solution Techniques:6.5.1 Analysis of Materials Soluble in Infrared (IR) Trans-parent Solvent: The Split Solvent TechniqueMany 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 spect
30、ra is given in Table 2.The selection of solvents depends on several factors. Thesample under examination must have adequate solubility, itmust not react with the solvent, and the solvent must haveappropriate transmission regions that enable a useful spectrumto be obtained. Combinations of solvents a
31、nd window materi-als can often be selected that will allow a set of qualitativesolution-phase spectra to be obtained over the entire IR region.One example of this “split solvent” technique utilizes carbontetrachloride (CCl4) and carbon disulfide (CS2) as solvents.NOTE 1Warning: Both CCl4and CS2are t
32、oxic; keep in a wellventilated hood. Use of these solvents is prohibited in many laboratories.In addition, CS2is extremely flammable; keep away from ignition sources,even a steam bath. Moreover, CS2is reactive (sometimes violently) withprimary and secondary aliphatic amines and must not be used as a
33、 solventfor these compounds. Similarly, CCl4reacts with aluminum metal.Depending on conditions such as temperature and particle size, thereaction has been lethally violent.6.5.1.1 Absorption by CCl4is negligible in the region4000-1330 cm1and by CS2in the region 1330-400 cm1incells of about 0.1 mm th
34、ickness. (Other solvents can be used.)Solutions are prepared, usually in the 510 % weight/volumerange, and are shaken to ensure uniformity. The solutions aretransferred by clean pipettes or by syringes that have beencleaned with solvent and dried to avoid cross-contaminationwith a previous sample. I
35、f the spectrum of a 10 % solutioncontains many bands that are too deep and broad for accuratefrequency measurement, thinner cells or a more dilute solutionmust be used.NOTE 2New syringes should be cleaned before use. Glass is thepreferred material. If plastic is used as containers, lids, syringes, p
36、ipettes,and so forth, analytical blanks are necessary as a check against contami-nation.4The 3M disposable IR Card is manufactured by 3M Co., Disposable ProductsDivision.E 1252 98 (2002)2TABLE 1 Properties of Window Materials (in order of long-wavelength limit)Window MaterialChemicalCompositionCutof
37、f RangeAUseful Transmission RangeWaterSolubilityRefractiveIndexat(;m)Remarks(m) (cm1) (m) (cm1)Glass SiO2+ ;2.5 ;4000 0.352 28 5705000 insoluble 1.51.9 HF, alkaliBQuartz (fused) SiO2;3.5 ;2857 0.24 50 0002500 insoluble 1.43 4.5 HFBSIlicon Nitrate Si3N40.34.5 33 0002200Silicon Carbide SiC 0.65 16 600
38、2000Calcite 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 0.25.5 50 0001700 1.8 0.6Spinel MgAI2O40.26 50 0001600 1.68 0.6Strontium Titanate SrTiO30.396 25 0001700 insoluble 2.4 HFBTitani
39、um 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 insoluable 2.15 HF and H2SO4BSilicon Si 1.57 and10FIR66001430 insoluble 3.4 11.0 Reacts with HF, alkaliDYttria Y20.258 40 0001250 1.9
40、 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 NH4saltsBFluorite CaF2;8.0 ;1250 0.210 50 0001000 insoluble 1.40 8.0 Amine salt and NH4saltsBStrontium Fluoride SrF20.1311 77
41、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 1ServofraxFAs2S3112 10 000833 insolubleslightly (hot)2.59 0.67 AlkaliB, softens at 195CBarium Fluoride BaF2;11 ;909 0.213 50 000
42、769 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 Insoluble in most solventsIndium Phosphide InP 114 10 000725Potassium Floride KF 0.1615 62 500666 soluble 1.3 0.3 Extremely deli
43、quescent: 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 As2Se30.817 12 500600 slightly 2.8 Soluble in basesGallium Arsenide GaAs 117 10 000600 insoluble 3.14 Slightly soluable in acid
44、s 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 PolycrystallineSodium Bromide NaBr 0.223 50 000435 Soluble 1.7 0.35Sodium Iodide NaI 0.2525 40 000400 Soluble 1.7 0.5Silver Chloride
45、 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; fogsCadmium Telluride CdTe ;28 ;360 0.528 20 000360 insoluble 2.67 10 Acids, HNO3BThallium ChlorideTICI0.430 25 000330 slightl
46、y 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 Tl2Brl ;40 ;250 0.738 14 286263 slightly 2.38 4.0 Toxic, soft, soluble in alcohol, HNO3BCesium Bromide CsBr ;35 ;286 0.340 33 3
47、33250 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 ;192 0.350 33 330220 soluble 1.74 8.0Low-densitypolyethylene(CH2CH2)n 20220 50045 insoluble 1.52 Very soft, organic liquids pene
48、trateinto 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 durationsDiamondJ2-4 and 4500-2500 insoluble 2.4 10 K2Cr2O7,H2SO4B6-300 and 1667-33ACutoff range is defined as the frequency range
49、 within which the transmittance ofa2cmthick sample is greater than 0.5. FT-IR spectrometers may be able to workoutside this range.BReacts with.COrdinary and extraordinary rays.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 pla
