ASTM E1252-98(2021)
(Practice)Standard Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis
Standard Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis
SIGNIFICANCE AND USE
4.1 Infrared spectroscopy is the most widely used technique for identifying organic and inorganic materials. This practice describes methods for the proper application of infrared spectroscopy.
SCOPE
1.1 This practice covers the spectral range from 4000 cm−1 to 50 cm−1 and includes techniques that are useful for qualitative analysis of liquid-, solid-, and vapor-phase samples by infrared spectrometric techniques for which the amount of sample available for analysis is not a limiting factor. These techniques are often also useful for recording spectra at frequencies higher than 4000 cm–1, in the near-infrared region.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautions are given in 6.5.1.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1252 − 98 (Reapproved 2021)
Standard Practice for
General Techniques for Obtaining Infrared Spectra for
Qualitative Analysis
This standard is issued under the fixed designation E1252; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E932PracticeforDescribingandMeasuringPerformanceof
−1 Dispersive Infrared Spectrometers
1.1 This practice covers the spectral range from 4000cm
−1 E1421Practice for Describing and Measuring Performance
to 50 cm and includes techniques that are useful for quali-
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
tative analysis of liquid-, solid-, and vapor-phase samples by
eters: Level Zero and Level One Tests
infrared spectrometric techniques for which the amount of
E1642Practice for General Techniques of Gas Chromatog-
sample available for analysis is not a limiting factor. These
raphy Infrared (GC/IR) Analysis
techniques are often also useful for recording spectra at
–1
frequencieshigherthan4000cm ,inthenear-infraredregion.
3. Terminology
1.2 The values stated in SI units are to be regarded as
3.1 Definitions—Fordefinitionsoftermsandsymbols,refer
standard. No other units of measurement are included in this
to Terminology E131.
standard.
4. Significance and Use
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.1 Infraredspectroscopyisthemostwidelyusedtechnique
responsibility of the user of this standard to establish appro-
for identifying organic and inorganic materials. This practice
priate safety, health, and environmental practices and deter-
describes methods for the proper application of infrared
mine the applicability of regulatory limitations prior to use.
spectroscopy.
Specific precautions are given in 6.5.1.
1.4 This international standard was developed in accor- 5. General
dance with internationally recognized principles on standard-
5.1 Infrared (IR) qualitative analysis is carried out by
ization established in the Decision on Principles for the 3
functional group identification (1-3) or by the comparison of
Development of International Standards, Guides and Recom-
IR absorption spectra of unknown materials with those of
mendations issued by the World Trade Organization Technical
known reference materials, or both.These spectra are obtained
Barriers to Trade (TBT) Committee.
(4-8) through transmission, reflection, and other techniques,
such as photoacoustic spectroscopy (PAS). Spectra that are to
2. Referenced Documents
be compared should be obtained by the same technique and
2.1 ASTM Standards:
under the same conditions. Users of published reference
E131Terminology Relating to Molecular Spectroscopy
spectra (9-16) should be aware that not all of these spectra are
E168Practices for General Techniques of Infrared Quanti-
fully validated.
tative Analysis
5.1.1 Instrumentation and accessories for infrared qualita-
E334Practice for General Techniques of Infrared Micro-
tive analysis are commercially available. The manufacturer’s
analysis
manual should be followed to ensure optimum performance
E573Practices for Internal Reflection Spectroscopy
and safety.
5.2 Transmission spectra are obtained by placing a thin
uniform layer of the sample perpendicular to the infrared
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom- radiation path (see 9.5.1 for exception in order to eliminate
mittee E13.03 on Infrared and Near Infrared Spectroscopy.
interference fringes for thin films). The sample thickness must
Current edition approved April 1, 2021. Published April 2021. Originally
be adequate to cause a decrease in the radiant power reaching
ɛ1
approved in 1988. Last previous edition approved in 2013 as E1252–98(2013) .
the detector at the absorption frequencies used in the analysis.
DOI: 10.1520/E1252-98R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1252 − 98 (2021)
For best results, the absorbance of the strongest bands should materialsandpathlengths.Typicalpathlengthsare0.01mmto
be in the range from 1 to 2, and several bands should have 0.2mm.See5.2forconsiderationsinselectionofcellmaterials
absorbances of 0.6 units or more. There are exceptions to this and path lengths.
generalization based on the polarity of the molecules being
6.2 Capillary Films—Some liquids are too viscous to force
measured. For example, saturated hydrocarbons are nonpolar,
into or out of a sealed cell. Examination of viscous liquids is
and their identifying bands are not strong enough unless the
accomplished by placing one or more drops in the center of a
−1
C-Hstretchat2920cm isopaqueandthedeformationbands
flat window.Another flat window is then placed on top of the
are in the range from 1.5 to 2.0 absorbance units (A) at
liquid. Pressure is applied in order to form a bubble-free
−1 −1
1440cm to 1460cm . Spectra with different amounts of
capillary film covering an area large enough that the entire
sample in the radiation path may be required to permit reliable
radiation beam passes through the film. The film thickness is
analysis. If spectra are to be identified by computerized curve
regulated by the amount of pressure applied and the viscosity
matching, the absorbance of the strongest band should be less
of the liquid. A capillary film prepared in this manner has a
than 1; otherwise, the effect of the instrument line shape
path length of about 0.01 mm. Volatile and highly fluid
function will cause errors in the relative intensities of bands in
materials may be lost from films prepared in this manner.
spectra measured by dispersive spectrometers and by FT-IR
Demountable spacers can be used when a longer path length is
spectrometers with certain apodization functions (specially
required to obtain a useful spectrum.
triangular).
6.3 Internal Reflection Spectroscopy (IRS)—Viscous mate-
5.2.1 Techniques for obtaining transmission spectra vary
rials can be smeared on one or both sides of an internal
with the sample state. Most samples, except free-standing thin
reflection element (IRE). See Practices E573 for detailed
films, require IR transparent windows or matrices containing
information on this technique.
the sample. Table 1 gives the properties of IR window
materials commonly employed. Selection of the window ma- 6.4 Disposable IR Cards —These can be used to obtain
terial depends on the region of the IR spectrum to be used for spectra of non-volatile liquids.Avery small drop, usually less
analysis, on the absence of interference with the sample, and than 10 µLof the liquid, is applied near the edge of the sample
adequate durability for the sample type. application area. If the sample does not easily flow across the
substrate surface, it may be spread using an appropriate tool.
5.3 Spectraobtainedbyreflectionconfigurationscommonly
The sample needs to be applied in a thin layer, completely
exhibit both reflection and absorption characteristics and are
covering an area large enough that the entire radiation beam
affected by the refractive indices of the media and the inter-
passes through the sample. Note that any volatile components
faces.Spectralinterpretationshouldbebasedonreferencesrun
of a mixture will be lost in this process, which may make the
underthesameexperimentalconditions.Inparticular,itshould
use of a disposable card a poor choice for such systems.
be realized that the spectrum of the surface of a sample
recordedbyreflectionwilloftendifferfromthespectrumofthe 6.5 Solution Techniques:
6.5.1 Analysis of Materials Soluble in Infrared (IR) Trans-
bulkmaterialasrecordedbytransmissionspectroscopy.Thisis
parent Solvent: The Split Solvent Technique—Many solid and
because the chemistry of the surface often differs from that of
liquid samples are soluble in solvents that are transparent in
the bulk, due to factors such as surface oxidation, migration of
parts of the infrared spectral region. A list of solvents com-
species from the bulk to the surface, and possible surface
monly used in obtaining solution spectra is given in Table 2.
contaminants. Some surface measurements are extremely sen-
The selection of solvents depends on several factors. The
sitive to small amounts of materials present on a surface,
sample under examination must have adequate solubility, it
whereas transmission spectroscopy is relatively insensitive to
must not react with the solvent, and the solvent must have
these minor components.
appropriate transmission regions that enable a useful spectrum
5.3.1 Reflection spectra are obtained in four configurations:
to be obtained. Combinations of solvents and window materi-
5.3.1.1 Specular reflectance (7.5),
als can often be selected that will allow a set of qualitative
5.3.1.2 Diffuse reflectance (7.6),
solution-phasespectratobeobtainedovertheentireIRregion.
5.3.1.3 Reflection-absorption (7.7),
One example of this “split solvent” technique utilizes carbon
5.3.1.4 Internal reflection (7.9). Refer to Practices E573.
tetrachloride (CCl ) and carbon disulfide (CS ) as solvents.
4 2
This technique is also called Attenuated Total Reflection
(Warning—Both CCl and CS are toxic; keep in a well
4 2
(ATR), and
ventilated hood. Use of these solvents is prohibited in many
5.3.1.5 Grazing angle reflectance.
laboratories. In addition, CS is extremely flammable; keep
5.4 Photoacoustic IR spectra (11.2).
away from ignition sources, even a steam bath. Moreover, CS
is reactive (sometimes violently) with primary and secondary
5.5 Emission spectroscopy (11.4).
aliphatic amines and must not be used as a solvent for these
TEST METHODS AND TECHNIQUES
compounds. Similarly, CCl reacts with aluminum metal.
Dependingonconditionssuchastemperatureandparticlesize,
the reaction has been lethally violent.)
6. Analysis of Liquids
6.1 Fixed Cells—A wide range of liquid samples of low to
moderate viscosity may be introduced into a sealed fixed-path
The 3M disposable IR Card is manufactured by 3M Co., Disposable Products
length cell. These are commercially available in a variety of Division.
E1252 − 98 (2021)
TABLE 1 Properties of Window Materials (in order of long-wavelength limit)
A
Cutoff Range Useful Transmission Range
Chemical Water Refractive at
Window Material Remarks
−1 −1
Composition Solubility Index (;µm)
(µm) (cm ) (µm) (cm )
B
Glass SiO + ;2.5 ;4000 0.35–2 28 570–5000 insoluble 1.5–1.9 HF, alkali
B
Quartz (fused) SiO ;3.5 ;2857 0.2–4 50 000–2500 insoluble 1.43 4.5 HF
SIlicon Nitrate Si N 0.3–4.5 33 000–2200
3 4
Silicon Carbide SiC 0.6–5 16 600–2000
C
Calcite CaCO 0.2–5 50 000–2000 1.65, 1.5 0.589 Reacts with acids
Sapphire Al O ;5.5 ;1818 0.2–5.5 50 000–1818 insoluble 1.77 0.55 Good strength, no cleavage
2 3
ALON 9AI O .5AIN 0.2–5.5 50 000–1700 1.8 0.6
2 3
Spinel MgAI O 0.2–6 50 000–1600 1.68 0.6
2 4
B
Strontium Titanate SrTiO 0.39–6 25 000–1700 insoluble 2.4 HF
B
Titanium Dioxide TiO 0.42–6 24 000–1700 insoluble 2.6–2.9 H SO and Alkali
2 2 4
B
Lithium Fluoride LiF ;6.0 ;1667 0.2–7 50 000–1429 slightly 1.39 1.39 Acid
B
Zirconia ZrO 0.36–7 27 000–1500 insoluable 2.15 HF and H SO
2 2 4
D
Silicon Si 1.5–7 and 6600–1430 insoluble 3.4 11.0 Reacts with HF, alkali
10–FIR
Yttria Y 0.25–8 40 000–1250 1.9 0.6
Yttria (La-doped) 0.09La O - 0.25–8 40 000–1250 1.8 0.6
2 3
0.91Y O
2 3
E B
IRTRAN I MgF 2–8 5000–1250 slightly 1.3 6.7 HNO
2 3
B
Magnesium Oxide MgO 0.4–8 25 000–1300 insoluble 1.6 5 Acid and NH salts
B
Fluorite CaF ;8.0 ;1250 0.2–10 50 000–1000 insoluble 1.40 8.0 Amine salt and NH salts
2 4
Strontium Fluoride SrF 0.13–11 77 000–909 slightly 1.4
E
IRTRAN III CaF 0.2–11 50 000–909 insoluble 1.34 5.0 Polycrystalline, no cleavage
Gallium Phosphide GaP 0.5–11 20 000–910
GaP
Lead Fluoride PbF 0.3–12 3450–833 1.7 1
F B
Servofrax As S 1–12 10 000–833 insoluble 2.59 0.67 Alkali, softens at 195 °C
2 3
slightly (hot)
Barium Fluoride BaF ;11 ;909 0.2–13 50 000–769 insoluble 1.45 5.1
AMTIR GeAsSe Glass 0.9–14 11 000–725 insoluble 2.5 10 Hard, brittle, attacked by alkali, good
ATR material
E
IRTRAN II ZnS 1–14 10 000–714 insoluble 2.24 5.5 Insoluble in most solvents
Indium Phosphide InP 1–14 10 000–725
Potassium Floride KF 0.16–15 62 500–666 soluble 1.3 0.3 Extremely deliquescent: not
recommended for routine use
G
Rock salt NaCl ;16 ;625 0.2–16 50 000–625 soluble 1.52 4.7 Soluble in glycerine
Cadmium Sulfide CdS 0.5–16 20 000–625
Arsenic Triselenide As Se 0.8–17 12 500–600 slightly 2.8 Soluble in bases
2 3
Gallium Arsenide GaAs 1–17 10 000–600 insoluble 3.14 Slightly soluable in acids and bases
Germanium Ge 2–20 5000–500 insoluble 4.0 13.0
G
Sylvite KCl 0.3–21 33 333–476 soluble 1.49 0.5 Soluble in glycerine
E
IRTRAN IV ZnSe 1–21 10 000–476 insoluble 2.5 1.0 Polycrystalline
Sodium Bromide NaBr 0.2–23 50 000–435 soluble 1.7 0.35
Sodium Iodide NaI 0.25–25 40 000–400 soluble 1.7 0.5
H
Silver Chloride AgCl ;22 ;455 0.6–25 16 6667–400 insoluble 2.0 3.8 Soft, darkens in light reacts with
metals
Potassium Bromide KBr ;25 ;400 0.2–27 50 000–370 soluble 1.53 8.6 Soluble in alcohol; fogs
B
Cadmium Telluride CdTe ;28 ;360 0.5–28 20 000–360 insoluble 2.67 10 Acids, HNO
Thallium Chloride 0.4–30 25 000–330 slightly 2.2 0.75 Toxic
TICI
KRS-6 Tl CIBr 0.4–32 25 000–310 slightly 2.0–2.3 0.6–24 Toxic
H
Silver Bromide AgBr ;35 ;286 2–35 5000–286 insoluble Soft, darkens in light, reacts with
metals
B
KRS-5 Tl2Brl ;40 ;250 0.7–38 14 286–263 slightly 2.38 4.0 Toxic, soft, soluble in alcohol, HNO
Cesium Bromide CsBr ;35 ;286 0.3–40 33 333–250 soluble 1.66 8.0 Soft, fogs, soluble alcohols
Potassium Iodide Kl 0.15–45 66 600–220
Thallium Bromide TIBr 0.45–45 22 000–220 slightly 2.3 0.6–25 Toxic
Cesium Iodide CsI ;52 ;192 0.3–50 33 330–220 soluble 1.74 8.0
Low-density (CH CH )n 20–220 500–45 insoluble 1.52 Very soft, organic liquids penetrate
2 2
polyethylene into polymer at ambient
temperature
I
Type 61 (CH CH )n 2–220 5000–45 insoluble 1.52 Softens at 90 °C
2 2
I J
Type 62 (C
...
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