1. Infrared (IR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy provide information about the structure of molecules by analyzing the absorption of IR radiation and the resulting spectra. 2. IR spectrometers consist of a source of IR radiation, a sample holder, a detector, and a recorder. FTIR uses an interferometer which provides advantages over dispersive IR instruments. 3. Samples can be analyzed as solids, liquids, or gases using appropriate sample holders. Thermal detectors such as thermocouples and bolometers, and photon detectors are used to detect absorbed IR radiation.

1. 1
IR and FT-IR
Presented By,
Chetan M. Jain
First Year M.Pharm
(Quality Assurance)
Government College of Pharmacy,Amravati.
11/12/16

2. InFRaRed
SpecTRoScopy
 Intoroduction
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Provide useful information about structure of molecule.
Absorption of IR radiation by molecule and exhibit absorption
spectra.
Change in dipole moment.
Energy of radiation is directly proportional to wave number and
inversely proportional to wavelength.
Region Wavelength (µ) Wave number (cm-1
)
Near IR 0.75-2.5 1200-4000
Infrared 2.5-16 4000-625
Far IR 16-200 625-10 11/12/16
Chetan Jain

3. oRIgIn oF IR SpecTRa
 UV- Visible spectrum results in changes of electronic as
well as vibrational and rotational level in molecule.
 IR radiation shows only vibrational and rotational level.
 Vibrational-Rotational spectrum.
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4. 4
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5. InSTRumenTaTIon
The optical components of IR spectrophotometer are
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Light Source
Monochromator
Sample Holder
Detector
Recorder
11/12/16Chetan Jain
Dispersive instruments
FT-IR instrument
Non-dispersive instruments

6. IR RadIaTIon SouRce
 Hot bodies continuously emmitting radiation
 Incandescent lamp
 Nernst Glover
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A closed wound nichrome wire is used.
A black oxide film formed on the coil gives emissivity by heating.
Temp. can be raised to 1100°C.
Used in near IR region and failed in IR region.
In IR region – most common source.
Consists of hollow rod-2mm in dia and 2-5cm in length.
Composed of mixture of oxides like zirconium, yttrium and thorium.
Temp: 1000-1800°C.
11/12/16Chetan Jain

7.  Advantages of Nernst glower
 Disadvantage
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It emits IR radiation over wide range of wavelength.
The intensity of radiation maintains steady and constant over long period
of time.
Used in air as it is not oxidized.
Frequent mechanical failure.
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8.  Globar Source
 Mercury Arc
 Tungsten Filament lamp
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It is rod of sintered silicon carbide about 5cm in length and 4mm in
diameter
Temp- 1300°C.
 If radiation above 10µ it is used.
Far IR region it is used.
It is encolosed in quartz jacket to reduce loss.
Useful for near IR region only.
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9. MonochroMators
 Select desired frequencies and reject other frequencies.
 These are of two types
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1) Prism Monochromator
2) Grating Monochromator
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10. PrisM
MonochroMator
 Greater range and simplicity.
 Halogens salts are used.
 Crystalline NaCl: 5-15µ
 Crystalline KBr/CBr: 15-40 µ
 LiF : 0.75-2.5
 Two types
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Single beam monochromator
Double beam Monochromator
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11. GratinG MonochroMator
 Series of parallel straight lines cut into plane
surface.
 Constructed from glass coated with aluminium.
 Gives radiation into single order.
 Advantages
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Not attacked by moisture.
Used over considerable wavelength.
Sturdy and long lasting.
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12. saMPle holders and saMPlin
of substance
 Used for solid, liquid and gas.
 Material containing sample must be transperent to
IR region.
 Sample cell constructed from rock salt.
 Sample must be pure and free from water.
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13. saMPlinG of solids
 Solid dissolved in solvent
 As Solid Film
 Mull technique
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Carbon tetrachloride,Chloroform,acetone and cyclohexane.
Sample solution is placed on surface of KBr or Nacl and
allowed to evaporate.
Solid sample mixed with nujol to form a paste. This paste is
then sandwiched between two salt plates and used for spectral
measurement.
Nujol has absorption at 2915,1462,1376 and 719cm-1
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14.  Pressed Pellet Technique(Disk Method)
 Advatages of pellet tech. over mull tech. is
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The small amount of finally ground solid sample is mixed with
100 times its weight of powdered KBr.
This mixture is pressed under high pressure in IR tablet press
to form pellet.
Eliminates the problem of band
If KBr pellet is preserved can be reused
Resolution of KBr is superior
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15. saMPlinG of liquids
 For sampling of various cell like sandwitch cell,demountable cell
and cavity cell are used.
 Made up of Nacl, KBr or thallium bromide.
 Demountable cell:
 Cavity cell:
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It consists of pair of salt plates separeted by gasket made of
metal or teflon and together by an clamp.
Matching a parallel-sided hole in a salt block makes it.
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16. saMPlinG of Gas
 The dried gases introduced via a stop cock.
 The gas sample is introduced into the gas cell made up of
glass or metal cylinder of about 10cm long.
 The end walls of the gas cell made up of NaCl.
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17. Detectors
 Two types of detectors are used
 Thermal detectors
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Thermal detectors
Photodetectors
When IR radiation falls on these detectors they cause heating
which give rise to P.D. This P.D. is depends upon amt of
radiation. Thermocouple
Bolometer
Thermister
Golay cell 11/12/16Chetan Jain

18.  Thermocouple
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These are dissimilar strips of metal join together at one end.
Two fine wires of metals are welded with blackened gold foil,
which absorbs radiation.
One welded joint(Cold junction) is kept at constant temp.
The other welded joint (Hot junction) is exposed to radiation.
This exposure of hot junction causes rise in its temp, cause the
P.D. proportional to the amt of radiation.
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19.  Bolometers
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These are constructed from metals or semiconductors.
When IR radiation falls on bolometer its temp. changes cause
change in the resistence of the conductor.
This change in the resistence of conductor is depends upon amt
of radiation.
This made one arm of Wheistone Bridge.
If IR radiation falls on the bolometer, the bridge becomes
unbalanced due to change in the electrical resistence causes
current flow through galvanometer.this amt of current flow is a
measure of intensity of radiation.
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20.  Thermister
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These function similar to bolometer.
These are the resisters made by fusing several metallic
oxides.
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21.  Golay cell
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It consists of metal cylinder.
One end of which closed by balanced metal plate and other with
metalised diaphragm.
Cylinder is filled with gas like xenon.
When the radiation falls on blackened metal plate it is heated which
causes expansion of gas, which affect the motion of diaphragm.
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22. Photon Detectors
 Used in near IR region.
 Consists of semiconductors like lead sulphide, lead
telluride.
 When radiation are fall on these they goes to higher
level and produce signal.
 Photoconductivity cell
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It consists of thin layer of lead sulphide supported on glass
and enclosed into an evacuated glass envelope.
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23. Fourier transForm ir
sPectroscoPy (Ftir)
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24. Fourier Transform IR
Spectroscopy (FTIR)
 Advanced technique.
 Interferometer(Michelson Interferometer).
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25.  Advantages
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Fellgett Advantage
Jacquinot advantage
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26. InterpretatIon of Ir Spectr
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27. applIcatIonS of Ir and ft
Ir
 Qualitative application
 Quantitative application.
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28. References
 Pharamceutical analysis by A.V. Kasture, S.G. Wadodkar,K.R.
Mahadik, H.N. More, Volume II, Nirali Prakashan, Eleventh
edition (2004), p.no. 207-221.
 Fundamental of analytical chemistry by D.A.Skoog,
D.M.West,F.J.Holler,7th
edition p.no.592-597.
 Organic Spectroscopy by William Kemp, 3rd
edition, Palgrave
Publication, p.no19-56.
 Instrumental Methods of Analysis by H.A.Willard, L.L.Merritt,
J.A.Dean, F.A. Settle, 7th
edition, p.no. 288 to 320.
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