This document summarizes instrumentation used in infrared (IR) spectroscopy. It discusses various components used including dispersive and Fourier transform IR spectrometers. It also describes sources of radiation such as the Nernst glow, globular source, and incandescent wire source. Various sampling techniques for solids, liquids, and gases are mentioned. Detectors discussed include bolometers, thermocouples, thermistors, and Golay cells. The document provides references for further information.

1. INSTRUMENTATION OF IR SPECTROSCOPY
Presented by
Randeep Patro
M.Pharm(Pharmacology)
SCHOOL OF PHARMACEUTICAL SCIENCES
SIKSHA ‘O’ ANUSANDHAN (DEEMED TO BE UNIVERSITY) , BHUBANESWAR

2. a)Dipersive [ 1]
• Many moving parts causing
mechanical slippage.
• Stray light causes superior
reading.
• Slow scan speed
• Only narrow frequency of
radiation falls at a time.
• Sample is subjected to thermal
effect
b)Nondispersive [ 3]
• Used in the sample containging
carbon monoxide like gases.
• Very rarely used now a days
• Chopper providing low response
to noise ratio .

3. c) FTIR [4]
He-Ne laser is used to control the
velocity of the moving mirror.
Advantages
• stray light does not affect the detector
• A much larger beam used at all the times:
data collectio is easier.
• Rapid scan enables to monitor undergoing
changes in the sample
• Emission of IR by the sample will not
be detected.
• Only the mirror moves during an exp.
• Sample is not subjected for thermal
effect .

5. SOURCE OF RADIATION
It must have the fallowing ideal properties
• Intense enough for detection
• Steady source
• Extended over the desired wavelengths
a) Nernst Glower[2]
Diameter 1-3mm and length 2-5cm
Temp of 1000 to 1800◦ C
Emits max. radiation of 7100 cm-1
Disadvantage :
• The intensity of radiation remains steady and const over longer period of time
• It emits IR over wide wavelength range
• It has frequent mechanical failure
• Its energy is concentrated in the visible and near IR region of spectrum

6. b) Globular Source[2]
Diameter 5mm and length 5cm
Heated upto 1300 to 1700◦ C
Emits max. radiation of 5200 cm-1
Advantage :
• It is self starting
• Its temp coefficient is positive .it can be controlled with a variable
transformer
• It works at wavelengths longer than 0.15 µ
c) Incandescent Wire Source[3]
Lower intensity but longlife than nernst & Globular
Heated upto 1100k
No cooling require and maintenance free
Advantage :
• It fails in Far IR region because it is glass enclsoed and has a low
emission spectra

7. d) Mercury Arc Source[2]
In the far IR region (wave number <200 cm-1 )
it loses its effectiveness so a high pressure
mercury lamp are used
e) Tungsten Filament Lamp[3]
Convenient source for near IR region i.e 0.8-2.5µm
f) Nicrome Wire [2]
Heated Of surface temp 800-900◦C
Nicrome wire lamp Tungsten Filament Lamp

8. Monochromators
It achieve the desired frequency from radiation source
monochromators are used.
Two Types :
a) Prism [1]
Metal halide Prisms and NaCl Prisms are used
Two types :
single pass double pass

9. b) Grating[2]
240 lines per nm and
120 lines per nm
Sampling techniques :
1) Solid Sampling – solids run in solution, solid films, mull technique , pressed pallet
2) Liquid Sampling
3) Gas Samping – Gas absorption cells
Sample cell[3]

10. DETECTORS
a)Bolometer [1]
Response time = 4msec
Resistance increases = 0.4% per every ◦C
b)Thermocouples[1]
Response time = 60msec
To increase sensitivity Thermophyles
are used

11. c) Thermistors[1]
Fused mixture of metal oxides
Resistance changes = 5% per ◦C
d)Golay Cell[1]
Response time = 10-2 sec

12. e)Photocoductivity Cell[2]
Response time = 0.5msec
Limited to near IR region
f) Semiconductor Detector[2]
Insulator to Conductor time = 1msec
g)Pyroelectric Detector[2]
Electrostatic change with change in temp.of flake
Pyroelectric flake is cut from a single crystal
Ex ; Triglyceride sulphide

13. REFERENCES
1) Instrumental methods of chemical analysis , fifth revised and
enlarged edition by Gurdeep R. Chatwal, Sham K. Anand,
published by Himalaya Publishing House, Page no = 2.41-2.51
2) A text book of pharmaceutical analysis, Vol-2, by G.Vidya Sagar,
published by Kalyani Publishers, Page no = 313-325
3) Principles of instrumental analysis, Sixth edition, by Dougals A
Skoog, E James Holler, Stanley R. Crouch,published by Thomson
Higher Education, Page no = 438-452
4) Spectrometric identification of organic compounds, Seventh
Edition, by Robert M. Silverstein, Francis X. Webster, David J.
Kiemle, published by John Wiley and Sons ,Page no = 78-80