In this slide contains principle of IR spectroscopy and sampling techniques. Presented by: R.Banuteja (Department of pharmaceutical analysis). RIPER, anantpur.

1. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 1
Presented by
R. BHANUTEJA
(Reg. No: 20L81S0702)
Under the guidance of
Dr. P. Ramalingam, M. Pharm., PhD
Director – R&D Division &
Professor of Pharmaceutical Analysis and Medicinal Chemistry,
President – IPA Local Branch – Anantapuramu.
Sampling techniques in IR Spectroscopy
A seminar as a part of curricular requirement for 1st year
M. Pharm 1st semester

2. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 2
1. Basic principle of IR absorption
2. About IR Spectra
3. Sampling techniques in IR Spectroscopy
• Solid run in solutions
• Solid films
• Mull technique
• Sampling of liquids
• Sampling of Gas
4. References
Contents

3. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 3
• IR spectroscopy refers broadly to that region of electromagnetic spectrum
which lies between visible and microwave regions .
• This region is divided into different sections
Region Energy
(Kj/mol)
Wave number
(cm¯¹)
Wavelength
(µm )
Near IR 150-50 12,800-4000 0.78-2.5
Mid IR 50-2.5 4000-200 2.5-50
Far IR 2.5-0.1 200-10 50-1000
Basic principle of IR Absorption

4. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 4
In IR spectroscopy detects the absorption of light by a compound, in the
IR region of the electromagnetic spectrum .
To absorb light a molecule must have a bond within its structure that can
exhibit what is referred to as a dipole moment which means electrons
within a bond are not shared equally.
Applications
• Identification of functional groups and structural elucidation.
• Study of covalent bonds in molecule.
• Detection of impurities in a compound.
• Biomedical studies of human hair.

5. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 5
About IR Spectra
Graph plots:-
X-axis–wave number
Y-axis-transmittance

6. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 6

7. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 7
IR spectrum of ethanol

8. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 8
 Sampling in solids
Solid run in solution
Solid films
Mull technique
Pressed pellet technique
 Sampling in liquids
 Sampling in gases
Sampling techniques in IR spectroscopy

9. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 9
Solid is dissolved in non-aqueous inert solution
A drop of this solution is placed on alkali metal disc
Allow to evaporate & leaving a thin film of solute
Allow the thin film in spectrometer
Some solvents used are chloroform, carbon tetra chloride, Acetone,
cyclohexane etc.
SOLID RUN IN SOLUTIONS

10. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 10
If sample is polymer resins and amorphous solids
Dissolve the sample in a suitable (or) reasonable volatile solvent
Solution is mounted on rock salt plate (Nacl or KBR)
Evaporate by gentle heat
SOLID FILMS

11. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 11
• Small quantity of sample is thoroughly grind in a clean mortar until fine
powder.
• The mulling agent(mineral oil (or) nujol) is introduced in a small quantity
just sufficient to powder grind ,the powder & mulling agent approximately
the consistency of paste .
• Mixture transferred to mull plates and squeezed together to adjust the
thickness of sample between IR transmitting window.
• This is then mounted in path of ir beam and spectrum is run.
Although Nujol is transparent throughout IR region, it has absorption
maxima at 2915, 1462, 1376 & 719 cm−¹
Mull techniques

12. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
Mull technique

13. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 13
• A small amount of finely ground solid sample is mixed with 100 times its
weight of KBR in a vibrating ball mill.
• This finely ground mixture is then pressed under very high pressure (5000-
10000 psi) in a mini press to form a small pellet.
• The powder (sample + KBR) is introduced in between the 2 bolts and the upper
screw A is tightened until the powder is compressed to thin disc.
• After compressing the sample bolts A&A1 are removed and a steel cylinder
with pellet inside it is placed in path of the beam of IR spectrometer and
• A blank KBR pellet of identical thickness is kept in the path of reference beam.
Pressed pellet technique

14. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 14
Pressed pellet technique
Hydraulic press

15. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 15
Advantages
• The use of KBR eliminates the problem of bands which appear in IR
spectrum.
• Kbr pellets can be stored for long periods of time
• The resolution of spectrum in KBR is superior than any other
Disadvantages
• The high pressure involved during the formation of pellets may bring
polymorphic changes in crystalinity in sample .
• In some cases the substitution of ligand by bromide may be possible in
organic complexes
• The method not successful for some polymers which are difficult to grind with
kbr

16. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
• Liquid sample cells can be sandwiched using highly purified alkali halides such
as Nacl ,kbr ,caf2.
• The sample thickness should be selected so that the transmittance lies between
15-20%. For most of liquids the sample cell thickness is 0.01 -0.05 mm.
• Aqueous solvents cannot be used instead use organic solvents like chloroform,
Acetone, cyclohexane .
Sampling of liquids

17. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 17
• The IR radiation passes through a sample and chemical vapours in sample will
absorb the IR energy at different wave lengths.
• The gas cell is made up of Nacl and for low concentrated gases long path
length is required.
• Multi reflections can be used to make effective path length as long as 40 cm
so that constitutions of gas can be determined
• All compounds in the vapour will give unique fingerprints of absorbance
features which will compared to library of spectra.
Sampling of gases

18. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 18
1. Gurudeep.R.chatwal & sharm.K.Anand, Instrumental methods of chemical
analysis, 5th edition, pg.no.2.29.
2. Willard,merritt,dean&settle, Instrumental methods of analysis,7th
edition,pg.no.305-310.
3. B.K.Sharma, Insrumental methods of chemical analysis,26th
edition,pg.no.262-264.
4. https://www.pharmatutor.org
5. https://chem.libretexts.org
References

19. RIPER
AUTONOMOUS
NAAC &
NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
THANK YOU