Infrared spectroscopy applications in science

1. APPLICATIONS OF INFRARED
SPECTROSCOPY
DONE BY:
SHRUTHI K (18308019)
SUBJECT: TECHNIQUES IN
MICROBIOLOGY

2. INFRARED SPECTROSCOPY
◦ Infrared radiation is -1014 to 1011 Hz on the electromagnetic
spectrum.
◦ The energy of infrared radiation corresponds to energy differences
between different vibrational modes in molecules. Diatomic
molecules do not exhibit infrared absorption.
◦ If right amount of frequency is absorbed, the molecule is excited and
releases IR photon to come back to ground state.
◦ In graph of infrared, light transmittance on the vertical axis vs.
frequency or wavelength on the horizontal axis.

3. APPLICATIONS- which and what ?
1. Identification of functional group and structure
elucidation
◦ Group frequency region - 4000-1500 cm-1
◦ Fingerprint region - 1500-400 cm-1
◦ Each atom of the molecule is connected by bond and
each bond requires different IR region so characteristic
peaks are observed. This region of IR spectrum is called
as finger print region of the molecule. It can be
determined by characteristic peaks.

4. ADAPTED FROM SIGMA ALDRICH

5. 2. Identification of exchangeable Hydrogen:
◦ Many bands change frequency when deuterium is substituted for
Hydrogen.
◦ In general functional group is responsible for a given band, thus by
observing the shift, the groups in which exchange has occurred is
identified.
◦ A delay in shift due to the exchange is detected.
◦ Also, the number of hydrogen bonds and the functional groups
engaged in hydrogen bonding .
◦ Apart from this, small molecules like riboflavin and adenine are
detected and A:U ratio can be detected in tRNA. It is also used in
Studying the progress of the reaction .

6. ADAPTED FROM PHYSICAL BIOCHEMISTRY – DAVID
FREIFELDER

7. 3. Identification of substances
◦ IR spectroscopy is used to establish whether a given sample of an
organic substance is identical with another or not.
◦ This is because large number of absorption bands is observed in the
IR spectra of organic molecules and the probability that any two
compounds will produce identical spectra is almost zero. So if two
compounds have identical IR spectra then both of them must be
samples of the same substances.

8. 4. To track organic nano particles across the universe:
◦ Scientists at NASA released information about a family of complex,
carbon-rich molecules that are abundant throughout the universe.
◦ Scientists believe more than 20 percent of the carbon in the universe
is tied up to polycyclic aromatic hydrocarbons, or simply PAHs.
◦ Using the Ames-developed PAH Infrared Spectroscopic Database,
scientists will now have access to data on hundreds more compounds
and several powerful new tools –including an advanced web app and
a dedicated astronomical software package – to map the distribution
of this life-essential element and track its role across the universe.

9. 5. Protein quantification and determination:
◦ Polypeptides and proteins contains strong absorption bands (peptide
bonds) -CONH grouping. Termed as amide bands.
◦ Nine amide bands observed - amide A, amide B and amides I-VII in
order of decreasing frequency.
◦ Displacement coordinates:
1. C = O stretching (in plane)
2. C-N stretching (in plane)
3. N-H stretching (in plane)
4. OCN bending (in plane)
5. CNH bending (in plane)
6. Three out-of-plane: C-N torsion, C = O and N-H out-of-plane
bending.

10. SOURCE: JENA LIBRARY OF MACROMOLECULES

11. APPLICATION- when and where?
IRS is a powerful spectroscopy technique and can utilized for both
quantitative and qualitative analysis.
It is an appealing technology for the food industry because it is
simple, rapid, non-destructive measurement of chemical and
physical components.
◦ FTIR-Fourier Transform Infrared Spectroscopy.
Main aim is to measure the amount of light absorbed by a sample at
each wavelength.
Can detect range of functional groups and is sensitive to change in
molecular structure.

12. APPLICATIONS OF FTIR IN FOOD
Infrared milk analyzer -To determine fat, protein, lactose content.
Measurement of degree of unsaturation of fats and oils.
Identification of flavor and aroma.
Used to analyse and evaluate essential components from cinnamon
barks.
For packaging film - To identify structural changes occurred due to
exfoliation.
Identification of wheat varieties and Edible oils - FTIR-spectra of
bacteria are specific to a given strain and show the spectral
characteristics of cell components.

13. Attenuated Total Reflectance-FTIR.
Applied for ,
1.Sugar Analysis- Based on bands in 1250-900cm region.
2.Fruit containing product - Spectra for detection of adulteration
in fruit jams and purees.
3.Sweet Condensed Milk(SCM) - spectra region above 1500 cm is
dominated by water.
4.Fats and Oils - detection based up on peak height of absorption band
of isolated trans bonds at 996cm.

16. APPLICATION IN FORENSICS
Most of the evidence left at crime scene consists of organic
compounds.
It does not alter the evidence since very small amount of energy
are applied.
Used to identify forged of altered documents by shining beam
IRS.
Fibers of various kinds are often identified by this methods.

17. APPLICATION IN HOMELAND SECURITY
Identification of materials used to make improvised explosives.
Some these materials are not popular explosives like
nitroglycerin. (impurities)
But are toxic industrial materials(TIMs) and toxic industrial
chemicals(TICs).
Department of homeland security uses IRS technology to search
TIMs and TICs.

18. OTHER APPLICATIONS
1.Quantification of clinical parameters in body fluids
2.Analysis of kidney stone, nails and facial fat
3.Prediction of Azodicarbonamide in wheat flour.
4.Quantifying the total phenolic content and total carotenoid content in
blackberries.
5.Diagnosis and monitoring of cancer and other diseases by analysing
body fluids.

19. REFERENCES
◦ Infrared spectroscopy in forensic: definition and uses, Cheyenne
O, California, United states
◦ www.pharmatutor.org
◦ www.tecrea.com
◦ Freifelder D, Physical Biochemistry: Applications to
Biochemistry and Molecular biology, 1983, W.H Freeman
Publications
◦ https://www.pharmatutor.org/pharma-analysis/
◦ http://jenalib.leibniz-fli.de/
◦ https://www.nasa.gov/