This document discusses dispersive transform infrared spectroscopy. It begins by providing an overview of infrared spectroscopy and how it can be used to identify chemical substances through absorption spectroscopy. It then describes the basic components of an infrared spectrometer, including how it produces an infrared spectrum by measuring absorbance or transmittance over a range of frequencies or wavelengths. The document goes on to explain Fourier transform infrared spectroscopy and how it records and processes interferograms into spectra. It also describes dispersive infrared spectroscopy and how it analyzes samples sequentially with single wavelengths using a monochromator. Finally, it outlines some common uses and applications of infrared spectroscopy in fields like quality control, forensics, and art analysis.

1. Dispersive Transform Infrared
Spectroscopy
Presented by: Arun Agarwal
(CSIR-JRF)
ID: 53253
Supervisor: Dr. Wahajuddin
(Principal scientist)
Division: Pharmaceutics and
pharmacokinetics

2. Infrared Spectroscopy
• Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy)
involves the interaction of infrared radiation with matter.
• It covers a range of techniques, mostly based on absorption
spectroscopy.
• As with all spectroscopic techniques, it can be used to identify and
study chemical substances.
• Samples may be solid, liquid, or gas.

3. Instrument
• Instrument called an infrared spectrometer (or spectrophotometer)
to produce an infrared spectrum.
• An IR spectrum can be visualized in a graph of infrared light
absorbance (or transmittance) on the vertical axis vs. frequency or
wavelength on the horizontal axis.
• Typical units of frequency used in IR spectra are reciprocal
centimeters (sometimes called wave numbers), with the symbol cm−1

4. Fourier transform infrared spectroscopy (FT-IR)
• It is a measurement technique that allows one to record infrared spectra.
Infrared light is guided through an interferometer and then through the
sample (or vice versa).
• A moving mirror inside the apparatus alters the distribution of infrared
light that passes through the interferometer.
• The signal directly recorded, called an "interferogram", represents light
output as a function of mirror position.
• A data-processing technique called Fourier transform turns this raw data
into the desired result (the sample's spectrum).

5. Dispersive Transform Infrared Spectroscopy
• An alternate method for acquiring spectra is the "dispersive" or
"scanning monochromator" method.
• In this approach, the sample is irradiated sequentially with various
single wavelengths.
• The dispersive method is more common in UV-Vis spectroscopy, but is
less practical in the infrared than the FTIR method.

6. Dispersive IR Spectrometer
• The general set up of a dispersive IR instrument is similar to that of the
double beam UV-visible instrument.
• However there are two differences.
• Firstly, the radiation emerging out of the sample cell is dispersed with the help of a
suitable grating and not by diffraction grating as in UV-VIS spectrometers.
• Secondly, in IR, the sample is located between the source and the monochromator.
• This arrangement helps in getting rid of the scattered radiation from the
cell compartment.

7. Working picture of Dispersive IR spectrometer

8. Uses and applications
• Infrared spectroscopy is a simple and reliable technique widely used in both
organic and inorganic chemistry, in research and industry.
• It is used in quality control, dynamic measurement, and monitoring applications
such as the long-term unattended measurement of CO2 concentrations in
greenhouses and growth chambers by infrared gas analyzers.
• It is also used in forensic analysis in both criminal and civil cases, for example in
identifying polymer degradation. It can be used in determining the blood alcohol
content of a suspected drunk driver.
• IR-spectroscopy has been successfully used in analysis and identification of
pigments in paintings. And other art objects.. Such as illuminated manuscripts

9. References
• https://en.wikipedia.org/wiki/Infrared_spectroscopy. (accessed on 9th
October 2019).
• https://shodhganga.inflibnet.ac.in/bitstream/10603/134021/9/09_ch
apter%203.pdf. (Accessed on 9th October 2019).

10. Thank you!!