Dispersive transform infrared spectroscopy

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!!