Advantages And Disadvantages Of Fifir Spectrometers

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5.2 FTIR INSTRUMENT:
Fourier Transform Infrared Spectrometer are widely used in food analysis ,petrochemical engineering organic synthesis, polymer science, pharmaceutical industry . FTIR spectrometers can be hyphenated to chromatography, and the detection of unstable substances the mechanism of chemical reactions and can be investigated with such instruments.[27]
5.2.1 HISTORY:
The first one who found that a spectrum and its interferogram are related by a Fourier transform was Lord Rayleigh, in 1892. But the Fellget was the first one who has converted an interferogram to its spectrum. Fast Fourier transform method on which the modern FTIR spectrometer based was introduced to the world by Turkey and Cooley in 1965. It has wide application
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The signal-to-noise ratio of spectrum is higher than the previous generation infrared spectrometers.
2. The scan time of all frequencies is short (approximately 1 s). (4) The resolution is extremely high (0.1 ~ 0.005 cm-1)
3. The scan range is wide (1000 ~ 10 cm-1).
4. The resolution is extremely high (0.1 ~ 0.005 cm-1)
5. The interference from stray light is reduced
6. The accuracy of wavenumber is high. The error is in the range of ± 0.01 cm-1.[27]

5.2.5 THE COMPONENTS OF FTIR SPECTROMETERS
FTIR consist of a sample compartment source, and amplifier,detector, A/D convertor, inferometer, and a computer. The source generates radiation which passes the sample through the interferometer and then it reaches to the detector. In the next step the signal is amplified and converted to digital signal by using the amplifier and analog-to-digital converter. The signal is transferred to a computer in which Fourier transform is carried out. The block diagram of an FTIR spectrometer is given below:[27]

5.2.6 MICHELSON
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One of the mirror is a stationary mirror and other one is a movable mirror. The beam splitter is used to transmit half of the light and reflect half of the light. Subsequently, the transmitted light and the reflected light strike the stationary mirror and the movable mirror. When reflected back by the mirrors, two beams of light recombine with each other at the beam splitter.[27]
If the distances travelled by two beams are the same, it means that the distances between two mirrors and the beam splitter are the same and the situation is defined as zero path difference (ZPD). But imagine if the movable mirror moves away from the beam splitter, the light beam which strikes the movable mirror will travel a longer distance than the light beam which strikes the stationary mirror. The distance which the movable mirror is away from the ZPD is defined as the mirror displacement and is represented by ∆. It is obvious that the extra distance travelled by the light which strikes the movable mirror is 2∆. The extra distance is defined as the optical path difference (OPD) and is represented by delta. Therefore, δ =

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