 FT-IR stands for Fourier Transform Infrared, the preferred method of infrared spectroscopy. In infrared spectroscopy, IR radiation is passed through a sample. Some of the infrared radiation is absorbed by the sample and some of it is passed through (transmitted). An FTIR spectrometer simultaneously collects spectral data in a wide spectral range.

FT-IR provide following information It can identify unknown materials It can determine the quality or consistency of a sample It can determine the amount of components in a mixture

The spectrometer described here is a modified Bomem MB-100 FTIR. The heart of the FTIR is a Michelson interferometer. The mirror moves at a fixed rate. Its position is determined accurately by counting the interference fringes of a collocated Helium-Neon laser. The Michelson interferometer splits a beam of radiation into two paths having different lengths, and then recombines them. A detector measures the intensity variations of the exit beam as a function of path difference. A monochromatic source would show a simple sine wave of intensity at the detector due to constructive and destructive interference as the path length changes.

Source: MS thesis submitted by Carl George Schmitt, UNR, 1998

Components of FT-IR: 1)Radiation source 2)Monochromator 3)Sample cell and sampling of substance 4)Detector

The normal instrumental process is as follows: 1.The Source: Infrared energy is emitted from a glowing black-body source. This beam passes through an aperture which controls the amount of energy presented to the sample (and, ultimately, to the detector). 2.The Interferometer: The beam enters the interferometer where the “spectral encoding” takes place. The resulting interferogram signal then exits the interferometer. 3.The Sample: The beam enters the sample compartment where it is transmitted through or reflected off of the surface of the sample, depending on the type of analysis being accomplished. This is where specific frequencies of energy, which are uniquely characteristic of the sample, are absorbed. 4.The Detector: The beam finally passes to the detector for final measurement. The detectors used are specially designed to measure the special interferogram signal.

1.Liquid Samples: Neat sample Diluted solution Liquid cell 2.Solid Samples: Neat sample Cast films Pressed films KBr pellets Mull 3.Gas Samples: Short path cell Long path cell

Pressed pellet techniques:- Potassium bromide (KBr) is probably the most widely used matrix material -before use dried for 2 hours at 105º. -Sample Times KBr (1;100) -mixture is transferred to a die that has a barrel diameter of 13 mm. - Press at least psi. - clear glassy disk about 1 mm thick obtained - ready for transmission Evacuable KBr Die Potassium bromide 13 mm die.

1 Blank KBr was prepared Sample Kbr was prepared 2 Balnk KBr was placed in sample holder and the background was scanned 3 Sample pellets were placed in sample holder and background was scanned 4 smoothning 5 Label the peaks 6 printing

 Identification of inorganic compounds and organic compounds  Identification of components of an unknown mixture  Analysis of solids, liquids, and gasses  In remote sensing  In measurement and analysis of Atmospheric Spectra - Solar irradiance at any point on earth - Longwave/terrestrial radiation spectra  Can also be used on satellites to probe the space

Speed: Because all of the frequencies are measured simultaneously, most measurements by FT-IR are made in a matter of seconds rather than several minutes. Sensitivity: Sensitivity is dramatically improved with FT-IR for many reasons. The detectors employed are much more sensitive, the optical throughput is much higher which results in much lower noise levels, and the fast scans enable the co addition of several scans in order to reduce the random measurement noise to any desired level (referred to as signal averaging ). Mechanical Simplicity: The moving mirror in the interferometer is the only continuously moving part in the instrument. Thus, there is very little possibility of mechanical breakdown.

Internally Calibrated: These instruments employ a HeNe laser as an internal wavelength calibration standard. These instruments are self-calibrating and never need to be calibrated by the user.