FT-IR stands for Fourier Transform Infrared. "It is a technique based on the determination of the interaction between an IR radiation and a sample that can be solid, liquid or gaseous". It measures the frequencies at which the sample absorbs, and also the intensities of these absorptions. The frequencies are helpful for the identification of the sample's chemical make-up due to the fact that chemical functional groups are responsible for the absorption of radiation at different frequencies. The concentration of component can be determined based on the intensity of the absorption. The spectrum is a two-dimensional plot in which the axes are represented by intensity and frequency of sample absorption. 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). The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample. Like a fingerprint no two unique molecular structures produce the same infrared spectrum. This makes infrared spectroscopy useful for several types of analysis. The FTIR provides the information related to the i) identification of unknown materials ii) It can determine the quality or consistency of a sample iii) It can determine the amount of components in a mixture. Today FT-IR instruments are digitalized and are faster and more sensitive than the older ones. FT-IR spectrometers can detect over a hundred volatile organic compounds (VOC) emitted from industrial and biogenic sources. Gas concentrations in stratosphere and troposphere were determined using FT-IR spectrometers.

FTIR can be used in all applications where a dispersive spectrometer was used in the past. In addition, the multiplex and throughput advantages have opened up new areas of application these include as under:

1. Environmental Monitoring: FT-IR spectroscopy used in air pollutants detection and measuring is that every gas has its own „fingerprint" or absorption spectrum. The entire infrared spectrum will be monitored and FTIR sensor will read the different fingerprints of the gases present in the air sample. Volcanoes are considered important natural sources of air pollution. The most abundant gas typically released into the atmosphere by volcanoes is water vapour (H2O), followed by carbon dioxide (CO2) and sulfur dioxide (SO2). Other gases such as hydrogen sulphide (H2S), carbon monoxide (CO), hydrochloric acid (HCl), hydrofluoric acid (HF), hydrogen (H2), helium (He), silicon tetra fluoride (SiF4), carbon oxysulfide (COS) are released by volcanoes in small amounts. From the most dangerous to human, animals and agriculture are carbon dioxide, sulphur dioxide and hydrofluoric acid. Therefore it is important to monitor volcanic activities. A telescope-attached FT-IR spectral radiometer was used to study the volcanic gases in seven active volcanoes from Japan. The open-path FT-IR Spectroscopy is conventionally used for monitoring gaseous air pollutants, but can also be used for monitoring both the gaseous or particulate air pollutants.

2. Identification of bio aerosol: FT-IR spectroscopy has widely been used for the characterization and identification of bacteria and yeasts, due to the fact that they are hydrophilic microorganisms and can easily be suspended in water for sample preparation. The identification of airborne fungi using FT-IR spectroscopy was described by Fischer and co-workers. They found that the method was suited to reproducibly differentiate Aspergillus and Penicillium species. The results obtained can serve as a basis for the development of a database for species identification and strain characterization of micro fungi.

3. Monitoring heavy metal from wastewater: Studies on heavy metals and organic compounds removal from wastewaters using different natural and synthetic materials are many. The important role of FTIR spectroscopy in such studies is either related to the characterization of sorbents, chemical modified sorbents.

4. Bio sorbent: Pollutants FT-IR spectroscopy has been used to identify the nature of possible sorbent (biosorbent) - pollutants (heavy metals, inorganic compounds, organic compounds) interactions. For copper removal by fungal biomass to determine the characteristic functional groups that are responsible for biosorption of copper ions were made biomass's FTIR spectra before and after the biosorption process took place. The bonding mechanism between copper and biomass (fungal strain, cyanobacteria or other microorganism can be determined by interpreting the infrared absorption spectrum.

5. Biotransformation: In case of biological degradation of pollutants a significant role can be attributed to biodegradation pathway due to the fact that different biodegradation pathways lead to different biodegradation products. Thus it is important to determine biodegradation pathways. For this purpose FTIR spectroscopy is a relevant tool for rapid determination of the resulting biotransformation product or mixtures. The structural changing in biodegradation processes can be determined by FTIR analysis.

6. Monitoring stages of composting: FT-IR spectroscopy is a quick and useful method to monitor the composting process. FTIR spectroscopy gives information regarding the stage of organic matter for process and product control, and for process and product control, and for monitoring of landfill remediation monitoring of landfill remediation.it elucidate the typical IR absorption bands and correlation of band growth rates with the compost maturity or degradation degree.

7. Soil Characterization: Soil is a complex medium with important ecological functions. Its functions depend on its characteristics. FTIR spectroscopy can be used to describe soil characteristics in the form of complex multivariate data sets. Thus FTIR spectroscopy has been used to investigate soils at different stages of recovery from degradation following opencast mining and from undisturbed land. FT-IR spectrometer was used to determine gases from soils and rock formations no other gases than CO2 have been detected except CO. Monitoring of nitrate in soil is very important for managing fertilizer application and controlling nitrate leaching. This monitoring help to adjust nitrate level in soils in order to maintain the soil fertility, or to detect soil pollution.

8. Monitoring Bioremediation process: The biodegradation process can be monitored by FTIR spectroscopy. Bioremediation is defined as the elimination, attenuation or transformation of polluting or contaminating substances by the use of biological processes. After isolation of the bacterial strains, FTIR spectra helps to identify isolated bacterial strains have substantial potential to remediate the hydrocarbon contaminated soils.

9. Analysis of different processes: ATR-FTIR spectroscopy to be used for analysis of processes at surfaces, surface modification surface degradation, study of enzymatic degradation of a substrate film attached to a solid surface study of sunscreens on human skin research of cereal, food and wood systems detection of microbial metabolic products on carbonate mineral surfaces, self-assembled thin films, grafted polymer layers, adsorption processes of biological and synthetic materials.
10. Identification of radionuclides waste: ATR-FTIR and FT-IR spectroscopy together with other techniques were used to determine the fate and transport of radionuclides in natural environments.

Other Applications
I. Identification of polymers and polymer blends.
II. Indirect verification of trace organic contaminants on surfaces.
III. Routine qualitative & quantitative FTIR Analysis.
IV. Thin film analysis.
V. Analysis of adhesives, coatings and adhesion promoters or coupling agents.
VI. Small visible particle chemical analysis.
VII. Analysis of stains and surface blemishes remnant from cleaning and degreasing processes combined with optical microscopy.
VIII. Analysis of resins, composite materials and release films.
IX. Solvent extractions of leachable or contaminants, plasticisers, mould release agents and weak boundary layers coupled with XPS surface chemical analysis techniques.
X. Identification of rubbers and filled rubbers.
XI. Determination of degrees of crystallinity in polymers.
XII. Compararive chain lengths in organics.

About Author / Additional Info:
Myself Priti Pandita and I am a Research Scholar from central university of Gujarat.