APPLICATIONS OF INFRA RED SPECTROMETRY

IR spectroscopy is widely used in both research and industry as a simple and reliable technique for measurement, quality control and monitoring of dynamic processes. The intensity and position of the signals in infra-red spectrum allow the identification of structural elements like typical functional groups, hydrogen bonding, etc. It can also To minimise the strong background absorption help in the determination of conformations and even in monitoring the progress of chemical reactions. IR spectrometry finds applications in quite diverse areas like drugs and pharmaceuticals, chemical industry, polymer industry, forensic  determinations, air pollution monitoring, agriculture, semiconductor microelectronics, clinical and biomedical determinations etc. Let us discuss some of these applications. We would broadly put them into three categories viz. qualitative, quantitative and other applications.
Qualitative Applications

The most important qualitative application of the mid-IR spectrometry is in the
determination of the structures of organic and biochemical species. It is achieved in an
empirical method wherein the signals in the IR spectra are identified with the help of
correlation tables.
Structure Elucidation of Organic Molecules by IR Spectra
For structure determination of organic molecules, the infrared spectrum can be broadly
divided into two regions. The region spanning from 3600 to 1200 1 cm− is called the
functional group region and the region that includes all frequencies below 1200 cm-1
is called the fingerprint region. The two regions put together are important in the determination of the identity of a molecule. It is almost impossible to assign all the
possible frequencies observed in the IR spectrum. However, identification of the characteristic features in the functional group region that includes stretching vibrations, of typical functional groups found in organic molecules, is quite important
Checking the Authenticity of a Compound

A common application of IR spectra is the comparative analysis of the spectra of an unknown compound with the spectra of the likely compounds. For this purpose the IR spectra may be considered analogous to a fingerprint of an individual. Like, there are no two individuals with the same set of fingerprints there are no two molecules with identical IR spectra, more so in the fingerprint region. Now a days we can subscribe to voluminous sets of catalogues containing IR, UV, NMR and mass spectra which are updated periodically. To decipher the true identity of a molecule we need to run co-IR. Here, the IR traces of the test molecule and the corresponding authentic sample or its  spectrum from the available catalogues on the same chart are seen and matched. If the two compounds are identical then the signals in their IR spectra would match in terms of their positions and the relative intensities.
Monitoring the Progress of a Reaction

Another useful application of IR spectrometry is to monitor the progress of a reaction by monitoring the disappearance or appearance of a characterissignal. For example, the oxidation of a secondary alcohol to a ketone can be monitored in terms of the disappearance of the O-H signal in the IR spectrum of the reaction mixture or by the appearance of the carbonyl signal of the ketone being produced. The rate of such reactions can also be measured by taking the time dependant spectra and using the Beer-Lambert Law.tic IR absorption
Quantitative Applications

A number of simple, portable and yet dependable IR spectrometers are available that may be used to quantitatively analyse a mixture of gaseous pollutants in a short time.
These instruments are IR filter photometers and give good results
Clinical and Biomedical Applications

IR spectroscopy has been employed for the analysis of several analytes in different biofluids and solid biological samples. This has applications in the analysis of pathological samples, for diagnostic purposes and also for non-invasive in vivo monitoring. For example, mid-IR spectroscopy has been used for analysing the faecal fat content or for the determination of the composition of urinary and gall stones. IR spectroscopic methods have also been used for the simultaneous quantification of serum concentrations of total protein, albumin, triglycerides, cholesterol, glucose urea, creatinine and uric acid etc. The serum samples are spread as a thin film onto an IRtransparent material and measured in the mid IR region after drying of the serum film.Combinations of visible microscopy and IR spectroscopy (FT-IR-MC) have been used in the development of methods for the diagnosis and identification of cancer cells.