The infrared region (10-14000 cm-1) of the electromagnetic spectrum is divided into three regions: the near-, mid-, and
far-IR. The mid-IR (400-4000 cm-1) is the most commonly used region for analysis as all molecules possess
characteristic absorbance frequencies and primary molecular vibrations in this range. Mid-infrared spectroscopy
methods are based on studying the interaction of infrared radiation with samples. As IR radiation is passed through a
sample, specific wavelengths are absorbed causing the chemical bonds in the material to undergo vibrations such as
stretching, contracting, and bending. Functional groups present in a molecule tend to absorb IR radiation in the same
wavenumber range regardless of other structures in the molecule, and spectral peaks are derived from the absorption of
bond vibrational energy changes in the IR region [20]. Thus there is a correlation between IR band positions and
chemical structures in the molecule. In addition to providing qualitative information about functional groups, IR spectra
can provide quantitative information, such as the concentration of bacteria in a growth medium.