Fourier transform infrared (FTIR) spectrometry is a useful tool for identifying both organic and inorganic chemicals. It can be utilized to quantify some components of an unknown mixture and can be used to analyze liquids, solids, or gases. Data are collected and converted from an interference spectrum.
Spectroscopy seeks to identify chemical properties by viewing the spectrum of emissions from a sample. The wavelength of light absorbed is characteristic of the chemical bonds in the substance. By interpreting the infrared absorption spectrum, the chemical bonds in a molecule can be determined. The spectrum of an unknown can be identified by comparing it to a known reference compound.
In traditional FTIR, a continuum source of light is used to produce light over a broad range of infrared wavelengths. Light coming from this continuum source is split into two paths. Using a mirror, this light is reflected from two mirrors back onto the beam splitter, where it is recombined. One of these mirrors is fixed; the second is movable. If the distance from the beam splitter to the fixed mirror is not exactly the same as the distance from the beam splitter to the second mirror, then when the two beams are recombined, there will be a small difference in the phase of the light between these two paths. For different wavelengths of light, there will be constructive and destructive interference, depending on the relative distances of the two mirrors of the beam splitter. If the intensity of light is measured and plotted as a function of the position of the movable mirror, the resultant graph is the Fourier Transform of the intensity of light as a function of wavenumber. To use the FTIR, the light is directed onto the sample and the intensity is measured using an infrared detector. The intensity of light striking the detector is measured as a function of the mirror position and then Fourier transformed to produce a plot of intensity vs. wavenumber. The peaks in these graphs will indicate the presence of molecules, and allow the chemical composition to be determined.
The experiments done at the MFC lab utilize FTIR to determine the composition of the ash that collects on the probe. This analysis allows us to determine whether the ash contains corrosive or polluting elements that could harm the boiler or the environment. Depending on the results, the fuel blend can be altered to minimize these harmful effects.