what is the purpose of: FT-IR and ATR-FT-IR Instrumentation: Until recently, most IR instruments were of a dispersive double-beam design. Now, most IR instruments are Fourier transform spectrometers. The FT-IR instrument allows all wavelength of IR radiation to fall on the sample at the same time. The interferometer utilizes positive and negative interference at a series of wavelengths as a function of changing path length of the IR beam to create the spectrum. While the initial output from the detector, known as an interferogram, does not look like an IR spectrum at first, mathematical transformation (Fourier transform) converts the absorption information from a time domain to a frequency domain - creating the traditional IR spectrum. Use of the FT-IR instrument provides a principal advantage in the speed of the analysis, with all wavelengths of interest being measured simultaneously in less than one second. As such, a large number of spectra can be gathered within a short period of time. While solids, liquids, and gasses can be analyzed by IR spectroscopy, sample preparation for the condensed phases poses a challenge. First, appropriate materials for sample compartments are required as both glass and plastic absorb within the IR region of the electromagnetic