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NIR (Near Infrared) and FT-IR (Fourier Transform Infrared) spectroscopy are the basis for an important new class of real-time process analyzers. Over the last 10 years, highly reliable process analyzer systems have evolved from the technology which has matured in laboratory uses since the late 1960's. Infrared spectrometers measure the spectrum of light (colors) which are absorbed, emitted or reflected from a material.
The most common use of full spectrum (multi-color) instrumentation has been in the refining and chemicals industries. In process analysis applications in these industries, samples are often liquid. A liquid sample to be measured is illuminated with a broad wavelength range of light (spectrum). The spectrometer measures the loss of light from the illuminating light at the point where the light exits the sample. Chemical compounds have unique absorption spectra -- the light loss is a unique fingerprint of the chemical compound. Mixtures of chemical compounds result in spectra which are the volume weighted sum of the individual compounds. Additional absorption features are often present in mixtures due to intermolecular interactions between the chemical compounds.
