Dispersive IR spectroscopy

In recent years, infrared spectroscopy has been enhanced by the possibility of applying Fourier transform techniques to it. This improved spectroscopic technique, known as Fourier transform infrared spectroscopy (FTIR), is of much greater sensitivity than conventional dispersive IR spectroscopy (Skoog West, 1980). Moreover, use of the Fourier transform technique enables spectra to be recorded extremely rapidly, with scan times of only 0-2 s. Thus it is possible to record spectra of AB cements as they set. By comparison, conventional dispersive IR spectroscopy requires long scan times for each spectrum, and hence is essentially restricted to examining fully-set cements. 

Despite the potential advantages of employing IR spectroscopy in fats and oils analysis, the only recognised application of IR spectroscopy in this area is the determination of isolated trails isomers in fats and oils by dispersive IR spectroscopy, which is an official method of the American Oil Chemists ... 

Infrared Spectroscopy Infrared spectroscopy has been one of the most frequently used instrumental analysis methods to characterize qualitatively the surface functionalities in coals [224,225], carbon blacks [226], charcoals [227], activated carbons [80,228-233], activated carbon fibers [234,235], and carbon films [236,237]. Fourier analysis (FTIR) provides an improvement over dispersive IR spectroscopy in signal-to-noise (S/N) ratio, energy throughout, accuracy of the frequency scale, and a capacity for versatile data manipulation. 

List the advantages of FTIR over dispersive IR spectroscopy. 

Selenate. Harrison and Berkheiser (20) examined selenate sorption onto freshly precipitated hydrous ferric oxide using dispersive IR spectroscopy on air dried samples. They concluded that selenate forms a bidentate bridging complex, replacing both protonated and unprotonated hydroxyls. 

Detectors for IR radiation fall into two classes thermal detectors and photon-sensitive detectors. Thermal detectors include thermocouples, bolometers, thermistors, and pyroelectric devices. Thermal detectors tend to be slower in response than photon-sensitive saniconduc-tors. The most common types of detectors used in dispersive IR spectroscopy were bolometers, thermocouples, and thermistors, but faster detectors are required for FTIR. FTIR relies on pyroelectric and photon-sensitive semiconducting detectors. Table 4.5 summarizes the wavenumber ranges covered by commonly used detectors. 

OIC Analytical Instruments produce the model 700 TOC analyser. This is applicable to solids. Persulfate oxidation at 90-100 °C followed by non-dispersive IR spectroscopy is the principle of this instrument. 

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