Dispersive infrared spectroscopy

OIC Analytical instruments produce the fully computerized model 700 total organic carbon analyser. This is applicable to soils and sediments. Persulphate oxidation at 90-100°C non-dispersive infrared spectroscopy is... 

Later chapters detail application of the present method to electron spectroscopy for chemical analysis (Chapter 5), high-resolution dispersive infrared spectroscopy (Chapter 6), and tunable-diode-laser spectroscopy (Chapter 7). Because the heart of the method is the repeated application of simple convolution, the method has been adapted to the processing of images (Kawata et al, 1978 Kawata and Ichioka, 1980a Saghri and Tescher, 1980 Maitre, 1981 Gindi, 1981). 

Deconvolution of spectra, such as infrared absorption spectra, provides researchers with a tool that they can use to carry out a particular experiment. It provides an extra measure of flexibility in the design of experiments and in the observation process. In dispersive infrared spectroscopic systems, Blass and Halsey (1981) have shown that effective resolution-acquisitiontime trade-offs may be made, owing to the fact that dispersive infrared spectroscopy is usually detector noise limited. Acquisition rates are therefore optical throughput dependent, which is equivalent to saying that acquisition rates are resolution dependent. Blass and Halsey (1981) show that, for a constant signal-to-noise ratio,... 

Dispersive Infrared Spectroscopy The dispersive IR spectrometer generally incorporates an IR broadband source, sample cell, a diffraction grating and one or more IR detectors. Dispersive IR instruments may provide simultaneous or sequential measurements. Respectively, the instrument may have a fixed grating and many detectors, or a movable grating and a single detector. In some cases, the grating may be replaced by one or more optical filters to resolve the desired wavelengths. A reference cell and associated optics to perform simultaneous differential analysis are also incorporated to improve sensitivity or reliability of measurement. 

It is likely that further applicationsi of sophisticated instrumentation to analysis of silicates will appear in future literature. In addition to ESCA, SIPS, X-ray spectroscopy, laser Raman and dispersive infrared spectroscopy, newer techniques such as Fourier transform infrared and photoacoustic spectroscopy may be used as tools to characterize silicate structure. 

Fourier Transform Infrared (FT-IR) Spectroscopy is one of the most versatile techniques available for providing analytical data on the raw materials, the process chemistry and the products. Dispersive infrared spectroscopy has traditionally been an important tool in fuel characterization since most organic and mineral components absorb in the IR. Discussions of applications to coal may be found in Lowry (1 ), van Krevlen (2 ), Friedel O), Brown (O, Brooks, Durie and Sternhell ( 5) Friedel and Retcofsky (O and references cited therein. But FT-IR with its advantages in speed, sensitivity and data processing has added new dimensions. 

FTIR takes a completely different approach. The spectral data are acquired as an Interferogram (Figure 1) which must be transformed Into a plot of Intensity versus wavenumber or wavelength through the application of Fourier transform equations. Thus, the computer Is an Integral part of the system without which little useful Information could be obtained. FTIR has the following advantages over computerized dispersive Infrared spectroscopy ... 

In addition to the abilities provided dispersive Infrared spectroscopy by Interfacing a computer, the FTIR adds the ability to select the resolution through software parameters. This sets the mirror displacement which, depending on the Instrument, can take on values from 0.125 cm l to 32 cmT. Good spectra are obtained with a resolution of 4 or 8 cm l. The farther the mirror travels, the greater the resolution but, at greater resolutions, the time for collection and computation of the spectral data Increases considerably. 

The classical dispersive infrared spectroscopy has been surpassed by Fourier-transform IR (FTIR), as the latter technique in general has a much higher speed, sensitivity and resolution [53,54]. As stated above, with respect to emulsion polymers the advantage of (FT)IR lies in the many polymer sample pes than can be analysed. Some typical PITR techniques are described below. 

At this point the FT-IR experiment may appear to be a rather difficult vdy to produce an infrared spectrum. Clearly, there must be some advantages to the technique to justify its existence. There are three distinct facets of FT-IR which make FT-IR superior to conventional dispersive infrared spectroscopy. 

There are various methods by which the impurities may be quantified, but dispersive infrared spectroscopy is often the method of choice.This method has serious shortcomings due to inherent problems with dispersive instruments such as poor resolution and poor wavenumber repeatability in the spectral regions of interest. A further criterion is that the wafer under test must be matched with a pure wafer of identical thickness. Only recently have FT-IR spectroscopic techniques been applied to the problem and considerable success has been realized. 

The extent of reaction ( is determined by mass balancing the open system in steady state. The concentrations of carbon monoxide and carbon dioxide are measured by non-dispersive infrared spectroscopy (Binos, Rosemount), oxygen is determined by use of a magnetic device (Magnos 3, Hartmann fz Braun). 

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

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