Infrared spectrometry, analysis

T. Nakamura, T. Takeuchi, A. Terada, Y. Tando, and T. Suda, Near-Infrared Spectrometry Analysis of Fat, Neutral Sterols, Bile Acids, and Short-Chain Fatty Acids in the Feces of Patients with Pancreatic Maldigestion and Malabsorption, Int. J. Pancreatol., 23(2), 137-143 (1998). 

Data Analysis. The computerization of spectrometers and the concomitant digitization of spectra have caused an explosive increase in the use of advanced spectmm analysis techniques. Data analysis in infrared spectrometry is a very active research area and software producers are constantly releasing more sophisticated algorithms. Each instmment maker has adopted an independent format for spectmm files, which has created difficulties in transferring data. The Joint Committee on Atomic and Molecular Physical Data has developed a universal format for infrared spectmm files called JCAMP-DX (52). Most instmment makers incorporate in thek software a routine for translating thek spectmm files to JCAMP-DX format. 

The environmental appHcations of infrared spectrometry are many and varied. Many appHcations at industrial sites are analogous to those for on-line process analysis waste streams and recycling processes can be monitored in the same way. Commercial infrared stack-gas monitors are based on either an extractive probe attached to a long-path gas ceU or an open-path (across stack) configuration (69). Stack plume and flare monitoring can be done externally... 

A predictive macromolecular network decomposition model for coal conversion based on results of analytical measurements has been developed called the functional group, depolymerization, vaporization, cross-linking (EG-DVC) model (77). Data are obtained on weight loss on heating (thermogravimetry) and analysis of the evolved species by Eourier transform infrared spectrometry. Separate experimental data on solvent sweUing, solvent extraction, and Gieseler plastometry are also used in the model. 

Table 5.8 Polypeptides detected during the LC-electrospray-MS analysis of the tryptic digest from / -lactoglobulin (/ILG). Reprinted from 7. Chromatogr., A, 763, Tnrnla, V. E., Bishop, R. T., Ricker, R. D. and de Haseth, J. A., Complete structnre elncidation of a globular protein by particle beam hqnid chromatography-Fourier transform infrared spectrometry and electrospray hqnid chromatography-mass spectrometry - Seqnence and conformation of / -lactoglobulin , 91-103, Copyright (1997), with permission from Elsevier Science...

The Analysis of Extraterrestrial Materials. By Isidore Adler Chemometiics. By Muhammad A. Sharaf, Deborah L. Illman, and Bruce R. Kowalski Fourier Transform Infrared Spectrometry. By Peter R. Griffiths and James A. de Haseth Trace Analysis Spectroscopic Methods for Molecules. Edited by Gary Christian and James B. Callis... 

Quantitative Analysis. Sampling Procedures. Near Infrared Spectrometry. Applications of Infrared Spectrometry. 

Most cells used in infrared spectrometry have sodium chloride windows and the path length is likely to vary with use because of corrosion. For quantitative work, therefore, the same cell should be used for samples and standards. In general, quantitative analysis in the infrared region of the spectrum is not practised as widely as in the ultraviolet and visible regions, partly because of the additional care necessary to obtain reliable results and partly because the technique is generally considered to be less sensitive and less precise a precision of 3-8% can be expected. 

A feature of this analytical scheme is the marked reliance on infrared spectrometry and titrimetry. The former is particularly applicable to the qualitative characterization of unknown organic materials whilst titrimetry provides a rapid, precise and cheap means of quantitative analysis. The routine titrimetric determination of water, total acid (acid number) and total base (base number) forms a significant proportion of the work load in some analytical laboratories. It is instructive to consider how other techniques might have been applied to the solution of this particular problem, e.g. NMR spectrometry and chromatography. 

In order to perform qualitative and quantitative analysis of the column effluent, a detector is required. Since the column effluent is often very low mass (ng) and is moving at high velocity (50-100 cm/s for capillary columns), the detector must be highly sensitive and have a fast response time. In the development of GC, these requirements meant that detectors were custom-built they are not generally used in other analytical instruments, except for spectroscopic detectors such as mass and infrared spectrometry. The most common detectors are flame ionization, which is sensitive to carbon-containing compounds and thermal conductivity which is universal. Among spectroscopic detectors, mass spectrometry is by far the most common. 

Commonly used methods for the determination of petroleum hydrocarbon contamination in soil are modifications of Environmental Protection Agency method 418.1, which use sonication or a Soxhlet apparatus for analyte extraction and either infrared spectrometry [5] or gas chromatography with flame ionization detection [6-7] for extract analysis. Regardless of the analytical method following the extraction, both modifications use Freon-113, which has been implicated as a cause of ozone depletion. Therefore, alternative methods are being sought for the determination of hydrocarbon contamination in environmental samples that reduce the need for this halogenated solvent. 

The most straightforward method for analyzing a solid material by infrared spectrometry is to dissolve it in a suitable solvent and then to measure this solution using a liquid sampling cell such as one of the several described in Section 8.8. Thus it becomes a liquid sampling problem, the experimental details of which have already been discussed (Section 8.8). It is the only method of solid sampling suitable for quantitative analysis because it is the only one that has a defined and reproduced pathlength. 

Quantitative analysis procedures using infrared spectrometry utilize Beer s law. Thus only sampling cells with a constant pathlength can be used. Once the percent transmittance or absorbance measurements are made, the data reduction procedures are identical with those outlined in Chapter 7 (preparation of standard curve, etc.). 

We discussed the fundamentals of mass spectrometry in Chapter 10 and infrared spectrometry in Chapter 8. The quadrupole mass spectrometer and the Fourier transform infrared spectrometer have been adapted to and used with GC equipment as detectors with great success. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectrometry (GC-IR) are very powerful tools for qualitative analysis in GC because not only do they give retention time information, but, due to their inherent speed, they are also able to measure and record the mass spectrum or infrared (IR) spectrum of the individual sample components as they elute from the GC column. It is like taking a photograph of each component as it elutes. See Figure 12.14. Coupled with the computer banks of mass and IR spectra, a component s identity is an easy chore for such a detector. It seems the only real... 

There are many analytical techniques available that measure total petroleum hydrocarbon concentrations in the environment, but no single method is satisfactory for measurement of the entire range of petroleum-derived hydrocarbons. In addition, and because the techniques vary in the manner in which hydrocarbons are extracted and detected, each method may be applicable to the measurement of different subsets of the petroleum-derived hydrocarbons present in a sample. The four most commonly used total petroleum hydrocarbon analytical methods include (1) gas chromatography (GC), (2) infrared spectrometry (IR), (3) gravimetric analysis, and (4) immunoassay (Table 7.1) (Miller, 2000, and references cited therein). 

M. Blanco, D. Valdes, M.S. Bayod, F. Femandez-Mari and 1. Llorente, Characterization and analysis of polymorphs by near-infrared spectrometry. Anal. Chim. Acta, 502, 221-227 (2004). 

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