Infrared spectra applications

P. Caceres-Alonso and A. Garcfa-Tejedor, Non-supervised neural categorisation of near infrared spectra. Application to pure compounds, J. Near Infrared Spectrosc., 3, 97-110 (1995). 

Gregg, C.J., et al., A variable-volume optical pressure-volume-temperature cell for high-pressure cloud points, densities, and infrared-spectra, applicable to supercritical-fluid solutions of polymers up to 2 Kbar. Journal of Chemical and Engineering Data, 1994. 39(2) p. 219-224. 

B. R. W. Hannah and S. C. Pattacini, The Identification of Drugs from Their Infrared Spectra, Applications Study 11, Perkin-Elmer Corp., Norwalk, CT, 1972. 

Tin oxide, Sn02, has unusual physical properties. It is a good electrical conductor. It is highly transparent to the visible and highly reflective to the infrared spectrum. It is deposited extensively by CVD mostly for optical applications. Its characteristics and properties are summarized in Table 11.6. 

The unique appearance of an infrared spectrum has resulted in the extensive use of infrared spectrometry to characterize such materials as natural products, polymers, detergents, lubricants, fats and resins. It is of particular value to the petroleum and polymer industries, to drug manufacturers and to producers of organic chemicals. Quantitative applications include the quality control of additives in fuel and lubricant blends and to assess the extent of chemical changes in various products due to ageing and use. Non-dispersive infrared analysers are used to monitor gas streams in industrial processes and atmospheric pollution. The instruments are generally portable and robust, consisting only of a radiation source, reference and sample cells and a detector filled with the gas which is to be monitored. 

The DIP concept is readily applicable to any part of the UV/visible/near infrared spectrum by the appropriate choice of the dye. Law, Vincett and Johnson (19), from these laboratories have reported the development of a infrared sensitive DIP disk. 

Absorbance subtraction can be considered as a spectroscopic separation technique for some problems in polymers. An interesting application in FT-IR difference spectroscopy is the spectral separation of a composite spectrum of a heterophase system. One such example is a semicrystalline polymer which may be viewed as a composite system containing an amorphous and crystalline phase53). In general, the infrared spectrum of each of these phases will be different because in the crystalline phase one particular rotational conformation will predominate whereas in the disordered amorphous regions a different rotamer will dominate. Since the infrared spectrum is sensitive to conformations of the backbone, the spectral contributions will be different if they can be isolated. The total absorbance A, at a frequency v of a semicrystalline polymer may be decomposed into the following contributions... 

This instrument has evolved from ihe laboratory spectrophotometer to satisfy the specific needs of industrial process control. While dispersive instruments continue to be used in some applications, the workhorse infrared analyzers in process control are predominantly nondispersive infrared (NDIR) analyzers. The NDIR analyzer ean be used for either gas or liquid analysis. For simplicity, the following discussion addresses the NDIR gas analyzer, hut it should be recognized that the same measurement principle applies to liquids. The use of infrared as a gas analysis technique is certainly aided by the fact that molecules, such as nitrogen (N ) and oxygen tO , which consist of two like elements, do not absorb in the infrared spectrum. Since nitrogen and oxygen are the primary constituents of air. it is frequently possible to use air as a zero gas. 

Most SHG studies involve incident energies in the visible or near-infrared spectrum. Infrared SHG studies are hindered by the current lack of sufficiently sensitive IR detectors. However, the sum frequency generation (SFG) technique allows one to obtain surface-specific vibrational spectra. In SFG, two lasers are focused on the sample surface, one with a fixed frequency in the visible and one with a tunable range of IR frequencies. The sample surface experiences the sum of these frequencies. When the frequency of the infrared component corresponds to a molecular vibrational mode, there is an increase in the total SHG signal, which is detected at the visible frequency [66]. The application of such... 

Another example is IR5 with a triplet state energy at 7700 cm-1 closely matching the acceptor 4Ii3/2 level of the Er111 ion at 6500 cm-1 (H.S. Wang et al., 2004). Moreover, excitation in the near-infrared spectrum is compatible with optical communication applications based on... 

The remainder of this paper will describe specific applications of FTIR in support of one of Diamond Shamrock s pesticide programs. All the results described here were obtained from studies of a single compound, thiofanox (P), 3,3-dimethy1-1-methylthio-2-butanone 0-[(methylamino)carbonyl]oxime. Thiofanox is a potent systemic and contact carbamate insecticide. The infrared spectrum of thiofanox is shown in Figure 4. The major peaks in the spectrum are the N-H stretch at 3380 cm-1,... 

Rigid Molecule Group theory will be given in the main part of this paper. For example, synunetry adapted potential energy function for internal molecular large amplitude motions will be deduced. Symmetry eigenvectors which factorize the Hamiltonian matrix in boxes will be derived. In the last section, applications to problems of physical interest will be forwarded. For example, conformational dependencies of molecular parameters as a function of temperature will be determined. Selection rules, as wdl as, torsional far infrared spectrum band structure calculations will be predicted. Finally, the torsional band structures of electronic spectra of flexible molecules will be presented. 

Figure 22 Vibrational spectra of human stratum comeum. FTIR Fourier transform infrared spectrum FT-Raman Fourier transform Raman spectrum. (From Ref. 185. Reprinted from International Journal of Pharmaceutics, 81 (2-3), Williams et al. Fourier transform Raman spectroscopy A novel application for examining human stratum comeum, pp. R11-R14,1992, with kind permission from Elsevier Science, ML, Sara Burgerhartstraaat 25, 1055 KV, Amsterdam, The Netherlands.)...

Infrared Spectroscopy, Application to Explosives Propellants. The infrared region is that portion of the electromagnetic spectrum which is located between visible light and the microwave radio re-... 

X-Ray analysis alone provides an absolute method for determining the molecular structure of a compound in the solid state. However, a consideration of the number of CO-stretching frequencies observed in the infrared spectrum of a carbonyl complex has proved invaluable in providing information about its structure both in the solid state and, more particularly, in solution. Applications of this latter approach to problems of molecular structure may now be discussed. As was noted in previous discussions, certain limitations must be considered in applying this method these will be taken into account. 

Figure 5. M.A.I.R. infrared spectrum of modified skin in situ (female forearm, underside, immediately after application of commercial moisture cream"" according to suppliers instructions)...

An interface between gel permeation chromatography (GPC) and Fourier transform infrared (FTIR) spectrometry has been developed. With this system it is possible to collect solvent free polymer deposition and to measure their infrared spectra as a function of molecular weight. The mobile phase from the GPC effluent is converted into an aerosol and removed using a pneumatic nozzle. The sample is collected on a Ge disc that rotates below the nozzle. After the sample is collected, the disc is transferred to an FTIR spectrometer where the infrared spectrum of the sample is collected. Normal GPC sample concentrations (0.1-0.25 wtJvol%) give sufficient sample for useable FTIR signals. All normal GPC solvents can be effectively removed, and the interface works with both low temperature and high temperature GPC applications. 

Five of the fundamentals were observed by Stratton and Nielsen (3) in agreement with those obtained by Morgan et al. ( ). The estimated frequency was based upon the observed value of 857.4 cm for the fundamental in the infrared spectrum of the deuterated compound and the application of the Teller-Redlich Isotope rule. The principal moments of inertia are ... 

The application of nmr spectroscopy to hydrocarbons needs no special discussion beyond that already given in Sees. 13.6-13.11. For hydrocarbons as for other kinds of compounds, c shall find that where the infrared spectrum helps to tell us what kifui of compound we are dealing with, the nmr spectrum will help to tell us what compound. 

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