Infrared spectroscopic techniques

Beden B 1995 On the use of in situ UV-visible and infrared spectroscopic techniques for studying corrosion products and corrosion inhibitors Mater. Sc/. Forum 192-4 277... 

The objective of this study is to investigate the mechanism of propylene oxidation by a transient infrared spectroscopic technique over Rh/Al203. This technique allows simultaneous measurement of the dynamics of adsorbed species by in situ infrared spectroscopy and the product formation profile by mass spectrometry. 

Newman S., Stolper E.M., and Epstein S. (1986) Measurement of water in rhyolitic glasses calibration of an infrared spectroscopic technique. Am. Mineral. 71, 1527-1541. 

Thosar, S.S. Forbes, R.A. Ebube, Y.C. etal., A comparison of reflectance and transmittance near-infrared spectroscopic techniques in determining drug content in intact tablets Pharm. Dev. Tech. 2001, 6, 19-29. 

Paradkar, M. M., Sivakesava, S., and Irudayaraj, J. (2003). Discrimination and classification of adulterants in maple syrup with the use of infrared spectroscopic techniques. ]. Sci. Food Agric. 83, 714-721. 

New infrared spectroscopic techniques which are used to investigate the benzene/water cluster show an O—H % hydrogen bond184, similar to that of the NH2 n bond. 

Knowledge of the composition and coverage of the attached layer is vitally important to our investigations. Previous work on monolayers of silanes have employed x-ray photoelectron spectroscopy (XPS) as a probe (2-7). XPS confirms the presence of silicon after the reaction and also allows an estimation of the layer thickness. We have used an infrared spectroscopic technique (8, 9 10) which provides complementary information on the nature of the surface layer. 

It is noteworthy to add that the enantiomeric composition determination method based on chiral IL is not specific to near-infrared spectroscopic technique but is rather general as it can be used with other spectroscopic techniques as well. In fact, we have successfully demonstrated that fluorescence technique can also be used with this method. Furthermore, the fluorescence based method has relatively higher sensitivity and lower limit... 

Typical spectral peaks to aid in the identification of coating elastomers and rubbers are shown in Tables 7.4 and 7.5 (Verleye et al., 2001). The tables show that the infrared spectroscopic technique is invaluable in detecting characteristic peaks to identify the differences between chemically similar hydrocarbon polymers, such as polyolefins, natural and butyl rubbers. It is also sensitive enough to show the difference between polyester and polyether urethanes. Modem FUR machines can store, retrieve and compare spectra to enable manufacturers to check quality, identity and characteristics of the polymer materials they use (RAPRA, 2004). 

The authors recognize that some of the results presented in this paper parallel published findings based on other types of infrared spectroscopic techniques, but feel that their presentation in the context of this paper serves to establish the credibility of the DRIFT/GC/MS procedure in advance of the publication of similar studies currently under way on other molecular sieve systems that have not been investigated in detail by such methods. 

Infrared spectroscopic techniques have long been used to analyze gas streams in industrial chemical processes. Recently, with the advent of fastscan infrared spectrometers, they have been used as gas chromatograph detectors. One requirement of their use, needless to say, is that the compound must possess one or more infrared absorption band. By means of a carrier gas. the evolved gas sample from a pyrolysis chamber can be readily passed through an infrared cell for analysis. Infrared systems that can be employed include (1) nondispersive analyzers, (2) dispersion spectrometers. 3) band-pass filter-type instruments, and (4) interference spectrometers all these techniques have been adequately reviewed by Low (87). 

There have been extensive experimental and theoretical studies devoted to the structural and bonding characterization of weakly bound van der Waals complexes of acetylene. Structures of these complexes can often be determinated experimentally by means of Fourier transform microwave and infrared spectroscopic techniques. On the theoretical side, advanced treatments are required to understand the complex nature of the weak bonding in terms of the relative contributions of polarization and dispersion interactions, interactions of multiple moments, and electrostatic interactions involved in these completes. To determine the interaction energy in a weak complex, it is necessary to use large basis sets with the inclusion of electron correlation interactions. Theoretical calculations have been reported for van der Waals complexes of acetylene with COj [160], CO [161, 162], AICI3 [163], NH3 [164], He [165], Ar [166], H2O [167], HCN [168], HF [169-172], HCl [173, 174], and acetylene itself in the forms of non-covalent dimer [175-180], trimer [175,181], tetramer [175, 182, 183], and pentamer [175]. These calculations are very useful for the determination of multiple isomeric forms of the complex. For example, calculations at the MP2/6-31G level along with IR spectra indicate that the HCN-acetylene complex exists in a linear form in addition to the T-shaped structure observed previously by microwave studies (see Fig. 1-5) [168]. 

However, after 1980 the development of in situ infrared spectroscopic techniques have allowed the direct identification of adsorbed intermediates. In terms of methanol oxidation on R, electrochemically modulated infrared reflectance spectroscopy (EMIRS) led to the unambiguous identification of adsorbed CO as the poisoning species. Two adsorbed CO species were identified as being responsible for the poisoning phenomena (i) a linearly bonded species (IR absorption band around 2060 cm ) and (ii) a bridge-bonded species (a small band around 1850-1900 cm ). These results were... 

Table 3. A comparison of infrared spectroscopic techniques for surface analysis (adopted from Ref. [182])...

The VT-DRIFT spectrum of pyridine adsorbed on unmodified silica gel is shown in Figure 29.3, Absorption maxima are observed at 1595, 1485, and 1445 cm According to the assignments made by Parry [16], these bands indicate hydrogen-bond formation. The absorptions result from in-plane C-C stretching modes 8a, 19a, and 19b, respectively [18]. The acidic strength of the surface sites is insufficient to generate pyridinium ion. This observation is consistent with previous studies of silica gel that used transmission infrared spectroscopic techniques [19]. 

F. Hamad, K. C. Khulbe, and T. Matsuura. Interaction of gaseous hydrocarbons with poly(phenylene oxide) membranes by infrared spectroscopic technique. J. Membr. ScL, 204(l-2) 27-36, July 2002. 

To understand how polymer degradation may be monitored by using infrared spectroscopic techniques. 

Domszy, J. G. and G. A. F. Roberts. 1985. Evaluation of infrared spectroscopic techniques for analysing chitosan. Ma romo/. Chem. 186 1671-1677. 

Further insight into the nature of the interaction between irreversibly adsorbed species and the filler surface can be gained from DRIFTS analysis of the filler sample taken from the FMC cell after completion of the adsorption - desorption cycle. DRIFTS is described in more detail in Section 3.5.4, but in summary, it is an infrared spectroscopic technique, that by virtue of a significant proportion of glancing angle reflections, affords enhanced resolution of filler surface functional groups. The authors have found this technique particularly useful when studying competitive adsorption of polymer stabilisers and carboxylic acids onto silica and metal hydroxides, respectively. 

Evaluation of Infrared Spectroscopic Techniques to Assess Molecular Interactions... 

Oldak and Pearson (106) utilized infrared spectroscopic techniques to assess the molecular interactions of epoxies in the monomeric state. Both carbonyl peak shifts and hydroxyl peak shifts were used to determine the Drago... 

L. K. S0rensen, R. Jepsen. Comparison of near infrared spectroscopic techniques for determination of semi-hard cheese constituents. Milchwissenschefi 53(5) 263-267,1998. 

Structural information on proteins can be obtained with X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy however, due to various limitations intrinsic to these high-resolution structmal methods, only alternate spectroscopic techniques (especially fluorescence, circular dichroism (CD), Raman, and infrared spectroscopic techniques) can be employed for conformational characterization of proteins as well as stabilization and denaturation of enzymes. 

HW Schrotter. Raman and infrared spectroscopic techniques for remote analysis of the atmosphere. In RJH Clark, RE Hester, eds. Advances in Infrared and Raman Spectroscopy, Vol. 8. London Heyden, 1981, pp 1-51. 

The infrared spectrum of the solvent solution can then be obtained by normal infrared spectroscopic techniques. 

N. Sheppard, Recent Advances in Infrared Spectroscopic Techniques, Analyst 77, 732, 1952. 

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