Applications of FT-IR Spectroscopy

The equation above describes the major factors that influence the stretching frequency of a covalent bond between two atoms of masses and mj, respectively. 

The force constant (/) is proportional to the strength of the covalent bond Unking fUi and m2- In the analogy of a spring, it corresponds to the spring s stiffness. 

For example, a C=N double bond is about twice as strong as a C-N single bond, and the CsN triple bond is similarly stronger than the double bond. The infrared stretching frequencies of these groups vary in the same order, ranging from 1100 cm for C-N, to 1660 cm for C=N, to 2220 cm for C=N. 

There are several commercial libraries and many books Usting the vibrational frequencies of thousands of IR spectra of organic and inorganic compounds. 

FT-IR spectroscopy is a suitable spectroscopic technique for pigment analysis since it does not require solubilization of these highly insoluble compounds. The technique is fast, easy to use, and does not require highly trained spectroscopists. 

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Urban MW, Gaboury SR, McDonald WF, Tiefenthaler AM (1990) Adv Chem Ser 227 287 Urban MW, Koenig JL (1990) Recent Developments in Depth Profiling from Surfaces Using FT-IR Spectroscopy. In Durig JR (ed) Applications of FT-IR Spectroscopy, Vibrational Spectra and Structure, vol 18, p 127... 

Substituted thioureas, iso thiocyanates258, thiophenes259 and imidazole-2-thiones260 also form stable self-assembled layers on the gold surface. Tetramethylurea layers can be imaged with STM261. Application of FT-IR spectroscopy to these layers shows that the... 

There is no question that one of the most exciting areas of application of FT-IR spectroscopy has come about because of the time advantage that is gained in the interferometric method for obtaining an IR spectrum, i.e. -the real time coupling of an infrared spectrometer to a gas chromatograph was finally realized. Not only the packed column GC separation, but now also capillary GC separations have benefited from the identification power of the FT-IR spectrometer. An excellent review of GC/FT-IR applications is by Erickson, as well as in the special issue of the Oournal of Chromatographic Science For all these applications, special attention... 

M.K. Antoon, K.M. Starkey and J.L. Koenig, "Applications of FT-IR Spectroscopy to Quality Control of the Epoxy Matrix", ASTM Spec. Tech. Publ. 1979, STP 674, pp. 341-52. 

On a totally different front, we have recently completed some work on the application of FT-IR spectroscopy in the assignment of the V(C0) modes in metal carbonyls [e.g. , M2(CO)iO, M = Mn, Re] through the use of nematic liquid crystals and polarized infrared radiation. Such V(C0) modes occur in the neighbourhood of 2000 cm l, in a region relatively free from the absorptions of the liquid crystal solvents. Fig. 3 depicts the FT-IR (polarized parallel and perpendicular) of Mn2(CO)io dissolved in a room temperature liquid crystal... 

Other recent applications of FT-IR in pharmaceutical analysis include reaction monitoring by fiberoptic FT-IR/ATR spectroscopy140 and stability studies of pharmaceutical emulsions using FT-IR microscopy.141 A novel equipment cleaning verification procedure using grazing angle fiberoptic FT-IR reflection-absorption spectroscopy was described by Perston et al.142... 

FT-IR has almost become a ubiquitous technique in physical and analytical chemistry and a number of sources can be consulted for details 3,4 5,S). This review will only consider those applications related to polymer systems. A number of prior reviews of the applications of FT-IR have been written The relevant theory of vibrational spectroscopy of polymers will not be covered here as it has been treated in detail in a recent monograph15). An excellent discussion of the experimental aspects of the spectroscopy of polymers is also recommended 16). 

Bilayers. A considerable body of literature exists on the application of FT-IR (and Raman) spectroscopy to characterization of the phase behavior of both naturally occurring and synthetic phospholipids. Such compounds have the structure typified... 

P. R. Solomon, P. L. Chien, R. M. Carangelo, P. E. Best, and J. R. Markham, Application of FT-IR Emission/Transmission (ET) Spectroscopy to Study Coal Combustion Phenomena, Twenty-Second Symposium (International) on Combustion, Combustion Institute, pp. 211-221,1988. 

Mathematical modeling of the cure process coupled with the automation of various thermal analytical instruments and Fourier Transform Infrared Spectroscopy (FT-IR) have made possible the determination of quantitative cure and chemical reaction kinetics from a single dynamic scan of the reaction process. This paper describes the application of FT-IR, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) in determining cure and reaction kinetics in some model organic coatings systems. 

Jurdana LE, Ghiggino KP, Leaver IH, and Cole-Clarke P (1995) Application of FT-IR step-scan photoacoustic phase modulation methods to keratin fibres. Applied Spectroscopy 49 361-366. 

One further application of FT-IR imaging spectroscopy is its combination with DSC. As well as allowing the detection of phase separation in polymer blends (as described above), information on the state of order in blend films also becomes... 

In principle, emission spectroscopy can be applied to both atoms and molecules. Molecular infrared emission, or blackbody radiation played an important role in the early development of quantum mechanics and has been used for the analysis of hot gases generated by flames and rocket exhausts. Although the availability of FT-IR instrumentation extended the application of IR emission spectroscopy to a wider array of samples, its applications remain limited. For this reason IR emission is not considered further in this text. Molecular UV/Vis emission spectroscopy is of little importance since the thermal energies needed for excitation generally result in the sample s decomposition. 

Recent work in our laboratory has shown that Fourier Transform Infrared Reflection Absorption Spectroscopy (FT-IRRAS) can be used routinely to measure vibrational spectra of a monolayer on a low area metal surface. To achieve sensitivity and resolution, a pseudo-double beam, polarization modulation technique was integrated into the FT-IR experiment. We have shown applicability of FT-IRRAS to spectral measurements of surface adsorbates in the presence of a surrounding infrared absorbing gas or liquid as well as measurements in the UHV. We now show progress toward situ measurement of thermal and hydration induced conformational changes of adsorbate structure. The design of the cell and some preliminary measurements will be discussed. 

NMR) [24], and Fourier transform-infrared (FT-IR) spectroscopy [25] are commonly applied methods. Analysis using mass spectrometric (MS) techniques has been achieved with gas chromatography-mass spectrometry (GC-MS), with chemical ionisation (Cl) often more informative than conventional electron impact (El) ionisation [26]. For the qualitative and quantitative characterisation of silicone polyether copolymers in particular, SEC, NMR, and FT-IR have also been demonstrated as useful and informative methods [22] and the application of high-temperature GC and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is also described [5]. 

Brown, J. M. Elliott, J. J. "The Quantitative Analysis of Minerals by Fourier Transform Infrared (FT-IR) Spectroscopy", from Workshop on Application of IR Methods to the Study of Clay Minerals, Clay Mineral Society, 20th Annual Meeting, October 1, 1983, Buffalo, NY. 

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... 

Due to the complexity of DOM fractionation has revealed more detailed information on the structural subunits prior to the application of advanced analytical methods. Most effective is the combination of different spectroscopic methods using UV-vis absorbance, fluorescence, 1H- and 13C-nuclear magnetic resonance, and Fourier transform-infrared (FT-IR) spectroscopy. In some studies, also electron paramagnetic resonance spectroscopy (EPR) is used (e.g., Chen et al., 2002). 

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