FT Raman spectroscopy

FT-IR spectroscopy has become an established method in solid-phase chemistry, because it is a fast, sensitive and convenient method for monitoring resin-bound reactions with relatively low equipment costs. 

KBr pellet or single bead samples are suitable for the purpose of solid-phase reaction monitoring and the study of reaction kinetics. For the KBr-embedded samples, a higher amount of resin material and longer sample preparation time is required, but these are compensated by the low costs for the measurement with KBr-pellets. The compromise here is the use of an ATR-instrumentation. With this technique the throughput of samples is much higher at low costs for additional equipment. ATR-IR spectra quality is at the same level than for the common methods mentioned before. 

The use of single bead IR spectroscopy is a valuable method for real-time monitoring of reaction kinetics or investigations of small amounts of resin beads. 

The most interesting examination method with IR microscopy is the spatially resolved mapping of resin-bound compound libraries. A non destructive statistical characterization of resin-bound libraries is possible by this method. However, the investment for IR-microscopy is relatively high, especially when used in combination with image analysis. 

Roderick Siifimuth, Axel Trautwein, Hartmut Richter, 

Near-infrared excited FT-Raman spectroscopy has recently begun to show promise (Schrader, 1990), because the fluorescence is drastically reduced. It has the Jaquinot advantage over classical Raman spectroscopy, which affords a better signal-to-noise ratio. FT-Raman is an excellent technique to supplement FTIR difference spectroscopy in investigations of intramolecular protein reactions because Raman spectra have the 

FT techniques have greatly broadened the scope of both IR and Raman spectroscopy. In the near future, these methods are expected to provide a considerable stimulant to studies of time dependent phenomena in complex systems. The stroboscope and step-scan technique are probably also u.seful for FT-Raman. This would be very convenient, since it is relative easy to back up an FTIR instrument with an FT-Raman module. 

Modem high-pressure research encompasses a plethora of fields and has extended applications in physics, chemistry, the geosciences, planetary science, biochemistry, biology, material science, and in engineering, including chemical engineering. The term high pressure in this context refers to pressures of at least a few hundred bars and mostly in excess of one kbar (0.1 GPa). 

Infrared and Raman studies at very high pressure (up to several hundred kbar) are carried out fairly routinely with diamond anvil cells (DAC). The DAC, which was first developed for high-pressure infrared absorption measurements by Weir et al. (1959) and for X-ray studies by Jamieson et al. (1959), has become a very powerful tool for a wide variety of ultra-high pressure investigations, with particularly important applications in solid state physics. The potential of the method has increased enormously with the introduction of gaskets into the DAC by Van Valkenburg (see Jayaraman, 1983) and with the possibility of pressure calibration by the ruby fluore.scence method (Forman et al, 1972). 

For chemical applications, vibrational spectroscopy of high-pressure fluid phases, including liquids and compressed gases, is of special importance (Buback, 1991). The fluid, i.e., the non-solid region of a substance, is illustrated in Fig. 6.7-2. The packing density of the circles is approximately proportional to the density of a substance. The bottom left part of Fig. 6.7-2 shows the vapor pressure curve which, up to the critical point, separates the liquid phase from the gas phase. Above the critical temperature (7 ), the density of a substance may change continuously between gaseous and liquid like states vibrational spectroscopic methods make it possible to study the structure and dynamics 

Wacker-Chemie GmbH, Johannes-Hess-Strasse 24, D-844892 Buighausen, Germany Tel. +49 8677 83 1662 — Fax +49 8677 83 6265 E-mail finnk.baumaim wacker.com 

Keywords FT-raman spectroscopy, hydrosilylation, on-line process control 

Summary The use of the on-line FT-Raman spectroscopy for monitoring a multi-step hydrosilylation reaction combines all the advantages of an on-line analytical tool (like real time measuring results, a direct view into the reaction, and no off-line sample collection) with the requirements for the application of technology in production plants, e. g., low calibration effort within a wide temperature range, stable calibration, simple system handling for the operator, small sized equipment at the reaction vessel, and no contact with the reaction media. 

There are two main success factors for a company in the market from the point of view of the supply chain. One is to bring the product with the right quality at the right time to the customer. The other is to have the best and most cost-effective processes. Therefore, there is always pressure to optimize the processes with respect to both product quality and cost effectiveness 

One excellent tool to fulfill these requirements is an on-line analytical method which allows a direct view into the miming process and give the plant manager a chance to optimize, for example, the general process design, the ranning time of the processes, the raw material usage factor, the catalyst concentration, the overall yield of the process, and the product quality. 

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Nonnal spontaneous Raman scahering suffers from lack of frequency precision and thus good spectral subtractions are not possible. Another limitation to this technique is that high resolution experiments are often difficult to perfomi [39]. These shortcomings have been circumvented by the development of Fourier transfomi (FT) Raman spectroscopy [40]. FT Raman spectroscopy employs a long wavelength laser to achieve viable interferometry. 

Hirschfeld T and Chase B 1986 FT-Raman spectroscopy development and justification Appl. Spectrosc. 40 133-9... 

The infrared laser which is mosf often used in this technique of Fourier transform Raman, or FT-Raman, spectroscopy is the Nd-YAG laser (see Section 9.2.3) operating at a wavelength of 1064 nm. 

In FT-Raman spectroscopy the radiation emerging from the sample contains not only the Raman scattering but also the extremely intense laser radiation used to produce it. If this were allowed to contribute to the interferogram, before Fourier transformation, the corresponding cosine wave would overwhelm those due to the Raman scattering. To avoid this, a sharp cut-off (interference) filter is inserted after the sample cell to remove 1064 nm (and lower wavelength) radiation. 

Friedel-Crafts catalysts, 329, 331 Friedel-Crafts reaction, 297, 361 Front-end reactions, 235 FT Raman spectroscopy, 387 FTIR spectrometry. See Fourier transform infrared (FTIR) spectrometry Fuel cells, 272-273 Full prepolymers, 236, 237 Functionalized polyolefins, 459-460... 

Spectroscopy, 490. See also 13C NMR spectroscopy FT Raman spectroscopy Fourier transform infrared (FTIR) spectrometry H NMR spectroscopy Infrared (IR) spectroscopy Nuclear magnetic resonance (NMR) spectroscopy Positron annihilation lifetime spectroscopy (PALS) Positron annihilation spectroscopy (PAS) Raman spectroscopy Small-angle x-ray spectroscopy (SAXS) Ultraviolet spectroscopy Wide-angle x-ray spectroscopy (WAXS)... 

Schulz, H., Baranska, M., and Baranski, R., Potential of NIR-FT-Raman spectroscopy in natural carotenoid analysis. Biopolymers, 11, 212, 2005. 

The sensitivity limitations of TLC-FT-Raman spectroscopy may be overcome by applying the SERS effect [782]. Unlike infrared, a major gain in Raman signal can be achieved by utilising surface activation and/or resonance effects. Surface-enhanced Raman (SER) spectra can be observed for compounds adsorbed on (rough) metahic surfaces, usually silver or gold colloids [783,784], while resonance Raman (RR) spectra... 

A rapid characterization of the viscosity of waterborne automotive paint was reported by Ito et al. [24], FT-Raman spectroscopy in conjunction with partial least squares regression (PLS) was applied and led to a reasonable correlation. 

Under the synthesis conditions in this study, gels with the organic templates, viz., MCHA, TEA, TPA, and TEAOH form clearly the AlP04-5 structure. The type of the organic template used affects the morphology of the produced crystals due to the different ways of interaction between the template and the host framework, which could be investigated using FT-Raman spectroscopy. 

The molecular natures of salts crystallized from salbutamol base have been assessed by FT-Raman spectroscopy [66]. Variations in vibrational frequencies due to electron-withdrawing or -donating substituents were clearly evident the CCO stretching vibration shifted from 776 cm-1 in the free base to 756 cm-1 in the benzoate salt. The C=C stretching frequency also shifted from 1610 cm-1 to 1603 cm-1 with the benzoate ion but showed an increase to 1616 cm-1 with sulfate ion. Clearly, the choice of salt affects the molecular nature of the drug, with obvious implications for its physicochemical properties. 

Brody, R. H. (2000). Applications of FT-Raman Spectroscopy to Biomaterials. Unpublished Ph.D. Thesis, UK, University of Bradford. 

Rehman, I., Smith, R., Flench, L. L., and Bonfield, W. (1995). Structural evaluation of human and sheep bone and comparison with synthetic hydroxyapatite by FT-Raman spectroscopy. Journal of Biomedical Materials Research 29 1287-1294. 

Recent studies on PEO-PPO, PEO-PBO di- and triblock copolymers include the works of Bahadur et al. [121], who examined the role of various additives on the micellization behavior, of Guo et al. [122], who used FT-Raman spectroscopy to study the hydration and conformation as a function of temperature, of Booth and coworkers [ 123], who were mainly interested in PEO-PBO block copolymers with long PEO sequences, and of Hamley et al., who used in situ AFM measurements in water to characterize the morphology of PEO-PPO micelles [56,57]. 

T.R.M. De Beer, W.R.G. Baeyens, Y. Vander Heyden, J.R Remon, C. Vervaet and F. Verpoort, Influence of particle size on the quantitative determination of salicylic acid in a pharmaceutical ointment using FT-Raman spectroscopy, Em J. Pharm. Sci., 30, 229-235 (2007). 

C. Ricci, L. Nyadong, F. Yang, F.M. Fernandez, C.D. Brown, P.N. Newton and S.G. Kazarian, Assessment of hand-held Raman instrumentation for in situ screening for potentially counterfeit artesunate antimalarial tablets by FT-Raman spectroscopy and direct ionization mass spectrometry. Anal. Chim. Acta, 623, 178-186... 

M. Baranska, H. Schulz, R. Siuda, et al. Quality control of Harpagophytumprocumbens and its related phytop-harmaceutical products by means of NIR-FT-Raman spectroscopy, Biopolymers, 77, 1-8 (2005). 

R. KizU and J. Irudayaraj, Discrimination of irradiated starch gels Using FT-Raman spectroscopy and chemomet-rics, J. Agric. Food Chem., 54, 13-18 (2006). 

C. Bauer, B. Amram, M. Agnely, D. Charmot, J. Sawatzki, M. Dupuy and J.-P. Huvenne, On-hne monitoring of a latex emulsion polymerization by fiber-optic FT-Raman spectroscopy. Part I Cahbration, Appl. Spectrosc., 54, 528-535 (2000). 

B. De Spiegeleer, D. Seghers, R. Wieme, J. Schaubroeck, R Verpoort, G. Siegers and L. Van Vooren, Determination of the relative amounts of three crystal forms of a benzimidazole dmg in complex finished formnlations by FT-Raman spectroscopy, J. Pharm. Biomed. Anal., 39, 275-280 (2005). 

L.E. O Brien, P Timmins, A.C. Williams and P. York, Use of in situ FT-Raman spectroscopy to study the kinetics of the transformation of carbamazepine polymorphs, J. Pharm. Biomed. Anal., 36, 335-340 (2004). 

K. Ito, T. Kato and T. Ona, Rapid viscosity determination of waterborne automotive paint emulsion system by FT-Raman spectroscopy, Vib. Spectrosc., 35, 159-163 (2004). 

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