Raman analyses

Watanabe, H., Ishida, Y., Hayazawa, N Inouye, Y. and Kawata, S. (2004) Tip-enhanced near-field Raman analysis... 

Principles and Characteristics The prospects of Raman analysis for structural information depend upon many factors, including sample scattering strength, concentration, stability, fluorescence and background scattering/fluorescence from the TLC substrate. Conventional dispersive Raman spectroscopy has been considered as a tool for in situ analysis of TLC spots, since most adsorbents give weak Raman spectra and minimal interference with the spectra of the adsorbed species. Usually both silica and cellulose plates yield good-quality conventional Raman spectra, as opposed to polyamide plates. Detection limits for TLC fractions... 

Absorption and Raman analysis of LHCII complexes from xanthophyll biosynthesis mutants and plants containing unusual carotenoids (e.g., lactucoxanthin and lutein-epoxide) should also be interesting, since the role of these pigments and their binding properties are unknown. Understanding the specificity of binding can help to understand the reasons for xanthophyll variety in photosynthetic antennae and aid in the discovery of yet unknown functions for these molecules. 

Typical X-ray diffraction patterns of three different carbon powder samples are shown in Fig. 3. Two 00/ and two hkO diffraction peaks can be distinguished in the patterns of samples produced at 800°C and 1000°C. The 002 (26 26.9°) and 004 (26 54.9°) peaks correspond to the parallel graphene layers. The 100 (26 43°) and 110 (26 77.8°) diffraction peaks are characteristics of the 2D in-plane symmetry along the graphene layers. Based on its XRD pattern, the powder synthesized at 500°C is not graphitized, which is in agreement with Raman analysis. This low temperature sample also contains traces of iron chlorides. 

Further analysis of these XRD profiles shows that the width of the 002 peak decreases as the reaction temperature increases. Its position is approximately the same for both 800°C and 1000°C, which indicates that the graphitic interplanar spacing (0.334 nm) is developed in these powders at temperatures as low as 800°C. This is also in agreement with the TEM and Raman analysis. As the reaction temperature increases, the 101 band also splits into 100 and 101 peaks. 

Li Y.S., Vo-Dinh T., Stokes D.L., Yu W., Surface-enhanced Raman analysis of p-nitroaniline on vacuum evaporation and chemically deposited silver-coated alumina substrates,Appl. Spectrosc 1992 46 1354-1357. 

As an example of the application of joint micro-LIBS and micro-Raman analysis on actual samples, results are reported on the study of a small fragment (less than 1 mm2) of the S.Antonio Abate , a wooden painted artwork decorating the Arciconfratemita della Misericordia in Siena, attributed to the Renaissance Italian artist Domenico di Pace, also known as II Beccafumi (Montaperti 1486 - Siena 1551). The sample, whose dimensions were relatively small (less than 1 mm2), was given by Opificio delle Pietre Dure di Firenze (OPD) to the Department of Chemistry of Pisa University, where it was going to be analysed for the presence of lakes in the... 

Since LIBS analysis doesn t give information about the molecular composition of the pigments, a micro-Raman analysis was performed for an exact characterization of the sample. 

The Raman analysis confirmed this identification. In Figure 8 are reported the Raman spectrum of the blue pigment obtained and the one provided by the UCL database the superimposition of the two spectra is, in this case, about perfect. 

It seems to be likely that by analogy with cyclopropenones the observed absorptions originate from strong coupling of the endo- and semicyclic C=C bonds however a detailed IR and Raman analysis of triafulvenes has not yet been performed. 

Clearly, the potential applications for vibrational spectroscopy techniques in the pharmaceutical sciences are broad, particularly with the advent of Fourier transform instrumentation at competitive prices. Numerous sampling accessories are currently available for IR and Raman analysis of virtually any type of sample. In addition, new sampling devices are rapidly being developed for at-line and on-line applications. In conjunction with the numerous other physical analytical techniques presented within this volume, the physical characterization of a pharmaceutical solid is not complete without vibrational analysis. 

P. Matousek and A.W. Parker, Bulk Raman analysis of pharmaceutical tablets, Appl. Spectrosc., 60, 1353-1357... 

G.J. Gervasio and M.J. Pelletier, On-line Raman analysis of PCI3 reactor material. Journal of Process Analytical Chemistry, III, 7-11 (1997). 

D.E. Pivonka and J.R. Empfield, Real-time in situ Raman analysis of microwave-assisted organic reactions, Appl. 

ExxonMobil Chemical Company, On-line Raman analysis and control of a high pressure reaction system. Inventors D.G. Marrow and D.A. Yahn. 11 pp. (inch 3 fig.). Appl. 22 Jul 2005. Int. Cl. C08G 73/00. US Patent Application Publication 2007/0021586 A1... 

How can we be sure that the U +(Q2-) complex in a mixed metal oxide is present as the UO octahedron This can be done by studying solid solution series between tungstates (tellurates, etc.) and uranates which are isomorphous and whose crystal structure is known. Illustrative examples are solid solution series with ordered perovskite structure A2BWi aUa 06 and A2BTei-a Ua 06 91). Here A and B are alkahne-earth ions. The hexavalent ions occupy octahedral positions as can be shown by infrared and Raman analysis 92, 93). Usually no accurate determinations of the crystallographic anion parameters are available, because this can only be done by neutron diffraction [see however Ref. (P4)]. Vibrational spectroscopy is then a simple tool to determine the site symmetry of the uranate complex in the lattice, if these groups do not have oxygen ions in common. In the perovskite structure this requirement is fulfilled. 

In the geosciences Raman spectroscopy has traditionally been a laboratory tool for structural analysis of minerals. Recent developments in instrumentation make possible the use of Raman spectroscopy as a tool for routine identification of minerals in field situations. The following advantages characterize Raman analysis of minerals no sample preparation in situ real time measurement non-destructive and non-intrusive sampling samples may be transparent or opaque spectra are well resolved and with high information content. 

Raman spectroscopy, while typically used as a micro-analytical tool, can be conducted remotely. Performance of remote Raman analysis have been recently explored and reahzed for experiments on the surface of Mars (Sharma et al. 2001 Sharma et al. 2003). Raman spectroscopy is a powerful technique for mineralogical analysis, where the sharpness of spectral features of minerals allows for much less ambiguous detection, especially in the presence of mixtures. Visible, near-infrared, thermal, reflectance and in many cases emission spectroscopy of minerals all suffer from broad overlapping spectral features, which complicates interpretation of their spectra. On the other hand, Raman spectra of minerals exhibit sharp and largely non-overlapping features that are much more easily identified and assigned to various mineral species. 

In subsequent studies, this first approach was extended by also exposing lead coupons, for they are very sensitive to organic acids. After only a few months of exposure, the surface products could be characterized by performing Raman analysis combined with electrochemical reduction. Results point to the presence of formiates and acetates for the coupons presenting the larger corrosion rates [309]. 

Other sources of error, particularly in quantitative Raman analysis, include laser self-absorption effects leading to attenuation of some spectral bands. Similarly diffuse reflectance of the laser light, which is dependent on the particle size of the formulation components, may increase or decrease the collection volume. However, normalisation techniques can be used to overcome some of these effects [35]. 

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