Spectroscopic methods Raman spectroscopy

See also Blood and Plasma. Clinical Analysis Glucose. DNA Sequencing. Fluorescence Overview. Forensic Sciences Drug Screening in Sport. Microscopy Techniques Electron Microscopy Scanning Electron Microscopy Atomic Force and Scanning Tunneling Microscopy. Nucleic Acids Spectroscopic Methods. Raman Spectroscopy Instrumentation. Sensors Overview. 

Among a variety of spectroscopic methods, vibrational spectroscopy is most commonly used in structural chemistry. IR/Raman spectroscopy provides information about molecular symmetry of relatively small molecules and functional groups in large and complex molecules. Furthermore, Raman spectroscopy enables us to study the structures of electronically excited molecules and unstable species produced by laser photolysis at low temperatures. Several other applications that are important in structural chemistry are also discussed in this section. 

Raman Spectroscopy as a Method for Studying Petroleum Fuels Building on previous Raman spectroscopic studies of xylenes. Cooper et al. [89] demonstrated that when the spectra were analyzed using PLS methods, Raman spectroscopy was useful for studying BTEX concentrations (benzene, toluene, ethylbenzene and xylene isomers) of mock petroleum fuels and, subsequently, for actual petroleum products [92], In Fig. 22, representative spectra of selected BTEX materials are shown. The initial work was conducted in the analytical laboratory but has been extended to field operation [92,93]. 

Thus, a more complete study of the spectral properties and the structure of intermediates frozen in inert matrices is achieved when the IR, Raman, UV and esr spectroscopic methods are mutually complementary. Since IR spectroscopy is the most informative method of identification of matrix-isolated molecules, this review is mainly devoted to studies which have been performed using this technique. 

High performance spectroscopic methods, like FT-IR and NIR spectrometry and Raman spectroscopy are widely applied to identify non-destructively the specific fingerprint of an extract or check the stability of pure molecules or mixtures by the recognition of different functional groups. Generally, the infrared techniques are more frequently applied in food colorant analysis, as recently reviewed. Mass spectrometry is used as well, either coupled to HPLC for the detection of separated molecules or for the identification of a fingerprint based on fragmentation patterns. ... 

With recent developments in analytical instrumentation these criteria are being increasingly fulfilled by physicochemical spectroscopic approaches, often referred to as whole-organism fingerprinting methods.910 Such methods involve the concurrent measurement of large numbers of spectral characters that together reflect the overall cell composition. Examples of the most popular methods used in the 20th century include pyrolysis mass spectrometry (PyMS),11,12 Fourier transform-infrared spectrometry (FT-IR), and UV resonance Raman spectroscopy.16,17 The PyMS technique... 

The identification of xanthophylls in vivo is a complex task and should be approached gradually with the increasing complexity of the sample. In the case of the antenna xanthophylls, the simplest sample is the isolated LHCII complex. Even here four xanthophylls are present, each having at least three major absorption transitions, 0-0, 0-1, and 0-2 (Figure 7.4). Heterogeneity in the xanthophyll environment and overlap with the chlorophyll absorption add additional complexity to the identification task. No single spectroscopic method seems suitable to resolve the overlapping spectra. However, the combination of two spectroscopic techniques, low-temperature absorption and resonance Raman spectroscopy, has proved to be fruitful (Ruban et al., 2001 Robert et al., 2004). 

A major emerging area of research activity in interfacial electrochemistry concerns the development of in-situ surface spectroscopic methods, especially those applicable in conventional electrochemical circumstances. One central objective is to obtain detailed molecular structural information for species within the double layer to complement the inherently macroscopic information that is extracted from conventional electrochemical techniques. Vibrational spectroscopic methods are particularly valuable for this purpose in view of their sensitivity to the nature of intermolecular interactions and surface bonding as well as to molecular structure. Two such techniques have been demonstrated to be useful in electrochemical systems surface-enhanced Raman spectroscopy... 

Many methods have been developed to detect the Lewis acidity/basicity and Bronsted acid-ity/basicity. Liquid- or gas-phase titration, UV spectroscopy, and calorimetry are some of the non-spectroscopic methods of detecting acidity and basicity of an oxide material.26 However, we shall confine our discussion to the spectroscopic methods of detecting the acidity and basicity of an oxide material. IR, Raman, and NMR are the common spectroscopic techniques used to quantify the acidity or basicity of an oxide material. 

Y. Matsuda, M. Hachiya, A. Fujii, and N. Mikami, Stimulated Raman spectroscopy combined with vacuum ultraviolet photoionization Application to jet cooled methanol clusters as a new vibrational spectroscopic method for size selected species in the gas phase. Chem. Phys. Lett. 442, 217 219 (2007). 

The studies of Tallin and Buehler indicate that microparticle spectroscopic techniques can be used to follow gas/microparticle chemical reactions. The use of morphological resonances to determine the refractive index of a reacting droplet has limited applicability because there must be a unique relationship between composition and refractive index to allow the method to be used to follow chemical reactions. Raman spectroscopy has broader applications, but one must deal with morphological resonances if droplets are... 

Vibrational spectroscopy, in the form of mid-IR, NIR and Raman spectroscopy has been featured extensively in industrial analyses, both quality control (QC), process monitoring applications and held-portable applications [1-6]. The latter has been aided by the need for advanced instrumentation for homeland security and related HazMat applications. Next to chromatography, it is the most widely purchased classihcation of instrumentation for these measurements and analyses. Spectroscopic methods in general are favored because they are relatively straightforward to apply and to implement, are rapid in terms of providing results, and are often more economical in terms of service, support and maintenance. Furthermore, a single spectrometer or spectral analyzer, in a near-line application, may serve many functions, whereas chromatographs (gas and liquid) tend to be dedicated to only a few methods at best. 

---