Ultraviolet-Visible UV-Vis Spectroscopy

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

NMR is not, of course, the only analytical technique used to establish the composition and microstructure of polymeric materials. Others include >66 ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy, and infrared (IR) spectroscopy. IR and Raman spectroscopy are particularly useful, when by virtue of cross-linking (see. e.g. Chapter 9), or the presence of rigid aromatic units (see Chapter 4). the material neither melts nor dissolves in any solvent suitable for NMR. The development of microscopy based on these spectroscopic methods now makes such analysis relatively simple (see below). Space precludes a detailed account of these and many other techniques familiar to the organic chemist. Instead we focus for the remainder of the chapter on some of the techniques used to characterize the physical properties of polymeric materials. 

Ultraviolet-visible spectroscopy (UV = 200 - 400 nm, visible = 400 - 800 nm) corresponds to electronic excitations between the energy levels that correspond to the molecular orbital of the systems. In particular, transitions involving n orbital and ion pairs (n = non-bonding) are important and so UV/VIS spectroscopy is of most use for identifying conjugated systems which tend to have stronger absorptions... 

Ultraviolet and visible spectroscopy (UV-vis) is an analytical technique useful in the investigation of some organic molecules. Absorption of energy in... 

The terms specificity and selectivity are often interchangeably used. A method is said to be specific if it provides a response for only a single analyte. If the response in question is distinguished from all other responses, the method is said to be selective. The International Conference on Harmonization (ICH)-2 does not differentiate both terms and defines specificity or selectivity as the ability to unambiguously determine the analyte in the presence of other components whose presence is to be expected. This includes typical impurities, decomposition products, and matrix components. The specificity of the method for TLC analyses was proved by identification and purity checks of the analyte spots. This can be done by measuring in situ the ultraviolet and visible spectroscopy (UV-VIS) spectra of... 

UVPES, UPS ultraviolet photoelectron spectroscopy UV-VIS, UV-Vis ultraviolet-visible... 

Initially, simple methods such as ultraviolet-visible (UV-Vis), fluorescence or infrared (IR) spectroscopy were proposed in order to estimate the total amount of antioxidants in various food samples. However, coupled methods such as gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography with ultraviolet-visible (HPLC-UV-Vis) or nuclear magnetic resonance detector (HPLC-NMR) and liquid chromatography-mass spectrometry (LC-MS) are employed more to quantify individual tocols or carotens from various corn-based food samples. In this chapter all these methods of analysis will be briefly described. 

The metal content analysis of the samples was effected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES Varian Liberty II Instrument) after microwaves assisted mineralisation in hydrofluoric/hydrochloric acid mixture. Ultraviolet and visible diffuse reflectance spectroscopy (UV-Vis DRS) was carried out in the 200-900 nm range with a Lambda 40 Perkin Elmer spectrophotometer with a BaS04 reflection sphere. HF was used as a reference. Data processing was carried out with Microcal Origin 7.1 software. 

The tautomerism of 4 (Figure 1) was also studied by UV-Vis (ultraviolet-visible) spectroscopy in polar aprotic solvents the effect of added water, darkness, and indirect sunlight were also evaluated. The experimental spectroscopic results are discussed in Section 13.14.3.1.1 (i). Theoretical calculations using ZINDO/S were performed to state the allowed absorption transitions <2005SAA875>. The five tautomeric structures of 4 as well as the calculated energies for each are depicted in Figure 2. 

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