UV-Vis analysis

A systematic study was carried out using in parallel 50 standard solutions for each concentration of three natural colorants (curcumin, carminic acid, and caramel as yellow, red, and brown, respectively). No false positive results for synthetics were obtained up to concentrations of 15 and 20 ng/ml for natural red and yellow colorants, respectively, or 110 ng/ml for natural brown colorant. The concentrations have to be high enough to prove that the screening method is able to accurately discriminate natural and synthetic colorants. To make a clear interpretation of the quantitative UV-Vis spectrum, linear regression analysis was used. Quantitative UV-Vis analysis of a dye ° can be calculated according to the following formula ... 

Robustness for UV-Vis Analysis. Wavelength accuracy, wavelength repeatability, diluting solvent (i.e., pH, concentration), solution stability, and bubble formation by the sipper can be investigated during validation of the analytical component. 

Specificity. For HPLC analysis, resolution of the drug substance from any potential excipient and system interference peaks should be demonstrated. For a UV-Vis analysis, the absorption of the placebo solution should not be significant. It is important to note that the dissolution test is not intended to be stability indicating and will not need to be able to separate degradation peaks from the analyte peak. 

Sample degradation during and after the dissolution process can change the sample solution response compared to standards depending on the absorptivity of the degradant if direct UV-Vis analysis is used. 

Figure 23.11 UV-vis analysis of photocontrolled ion-binding, (a) Regeneration of spiropyran and meiocyanine—Co2+ complex in acetonitrile through the following steps (1) spiropyran, (2) merocyanine, (3) complex, (4) spiropyran, (5) complex, (b) Cycling of spiropyran to merocyanine and generation of merocyanine-Cu2+ complex on SP-modified surface, 560 nm (dashed line) and 431 nm (full line).

Kuruc, J. Sahoo, M. K. Locaj, J. Hutta, M. Radiation degradation of waste waters. I. Reverse phase-high performance liquid chromatography and multicomponent UV-VIS analysis of gamma-irradiated aqueous solutions of nitrobenzene, J. Radioanal. Nucl. Chem. 1994, 183, 99. 

In native VCPO, the position and intensity of cofactor-induced absorption are sensitive to pH change at pH 5, the band is blue-shifted (Xmax 308 nm), and the intensity is decreased to e = 2.0 mM-1 cm-1. The exact correlation between the above-mentioned spectral features and the known X-ray data are complex, but a further UV-VIS analysis of several mutants of this enzyme showed the importance of several structural elements. A His496Ala mutant showed no optical spectrum (Hemrika et al. 1999), whereas crystal structure of this mutant showed the presence of tetrahedral vanadate in the active site (Macedo-Ribeiro et al. 1999), indicating that the V— N bond is crucial for the observed spectrum. The effect of other mutations can be seen in Table 1.1. 

Using fiber optics, Groothaert et al. (2003a) monitored the decomposition of NO and of N2O on CuZSM-5. A bis(/i-oxo)dicopper species, [Cu2(iu-0)2]2+, which had been previously identified by XAFS and UV-vis analysis (Groothaert et al., 2003b), was proposed to be a key intermediate and 02-releasing species. Although no quantitative correlation was established between decomposition rate and intensity of the absorption band of the copper species, the performance appeared to be related to the intensity of this band. 

To evaluate the best ratio between acceptor and donor groups, we carried out a UV-Vis analysis of chloroform solutions of the complex, with a concentration of donor and/or acceptor groups of 0.05 N. The spectra of the two primary products and of the charge transfer complex are presented on Fig. 4. 

Acknowledgments The authors gratefully acknowledge Dr. Martin In for fruitful discussions on rheology experiments and Pascale Guiffrey for UV-Vis analysis. Rhodia silicones company is also acknowledged for the gift of the hydroxypropyl PDMS. 

Infrared and UV/vis data have been used by several authors to identify the C=C, C=0, and M—O stretches in the complexes synthesized 15, 18-21, 37, 38, 41, 44, 50, 54, 56, 58, 59, 64-66, 69, 74, 78, 80, 82, 103). Except in the initial research on first-row transition metal complexes of squaric acid, where these data were used in proposing structures, IR and UV/vis analysis have been used as supporting evidence for the particular coordination mode of the ligand 19,21,22, 45, 52, 59, 65). Infrared spectroscopy has also been utilized in the study of mixed oxalate/squarate complexes 118), although not to the same extent as in complexes of the oxalate ion. For example, Scott et al. studied the IR properties of Co(III) oxalate complexes with the hgand in a variety of chelating/bridging situations 119). 

Ultraviolet-visible (UV-Vis) analysis was performed in the course of electrolyses in aprotic solvents to follow the formation of entities issued from the reduction of sulfur. At the beginning of electrolysis, the formation of 83 and Sg" was clearly evidenced [284]. For larger amounts of electricity, 84 was found to predominate in the cathodic bulk. 

UV-Vis analysis of the effluent liquid showed no significant change in conversion level of reactant and intermediates during experiment I, II and III. 

UV-Vis spectra of the titanium containing MCM-41 and disordered mesoporous titanosilicate samples are shown in Fig. 2. The UV-Vis analysis of these samples show a band near 220 nm range due to tetrahedrally coordinated Ti. Generally a shoulder at -330 nm is expected in the spectrum if the sample contains some bulk titania, but such a shoulder could not be observed. Absorption band at 260-270 nm has been generally attributed to the presence of Ti atoms in 5- and 6- fold coordinations, which are most likely generated through hydration of the tetrahedrally coordinated sites [24]. Ti/Ti-MCM-41 and TiO-SiO(2) samples with higher Ti content than that for the other titanosilicate samples studied here show broader UV-Vis bands with some red-shift. 

The Uv-vis analysis was performed on a Shimadzu UV 210IPC by diffuse reflectance technique in the range 200-600 nm and absorbance between (-0.05) to (-K).75). 

Ultraviolet and visible light (UV-VIS) analysis is the most used identification technique for anthraquinones. The UV-VIS absorption spectrum of an anthraquinone is a combination of the absorptions arising from partial acetophenone- and benzoquinone chromophores (Fig. (7)) [1,20,62]. 

Finally we mention the study of Aguilar-Martinez et al. who synthesised and analyzed the substituent effects on the redox properties of 19 compounds of 3 -(meta) and A - para) substituted 2- (i -phenyl)amine -1,4-naphtalenediones in acetonitrile.153 Beside an UV-vis analysis and a voltammetric study the authors performed semi-empirical (PM3) and DFT calculations (B3LYP with double-C... 

BenBettaieb et al. [188] displayed the effect of electron beam accelerator doses (0, 20, 40 and 60 kGy) on structural, mechanical and barrier properties of edible lightly plasticized chitosan-fish gelatin blend film. UV-vis analysis showed that all films displayed an absorbance peak between 280 and 385 nm. These peaks are shifted toward higher wavelengths after irradiation. This clearly showed some modifications in the interactions (hydrogen bonds, amide groups) between polymer chains induced by the irradiation. 

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