Ultraviolet absorption and fluorescence

FBAs can also be estimated quantitatively by fluorescence spectroscopy, which is much more sensitive than the ultraviolet method but tends to be prone to error and is less convenient to use. Small quantities of impurities may lead to serious distortions of both emission and excitation spectra. Indeed, a comparison of ultraviolet absorption and fluorescence excitation spectra can yield useful information on the purity of an FBA. Different samples of an analytically pure FBA will show identical absorption and excitation spectra. Nevertheless, an on-line fluorescence spectroscopic method of analysis has been developed for the quantitative estimation of FBAs and other fluorescent additives present on a textile substrate. The procedure was demonstrated by measuring the fluorescence intensity at various excitation wavelengths of moving nylon woven fabrics treated with various concentrations of an FBA and an anionic sizing agent. It is possible to detect remarkably small differences in concentrations of the absorbed materials present [67]. 

Visible and Ultraviolet Absorption and Fluorescence Excitation and Emission Characteristics of Florida Orange Juice and Orange Pulpwash... 

Visible and ultraviolet absorption and fluorescence spectra, obtained from alcoholic solutions of a commercially packed (out of the State of Florida) FCOJ, are presented in Fig. 9, 10, 11 and 12. Qualitatively, Fig. 9 reveals a lack of resolution in the visible absorption region and a well resolved peak at 280 nm. Comparison with Fig. 1 and 3 shows its absorption characteristics to be more similar to those of orange pulpwash in Fig. 3, indicating adulteration by pulpwash addition. Fluorescence excitation spectra (Fig. 10, 11) reveal well defined peaks at 270-75 nm, and Fig. 12 a shoulder at 270-75 nm. The spectra appear deformed when compared to Fig. 2 and 4 of pure orange juice. However, characteristics are similar to those obtained from pulpwash and very similar to those obtained from prepared model systems. Qualitatively both visible and ultraviolet absorption, and room temperature fluorescence indicate the presence of pulpwash in the FCOJ sample. The spectra are complementary. Absorption also did not indicate further adulteration by dilution which would have been denoted by weaker overall absorption and a shift at 227 nm to shorter wavelength. The sum of absorption at 443, 325 and 280 nm is 0.098 + 1.040 + 1.622 = 2.760 absorbance units. Florida State statute 20-64.07(l)(a) requires FCOJ to be 44.8° Brix which reconstituted to 12.8° Brix (16) and Federal standards, Section 52.2582(a), require 41.8° Brix, reconstituted to not less than 11.8° Brix (17). Therefore, the sum of absorbance is multiplied by the ratio of 12.8 to 11.8° Brix, with a corrected sum of 2.995. The sample absorbance ratio at 443/325 nm is 0.098/1.040 which is equal to 0.094. If the sum and natural log ratio values are substituted into the regression equation ... 

Many surfactants, e.g. benzenesulphonates, contain aryl groups and it is found that they will form charge-transfer complexes with 1,2,4,5-tetracyano-benzene which can be detected by ultraviolet absorption and fluorescence spectroscopy (Masuhara et al., 1979) a similar result was obtained with an amphiphatic system. Fluorescence quenching in such micelles has been studied, an example being the quenching of the fluorescence of benzyl anthroate by triethylamine in Triton X (Costa and Macanita, 1978). 

Photothermal dehydrochlorination of PVC as studied by derivative ultraviolet absorption and fluorescence analysis techniques has shown that carbonyl and hydroperoxide groups are more important in the initiation steps than... 

Nakashima K, Akiyama S, Tsukamoto S, Imai K. Synthesis of pyrimido [5,4-d] pyrimidine derivatives and their ultraviolet absorption and fluorescence spectral properties. Dye Pigment 1990 12 21. 

It should not be assumed that all simple mixtures can be analyzed by either of the above techniques. Consider the aromatic hydrocarbon pyrene in the presence of an equal amount of anthracene. The ultraviolet absorption (and fluorescence excitation) spectrum of anthracene completely overlaps that of pyrene. It can be... 

Chen, R., Johnson, J.M., Bradforth, S.E., and Hogen-Esch, TJi. (2003) Ultraviolet absorption and fluorescence emission spectroscopic studies of macrocyclic and linear poly(9,9-dimethyl-2-vinylfluorene). Evidence far ground-state chromophore interactions. Macromolecules, 36,9966-9970. 

Absorption and Fluorescence Spectra. The absorption spectra of actinide and lanthanide ions in aqueous solution and in crystalline form contain narrow bands in the visible, near-ultraviolet, and near-infrared regions of the spectmm (13,14,17,24). Much evidence indicates that these bands arise from electronic transitions within the and bf shells in which the Af and hf configurations are preserved in the upper and lower states for a particular ion. 

The preceding empirical measures have taken chemical reactions as model processes. Now we consider a different class of model process, namely, a transition from one energy level to another within a molecule. The various forms of spectroscopy allow us to observe these transitions thus, electronic transitions give rise to ultraviolet—visible absorption spectra and fluorescence spectra. Because of solute-solvent interactions, the electronic energy levels of a solute are influenced by the solvent in which it is dissolved therefore, the absorption and fluorescence spectra contain information about the solute-solvent interactions. A change in electronic absorption spectrum caused by a change in the solvent is called solvatochromism. 

When porphyrins dissolved in strong mineral acids or in organic solvents are illuminated by ultraviolet hght, they emit a strong red fluorescence. This fluorescence is so characteristic that it is often used to detect small amounts of free porphyrins. The double bonds joining the pyrrole rings in the porphyrins are responsible for the characteristic absorption and fluorescence of these compounds these double bonds are absent in the porphyrinogens. 

Solinova V, Kasicka V, Koval D et al (2004) Analysis of synthetic derivatives of peptide hormones by capillary zone electrophoresis and micellar electrokinetic chromatography with ultraviolet-absorption and laser-induced fluorescence detection. J Chromatogr B 808 75-82... 

In most cases, the linear absorption is measured with standard spectrometers, and the fluorescence properties are obtained with commercially available spectrofluo-rometers using reference samples with well-known <1>F for calibration of the fluorescence quantum yield. In the ultraviolet and visible range, there are many well-known fluorescence quantum yield standards. Anthracene in ethanol (Cresyl Violet in methanol (commonly used reference samples for wavelengths of 350-650 nm. For wavelengths longer than 650 nm, there is a lack of fluorescence references. Recently, a photochemically stable, D-ji-D polymethine molecule has been proposed as a fluorescence standard near 800 nm [57]. This molecule, PD 2631 (chemical structure shown in Fig. 5) in ethanol, has linear absorption and fluorescence spectra of the reference PD 2631 in ethanol to... 

The ultraviolet spectrum of the monosodium salt of luminol shows the absorptions of both the mono- and the dianion of luminol on addition of potassium tert. butylate the equilibrium is shifted to the dianion109). On the other hand, even small quantities of water shift the equilibrium back to the monoanion. The luminol dianion Lum2< ) was found to have a higher fluorescence efficiency than the monoanion. Absorption and fluorescence data for luminol, Lum< > and Lum2< > are listed in Table 4. 

The molecular absorption intensity of polar compounds is usually small, but highly sensitive detection can be obtained after pre- or post-column derivatiza-tions. The use of ultraviolet absorption or fluorescence-active counter-ions makes it possible to achieve highly sensitive detection of polar compounds and enhance the capability of ion-pair liquid chromatography. For example, N,N-dimethylprotriptyline has been used as a counter-ion for carboxylic acids12 and picric acid for quaternary amines13 in normal-phase ion-pair partition liquid chromatography. Phenethylammonium, cetylpyridinium, l-phenethyl-2-pyco-linium, and naphthalene-2-sulfonic acid have been used for sulfonic acid and alkyl amines detection.14,15 Ion-pair post-column extraction was applied on-line for fluorescence detection.16... 

In liquid chromatographic analysis of quinolone antibacterials, most popular is the fluorometric detector due to the inherent fluorescence of these drugs and the advantages in terms of selectivity and sensitivity that this detector offers (Table 29.6). Fluorometric detection after postcolumn derivatization with sulfuric acid has also been reported (203). However, quinolones exhibit also remarkable ultraviolet absorption and are therefore ideal for direct determination without derivatization. Detection can be performed in the wavelength range of 254-295 nm. 

The primary process in the vacuum ultraviolet photolysis of methylene iodide has been studied by Style and Ward,12 who observed that irradiation with light of wavelength 1250-2000 A. excites the fluorescence spectrum of iodine. Attempts to observe any appreciable delay between light absorption and fluorescence were unsuccessful, and the intensity of fluorescence was directly proportional to the light intensity and the pressure of methylene iodide. It was concluded that the excited I2 was produced in the primary process,... 

Absorption and Fluorescence Spectra. The absorption spectra of actinide and lanthanide ions in aqueous solution and in crystalline form contain narrow bands in the visible, near-ultraviolet, and near-infrared regions of the spectrum. 

In the benzotriazole series, examples have been reported in which the benzo ring is substituted with methyl, alkoxy, phenoxy, and also chloro groups, whereby in particular the alkoxy groups exert a decisive effect on the position of the ultraviolet absorption and the fluorescence bands... 

The purpose of this presentation is to discuss the visible and ultraviolet absorption and room temperature fluorescence characteristics of alcoholic solutions of Florida produced orange juice and pulpwash samples, and to relate the characteristics to qualitative detection and quantitative approximation of adulteration of frozen concentrated and single-strength orance juices. Experimental details of our procedures may be found elsewhere (15). 

Visible and ultraviolet absorption and room temperature fluorescence excitation and emission spectra obtained from alcoholic... 

In conclusion, it has been shown that the visible and ultraviolet absorption, and room temperature fluorescence spectra, obtained from alcoholic solutions of orange juice and related products, may be used for product characterization. The complementary absorption and fluorescence spectra may be utilized for the qualitative detection of adulteration of reconstituted frozen concentrated and single-strength orange juice with pulpwash. Previous investigations (chemical and elemental profile analyses)... 

A ferric NHase from Rhodococcus sp. N-771 [54], which is probably the same as that from Rhodococcus sp. N-774 because of the coincidence in amino acid sequences, shows a photosensitive phenomenon both in vivo and in vitro [55,56], Its NHase activity is increased by exposure to near ultraviolet light. Absorption and fluorescence spectra indicated that the chromophore involved in the photoactivation is the iron complex. Crystallographic parameters of the Rhodococcus sp. N-771 NHase have been determined by precision X-ray diffraction studies [57]. 

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