Ultraviolet fluorescence

The most common detectors in HPLC are ultraviolet, fluorescence, electrochemical detector and diffractometer. However, despite all improvements of these techniques it seems necessary to have a more selectivity and sensitivity detector for the purposes of the medical analysis. It should be therefore improvements to couple analytical techniques like infrared IR, MS, nuclear magnetic resonance (NMR), inductively coupled plasma-MS (ICP-MS) or biospecific detectors to the LC-system and many efforts have been made in this field. 

Other techniques to inspect bonding surfaces for contamination have also been proposed, including ultraviolet fluorescence [162], Pulsed ultraviolet light incident on the surface excites fluorescence of organic contamination, which can... 

Reactions Producing Fluorescent Radiation In the reaction chamber of the ultraviolet fluorescent analyzer reactions producing fluorescence are... 

Construction and Operation of Analyzer The construction principle of a sulfur dioxide analyzer based on the ultraviolet fluorescence principle is shown in Fig. 13.48. Undesired wavelengths are removed from the irradiating beam as tar as pos.sible using filters. The irradiating light 214 nm) is focused by a lens at the center of the reaction chamber. 

TRS Converter To measure hydrogen sulfide and reduced-organic sulfur compounds, the technique used is thermal oxidation, in which sulfur dioxide is produced. Hydrogen sulfide and other reduced-sulfur compounds are measured by using methods applicable to the measurement of sulfur dioxide concentrations. One method is a technique based on ultraviolet fluorescence. 

FIGURE 13.48 Schematic of sulfttr dioxide analyrer based on the ultraviolet fluorescence principle... 

Although these reactions suggest the possibility of a tautomeric equilibrium between the amide and imidol forms in the A -unsub-stituted compounds, the ultraviolet,fluorescence, and infrared spectra of a series of such compounds support the amide structure only. 

Guyan et al. 1990) have used several markers of lipid peroxidation (9-cis-, 11-tmns-isomer of linoleic acid, conjugated dienes and ultraviolet fluorescent products) to demonstrate significant increases in the duodenal aspirate after secretin stimulation in patients with acute and clinic pancreatitis. They interpreted this as indicating induction of hepatic and pancreatic drug-metabolizing enzymes in the face of a shortfidl of antioxidant defences, more marked in chronic pancreatitis. Subsequent studies in patients with chronic pancreatitis have confirmed decreased serum concentrations of selenium, -carotene and vitamin E compared with healthy controls (Uden et al., 1992). Basso aol. (1990) have measured increases in lipid peroxides in the sera of patients with chronic... 

Buffered mobile phases are used and the proportions of polar solvents (e.g. methanol, tetrahydrofuran) depend upon the type of derivative employed. Gradient elution is required for the resolution of complex mixtures and analysis times are less than 1 h. Ultraviolet, fluorescence or electrochemical detectors are used depending upon the nature of the amino acid derivatives. 

Hancock and coworicers have studied the photochemistry of a series of compounds in which the -B=N- functional group is the essential chromophore " The -B=N- linkage in aminoboranes is analogous to the isoelectronic (-C=C-) ethylenic linkage in molecules studied extensively by organic photochemists. Many aminoboranes absorb radiation in the near ultraviolet Fluorescence spectra have been reported for a number of compounds with the general formula... 

Colleagues at the Forensic Explosives Laboratory have found the following procedure suitable pre-activated sfrica gel coated plates containing an ultraviolet fluorescent indicator are used. A mixed standard solution is run in one of the channels on the plate, alongside solutions of the samples and blanks. Table 1 shows the recommended eluent systems. 

Trioxsalen and methoxsalen are psoralens used for the repigmentation of depigmented macules of vitiligo. With the recent development of high-intensity long-wave ultraviolet fluorescent lamps, photochemotherapy with oral methoxsalen for psoriasis and with oral trioxsalen for vitiligo has been under intensive investigation. 

Chemical Conversion Methods. Laser-Induced and Resonance Fluorescence of HO. Considerable effort has been applied to the measurement of HO in the stratosphere and troposphere. Ultraviolet fluorescence techniques based on lasers or resonance lamps have received a great deal of attention and study. Because HO concentrations are typically factors of one-tenth to one-hundredth those of H02 in the atmosphere, the difficulties associated with making HO measurements by using fluorescence [low signal-to-noise ratio, laser-generated HO, background fluorescence, etc. see the... 

Detection by Fluorescence. The detection test is the ultraviolet light-activated yellow fluorescence which is induced only after spraying with 70% aqueous sulfuric acid (2). A preliminary inspection under ultraviolet light eliminates substances with non-sulfuric acid-induced ultraviolet fluorescence. In practice, the restriction to yellow eliminates many predominantly blue components in a plant extract chromatogram. Some yellow fluorescent components have been observed on occasion from plant sources without spraying, and are thus eliminated. Few bands have been observed that give a positive test other than at the Rf of GA3 or its decomposition produots. 

Ultraviolet fluorescence spectroscopy has also been employed to investigate the nature of the aromatic systems in coal and in coal-derived products (Mille et al., 1990). Examination of the pyridine extracts produced data that were characteristic of compounds having three, four, or five condensed aromatic rings. However, it was not possible to obtain an estimation of the ring size within the insoluble coal matrix. 

N. R. Srinivas and L. N. Lgwemezie, Chiral separation by HPLC.l. Review of indirect separation of enantiomers as diastero-meric derivatives using ultraviolet, fluorescence and electrochemical detection, Biomed. Chromatogr., 6 163 (1992). 

Cruezwa et al. [168] reported a method in which traces of phenols and cresols in rain waters were determined by continuous liquid-liquid extraction and normal phase high performance liquid chromatography with ultraviolet fluorescence detection. 

At the beginning of the Triad field investigation, only the uppermost two 1 -ft intervals at each location were analyzed in the field. Ultraviolet fluorescence test kits, which require 5 min per sample for collection and analysis, were used for field detection of PAH and TPH at all sampling locations. A percentage of the PAH and TPH samples were sent to an off-site laboratory for independent collaboration of the field results. 

Teale, F.W.J. (1960). The ultraviolet fluorescence of proteins in neutral solution. The Biochemical Journal, 76, 381-388. 

Teale FWJ, Weber G. Ultraviolet fluorescence of proteins. Bio-chem. J. 1959 72 15. 

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