Color quenching

Able to form Ag salt of lower solubility than AgQ in H2O. Therefore applications in photographic processes Inhibition of histidine decarboxylase activity Antifoggant for color films Anthelmintic activity Quenching for oil composition caialj si for the industrial isomerization of cis a, (3 unsaturaied carboxylic acids rubber vul-cankzate improver... 

Color reproduction of the chromatograms can be achieved by color photography — the best, but also the most expensive method of documenting thin-layer chromatograms. It can be used not only to produce true-color reproductions of colored zones but also — with the aid of a Reprostar (Fig. 64) or a UVIS analysis lamp (Fig. 6) — of fluorescent or fluorescence-quenched zones. When photograph-... 

Note In the case of HPTLC plates the detection limit for the visual recognition of the violet = 530 nm) colored chromatogram zones was 20 ng per chromatogram zone. With the exception of the two tetrahydrosteroids the cor-ticosteriods could be detected on TLC plates with fluorescent indicators by reason of fluorescence quenching (Fig. 1 A). Figure 2 illustrates the absorption scans of the separations illustrated in Figures 1A and 1B. 

Acid Color Fluorescence quenching (>l = 254 nm) Sensitivity (pg/zone) TLC HPTLC ... 

Note The alternative fast blue salt BB produced the most intensely colored chromatogram zones for visual analysis in daylight, while fluorescence quenching in UV light (A = 254 nm) was greater with fast blue salt B and fast blue salt RR (Figs. 1 and 2). 

Androst-4-ene-3,17-dione 17a-Hydroxyprogesterone (1 g) is dissolved in 10 ml of pyridine and treated dropwise at —20° with a solution of nitrosyl chloride in pyridine until a permanent blue color develops. The reaction is quenched with 500 ml of ice water, and the resulting nitrite is filtered and... 

Fluorescent small molecules are used as dopants in either electron- or hole-transporting binders. These emitters are selected for their high photoluminescent quantum efficiency and for the color of their emission. Typical examples include perylene and its derivatives 44], quinacridones [45, penlaphenylcyclopenlcne [46], dicyanomethylene pyrans [47, 48], and rubrene [3(3, 49]. The emissive dopant is chosen to have a lower excited state energy than the host, such that if an exciton forms on a host molecule it will spontaneously transfer to the dopant. Relatively small concentrations of dopant are used, typically in the order of 1%, in order to avoid concentration quenching of their luminescence. 

Analysis. Quant detn with Ce(IV), proc a sample contg 3—16mg of PE is mixed with a 50—100% excess of the Ce(IV) reagent, 1 ml of catalyst B and 8.5ml 72% perchloric ac added, the mixt heated on a hot plate at 95° until a pink color develops, the mixt quenched by chilling,... 

If hot sulfur melts or hot sulfur vapors at low pressure are frozen at low temperatures highly colored samples are obtained which may be black, green or red depending on the temperature and pressure conditions and on the rate of quenching [69]. These colors originate from the small molecules and radicals, present at high temperatures, which become trapped in the solid sample. At room temperature these samples turn yellow, provided the sulfur has been very pure. 

Variations of the critical value of Ka with the equivalence ratio for pure, Nj-diluted, andCOj-diluted CH4/air flames keeping lOcm/s for all diluted flames, where all data symbols and lines in black color are obtained from the cruciform burner, while the solid lines are real quenching Hnes. Also plotted are previous data obtained from Chomiak and Jarosinski [11] and Bradley [12]. 

To perform structural research on a food stuff into which a colorant is incorporated, special properties of fluorescing molecules are exploited fluorescence efficiency, fluorescence lifetime, fluorescence quenching, radiationless energy (Foerster) transfer, stationary or time-dependent fluorescence polarization and depolarization." Generally, if food colorants fluoresce, they allow very sensitive investigations which in most cases cannot be surpassed by other methods. 

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