Excitation to fluorescence

Variously colored zones are produced these can frequently be excited to fluorescence by long-wavelength UV light X = 365 nm) [3],... 

At elevated temperatures and possibly under the catalytic influence of the sorbent surface there is probably elimination of functional groups to yield aromatic ring systems that are excited to fluorescence under long-wavelength UV light (X = 365 nm). 

Digitalis glycosides that react well with various chloramine T - trichloroacetic acid or mineral acid reagents are not excited to fluorescence after treatment with chloramine T — sodium hydroxide. 

Variously colored chromatogram zones appear, some before heating, on a colorless background [1] those produced by aromatic o-diamines are excited to fluorescence by long-wavelength UV light (X = 365 run) [2]. 

Evaluation of chromatograms la 133ff Evaluation, peak area or height la 31,33,40 -, optical trains la 30, 39 Evipan la 339,343 Excitation to fluorescence la 10,12,20,37 Explosion resulting from reagent residues la 82,253,261,315,365 Explosives lb 49,244,407-409 Exposure to vapors la 86... 

Fluorescent thermometry involves the use of a fluorescent dye, whose fluorescence intensity is a strong function of temperature, to infer the temperature of a fluid or surface. The dye is dissolved in a fluid of interest, or coated on a surface, and is excited to fluoresce by incident light. The fluoresced light is recorded with a CCD camera, and variations in its intensity are proportional to variations in the local temperature. 

Aromatic hydrocarbons together with other lipophilic compounds are extracted from a known volume of seawater with n-hexane or cyclohexane in which Gelbstoff and humic substances resulting from natural decay of recent biological material are insoluble. This relative insolubility is important, because many of the latter substances can also be excited to fluoresce and would thus interfere with the determination of oil concentrations. After extraction, the sample solution is dried, brought to a known volume and the intensity of its fluorescence is compared with that of a suitable standard solution. 

For these substances a separation on RP plates (Nano SIL Cig-50, Macherey-Nagel) with the solvent methanol/water (6 4) over a distance of 6 cm was possible (47). The detection is done under a UV lamp by excitation to fluorescence. The Revalues were 0.34 and 0.45 for griseofulvin and dechlorogriseofulvin, respectively (see Fig. 6). For quantitative determinations, 250 nl of standards and samples (concentrations from 0.2 to 1.0 mg griseofulvin/ml ethyl acetate) were spotted and the separated spots excited to fluorescence at 295 nm the emission was scanned at 428 nm. 

Figure 6 RP-separation of griseofulvin (1) and dechlorogriseofulvin (2). Nano SlLCi8-50(Macherey-Nagel) Solvent methanol-water (6 4), migration distance 5 cm, spotting volume 250 ml of solutions of 0.2-1,0 mg/ml ethyl acetate each. Excitation to fluorescence at 295 nm, emission 425 nm.

In many instances, visible fluorescence methods are less subject to interference by other polymer additives present in the extractant than are ultraviolet methods. Thus, Uvitex OB has an intense ultraviolet absorption at a wavelength high enough (378 nm) to be outside the region where many interfering substances in the extractant would be excited to fluoresce. Therefore, in some instances visible fluorimetry offers a method of determining an extractant constituent without interference from other constituents when this would not be possible by ultraviolet spectroscopy. 

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