Fluorescent additives

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]. 

Figure S.S Detection of CoA-SH with CPM as fluorescent addition product.

When adrenaline was oxidized in the presence of Cu++ ions, the loss of the native catecholamine fluorescence was again detected, but in this case the initial oxidation products were also fluorescent. Addition of ascorbic acid did not increase the fluorescence. However, addition of ferricyanide ions destroyed the fluorescence, but it could be regenerated by the addition of ascorbic acid. Noradrenaline behaved somewhat differently in that the initial oxidation product had little fluorescence, probably due to the quenching effect of the Cu++ ions, since reduction of the Cu++ ion concentration increased... 

Fluorescence is not useful simply for chemical analysis. For example, a fluorescent additive that sticks to textile fibres is added to laundry soap. This compound absorbs solar radiation in the non-visible part of the spectrum and re-emits at longer wavelengths in the blue spectral region, which makes clothing appear whiter. Another application of fluorescence encountered daily is cathode tube lighting. The internal walls of these tubes are covered with mineral salts (luminophores) that emit in the visible region due to excitation by electrons. 

Derivatives for LC Detection. The lack of a universal detector for LC and the popularity of the UV detector have caused chromatographers to seek derivatization reactions that introduce UV chromophores into sample analytes. In those instances where the derivative also fluoresces, additional sensitivity can be obtained by fluorometric detection. Table 6 contains a list of the most common derivatizing reagents for this purpose. 

The characteristic colors of PTH-amino acids, following ninhydrin spray and the colored spots observed under UV hght on polyamide plates containing fluorescent additives, are very useful in identifying those amino adds that have nearly identical values. 

There is opinion that stabilizing additives should be colorless [10, 76], on the other hand fluorescent additives (optical bleach) are introduced into polymer in order to compensate yellow painting, which appears at PA processing and also to increase luster and whiteness of products. However, there are works in literature in which there is opinion that it is more preferable to use dyes as stabilizers [77-81], especially if it is necessary to get dyed polymers. 

One of the oldest aspects of discussion about the topic under consideration was the possibility of grafting of polysuccinic anhydride sequences into the polypropylene backbone. The condensation reaction occurring between resorcinol and single succinic anhydride groups, previously bonded to the macromolecule, following Scheme 13.1 leads to the conclusion of the nonexistence of such polysuccinic anhydride grafts, as well as to the finding of a new family of fluorescent additives... 

Table 1. Rate constants for the formation of emission from fluorescent additives (in dm ...

A similar situation occurs in the interaction of a-, p-, and y-CD with diphenylphosphate, 33. In HjO, 33 has two emission bands peaking at 286 and 330 nm. The band at 330 nm is assigned to intramolecular excimer fluorescence. Addition of a- and p-CD to the 33 solution increased the monomer and decreased the excimer band the opposite phenomenon... 

Solvent polarity and the local environment have profound effects on the emission spectra of polar fluorophores. These effects are the origin of the Stokes shift, which is one of the earliest observations in fluorescence. Emission spectra are easily measured, and as a result, there are num ous publications on emission spectra of fluoropho-res in different solvents and when bound to proteins, membranes, and nucleic acids. One common use of solvent effects is to determine the polarity of the probe binding site on the macromolecule. This is accomplished by comparison of the emission Spectra and/or quantum yields of the fluorophore when it is bound to the macromolecule and when it is dissolved in solvents of different polarity. However, there are many additional instances where solvent effects are used. Suppose a fluorescent ligand binds to a protein. Binding is usually accompanied by a spectral shift due to the different environment for the bound ligand. Alternatively, the ligand may induce a spectral shift in the intrinsic or extrinsic protein fluorescence. Additionally, fluorophores often display spectral shifts when they bind to membranes. 

Fibrous cellulose powder with fluorescent additive 33, 83... 

I. Methyl p-hydroxy-benzoate II. Propyl p-hydroxy-benzoate 50 + 50% mixtures Silica gel G + 2% fluorescent additive Pentane-acetic acid (88 -f- 12) UV 254 nm Micro-filtration with G 28 and G 4 glass filter rods. Determination byUV... 

The compounds fiuoresee dark blue (pyridoxal-5 -phosphate, yellow [152]) on dry silica gel layers containing fluorescent additive, when illuminated with UV light 3 xg can be detected in 254 nm, 10 (xg in 365 nm. These colours depend somewhat on the layer and can be modified by treatment with ammonia and alkahes [152]. All Bg compounds yield a bluish product after spraying with 2,6-dichloro- or 2,6-dibromoquinone-chloroimide (Rgt. Nos. 66 and 62 respectively) and subsequent treatment with ammonia vapour (limit of detection 0.1 [xg pyridoxal is the weakest, 0.5—1 [xg). Yamada and Saito [152] have found that the colour shades vary somewhat and depend on the carrier. 

The sensitivity of detection is, with the exception of GC, highest with TLC, provided that corrosive reagents can be used on the adsorbents (alumina, silica gel, Meselguhr shortcoming of cellulose and polyamide). The highly useful so-called alkali fiuorescence [28, 129], specific for the -3-ketosteroids, cannot however be carried out on alumina or silica gel but is possible on cellulose or kieselguhr layers. The use of adsorbents with fluorescent additives for non-destractive detection of steroids which adsorb in the TJV, is the TLC-equivalent of UV-photocopying in PC. The limit of detection with the most sensitive aids is about 0.20 [xg/ spot (2.5 cm ) in PC, 0.01 [xg/spot (0.2 cm ) in TLC and 0.0001 (xg (flame ionisation detector) in GC. 

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