Polyamide fluorescence production

Figure 9. Oxidative polyamide fluorescence production over oils. Key O, linoleic acid A, cottonseed oil.

Figure 12. Polyamide fluorescence production in sugar-amine browning. Conditions Water activity 1.0, 80 °C, sugar, 0.02 M and dipped and dried plate. Key O, blank A, glyceraldehyde 0, xylose and , arabinose.

Fluorescence was measured for polyamide reaction products with three types of materials 1) products of oxidation of a dry oil, 2) products of oxidation of microdisperse lecithin, and 3) sugars. 

As the fluorescent products evolved and certain shortcomings of the above products were noted, similar bulk condensation polymerization methods were carried out to make polyesters and polyamides. These are currently the most widely used fluorescent colorants for plastics. The polyesters allow for lower processing temperatures (<400"F) for bright, clean colors while the polyamides allow for higher processing temperatures (>400"F) and greater shear to achieve color development. 

Although the reagent itself is not fluorescent an excess of NBD-chloride can interfere in quantitative analysis. In such cases it should be checked whether prechromatographic derivatization produces better results [3, 4]. The reaction products can then be separated on polyamide layers. 

Bis-substitution of stilbene produces stronger fluorescence and the bis-triazine derivatives of diaminostilbenes have proved to be the most successful brighteners for cellulosics, in particular, and polyamides (60MI11200). The variety of substitution permutations in (90) is almost endless and many primary and secondary homocyclic and heterocyclic amines, thiols and phenols have been used. Synthesis of such compounds is straightforward and utilizes the convenient selectivity to substitution of cyanuric chloride. 4,4 -Diaminostilbene-2,2 -disulfonic acid condenses readily at 0-5 °C with cyanuric chloride, under slightly acidic conditions. In this case cyanuric chloride behaves as a monofunctional acid chloride and, although some by-products are unavoidable, two molecules of cyanuric chloride condense... 

Draw a picture in your notebook of the polyamide thin-layer plate exposed under UV light after each of the two or three solvent developments. These pictures should look similar to Figure E2.7. Three fluorescent areas should be evident after solvent 2 however, better separation is achieved by solvent 3. A blue fluorescent area at the bottom of the plate is dansic acid (DNS-OH), which is a hydrolysis product of dansyl chloride. A blue-green fluorescent spot about one-third to one-half up the plate is dansyl amide (DNS-NH2), which is produced by reaction of dansyl chloride with ammonia. A third spot, which usually fluoresces green, is the dansyl derivative of the NH2-terminus amino acid. Note the positions of the standard dansyl amino acids and compare with the unknown. What is the identity of the NH2-terminal amino acid Are any other fluorescent spots evident on the plate Using polarity or nonpolarity, try to explain the position of each molecule on the thin-layer plate. 

Dansylation is often used for the determination of free and N-terminal amino acids. Dansyl chloride (5-dimethylaminonaphthalene-l-sulfonyl chloride, DNS-C1) reacts with the amino substituent of amino acids to form highly fluorescent derivatives [75,76]. The method is particularly useful for the analysis of trace components due to the high sensitivity of the products. The derivatives are usually separated by TLC on various types of layers. Separations of DNS-amino acids by flat-bed techniques have been reviewed [77]. Separations by column chromatography have been examined on polyamide [78] and Amberlite IRC-SO [79]. Although many variations of the dansylation reaction with amino acids have been reported, the one described below [77] appears to be the most common. 

Polyamide microcrystalline powders form measurable polymer-bound fluorescent reaction products with malonaldehyde from oxidizing lipids and with reducing sugars. The compounds form on the terminal amine groups which appear to exist in zwitterionic fields with carboxylate anions, as revealed by titration with acid, alkali, or benzoquinones. 

Polyamides can, as a rule, be brightened with those products suitable fi protein fibres. They have, however, an affinity for insoluble dispersions ( organic compounds and, because of their hydrophobic nature, it is on derivatives of this type that can be applied to polyesters. Water-insolub fluorescent brightening agents, in the form of dispersions, are based, one example, on compounds derived from (12) which are favoured becau of their comparatively good light-fastness ... 

Weist, J.L., Karel, M. 1992. Development of a fluorescence sensor to monitor lipid oxidation. 1. Fluorescence spectra of chitosan powder and polyamide powder after exposure to volatile lipid oxidation products. J. Agric. Food Chem. 40, 1158-1162. 

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