Dansylation prechromatographic

Prechromatographic dansylation has the advantage that chromatography separates excess reagent and also the fluorescent by-products (e g dansyl hydroxide) from the reaction products of the substances to be determined In the case of postchromatographic dansylation the whole of the plate baekground fluoresees blue, so that in situ analysis is made more diflicult... 

Dansylamides 104,106 — 108 Dansylamino acids 73,107,108 Dansylation 72 ff amines (prim, and sec.) 73 amino acids 73 -, phenols 73 prechromatographic 72 ff with dansyl semicadaveride 73, 53... 

In some cases, a prechromatographic in situ derivatization by overspraying the applied samples with reagent solution can be performed. (see also Section 6.4.1 Prechromatographic Derivatization ). Thus, for example, the application zones of Ce to Ci4 fatty acids were reacted with dansyl semipiperazide or dansyl cadaverine before chromatography [33]. The result of this can be seen in the title illustration of Vols. la and lb of the book by Jork et al. [34]. 

Detection may be facilitated by preparation of colored or, more often, fluorescent derivatives prior to spotting and development. Examples include dansylation (reaction with 1-dimethyl aminonaphthalene-5-sulfonyl chloride) of amino acids and formation of 2,5-dinitrophenylhydrazones of amino acids and ketosteroids. Other reactions that have been used include oxidation, reduction, hydrolysis, ha-logenation, enzymatic, nitration, diazotization, esterification, and etherification (Szepesi and Nyiredy, 1996 Kovar and Morlock, 1996). Prechromatographic derivatization sometimes improves separation, stability, and/or quantification of the analytes in addition to providing visualization. 

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