Oxidative fluorescence-producing applications

TRS Converter To measure hydrogen sulfide and reduced-organic sulfur compounds, the technique used is thermal oxidation, in which sulfur dioxide is produced. Hydrogen sulfide and other reduced-sulfur compounds are measured by using methods applicable to the measurement of sulfur dioxide concentrations. One method is a technique based on ultraviolet fluorescence. 

Important organic applications are to the determination of quinine and the vitamins riboflavin (vitamin B2) and thiamine (vitamin Bj). Riboflavin fluoresces in aqueous solution thiamine must first be oxidised with alkaline hexacyanoferrate(III) solution to thiochrome, which gives a blue fluorescence in butanol solution. Under standard conditions, the net fluorescence of the thiochrome produced by oxidation of the vitamin Bj is directly proportional to its concentration over a given range. The fluorescence can be measured either by reference to a standard quinine solution in a null-point instrument or directly in a spectrofluorimeter.27... 

The above-presented examples clearly shown that application of coreactant does not require the direct electrochemical generation of both oxidized and reduced forms of a given luminophore. This can be a significant advantage because the use of a coreactant can make ECL possible even in solvents with a narrow potential window so that only a reduced or oxidized form of a luminophore can be produced. Additionally, it is still possible to generate ECL by using a coreactant for some fluorescent compounds that shown only a reversible electrochemical reduction or oxidation. Sometime, when the annihilation reaction between the oxidized and the reduced species is not efficient, the use of a coreactant may produce more intense ECL. 

Oxidation of tetramethylorthothiophenophanes with m-CPBA gave a mixture of thiophene 1,1-dioxides 55 and 56 in a ratio depending on the amount of m-CPBA used (Scheme 55) [65], The thiophene 1,1-dioxide 57 could also be easily obtained using this oxidant (Scheme 56) [66], Application of this method produced novel photochromic compounds 58-60, having relatively high fluorescence efficiencies (Scheme 57) [67], as well as the precursors 61-63 for electron-transporting materials (Scheme 58) [68],... 

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