薄層クロマトグラフィーによる色素の分析について (第6報)

キサンテン系色素アルカリ分解物について その1フルオレセインならびにエオシンについて

抄録

The structure of xanthene dyes can be clarified by hydrolyzing the dyes with caustic alkalies and by analyzing products resulted from the hydrolysis. The present paper describes the separation and detection of the hydrolysed products by means of thin layer chromatography.
When fluoresceine is hydrolyzed with 50% sodium hydroxide solution, it yields resorcinol and 2- (2′, 4′-dihydroxybenzoyl) -benzoic acid. The structure of the latter compound has been made clear by the infrared and nuclear magnetic resonance spectra. These two products could be separated on a thin layer of sillica gel, using a solvent system of dioxane+dichloromethane+pyridine (5: 18: 0.8). The location of the spots was achieved by spraying the chromatoplate with a solution of diazotized sulfanilic acid and then by exposing to NH₃ vapour. Resorcinol was revealed as a brownish-yellow colored spot and 2- (2′, 4′-dihydroxybenzoyl) -benzoic acid as a brown colored spot.
In the case of eosine, its hydrolysed products, i. e. 2, 4-dibromoresorcinol and 2- (3′, 5′-dibromo-2′, 4′-dihydroxybenzoyl) -benzoic acid have been confirmed by the infrared and nuclear magnetic resonance spectra. They could be separated on a thin layer of silica gel each of them, using ethyl alcohol+benzene+glacial acetic acid (25: 90: 4) and the location of the two spots was carried out in the same way. Chromatograms are shown in the Figs. 1 and 6.