Discrimination between an indigo dyeing produced by the reduction with hydrosulfite and that produced by fermentation

靛蓝在染色前必须在碱性条件下还原。传统上，发酵已被用于还原天然靛蓝染料。然而，在最近的时间，化学试剂，如连二亚硫酸钠有时用于靛蓝染色与天然靛蓝。研究了连二亚硫酸钠还原靛蓝染料与发酵靛蓝染料的区别，由于连二亚硫酸钠还原靛蓝染料的还原能力强，可产生过还原物质。采用HPLC法比较了市售靛蓝和再氧化靛蓝（用亚硫酸氢盐还原）中的杂质。在众多杂质中，着色剂是便于检测的。发现了一种着色剂（最大吸收= 600 nm），该着色剂存在于市售靛蓝中，但不存在于再氧化靛蓝中。然后检查除着色剂外的其他杂质。由于这些杂质的种类繁多，分离困难，所以对用连二亚硫酸盐还原法和发酵法生产的靛蓝染料的鉴别正在进行中。

Indigo must be reduced under alkaline conditions before dyeing. Traditionally fermentation has been utilized for the reduction of natural indigo dye. However, at recent times chemical reagents such as sodium hydrosulfite is sometimes used for indigo dyeing with natural indigo. The purpose of the research is to discriminate an indigo dyeing produced by the reduction with hydrosulfite from that produced by fermentation.Perreduced substances can be produced by the reduction of indigo with hydrosulfite because of its strong reducing power. Impurities in commercial indigo and in reoxidized indigo which is submitted to the reduction with hydrosulfite was compared using HPLC. Among many impurities, colorants are convenient to detect. A colorant (absorption maximum = 600nm) which is present in commercial indigo but is not present in reoxidized indigo was found. However the detection of this colorant was not reproducible. Then other impurities besides colorants were examined. Because of the variety and the badness of separation of such impurities, the discrimination between an indigo dyeing produced by the reduction with hydrosulfite and that produced by fermentation is in progress.