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。传统上利用发酵来还原天然靛蓝染料。然而，在最近的时代，化学试剂，如氢亚硫酸钠有时被用于靛蓝染色与天然靛蓝。研究的目的是区分由亚硫酸盐还原法生产的靛蓝染料和发酵法生产的靛蓝染料。由于靛蓝具有很强的还原力，用亚硫酸氢还原靛蓝可产生过还原物质。用高效液相色谱法对商品靛蓝和用亚硫酸氢还原的再氧化靛蓝中的杂质进行了比较。在众多的杂质中，着色剂是比较容易检测的。发现了一种在商业靛蓝中存在但在氧化靛蓝中不存在的着色剂（最大吸收= 600nm）。但该着色剂的检测结果不具有重复性。然后检查除着色剂外的其他杂质。由于这类杂质的种类繁多，而且分离起来很困难，因此对用亚硫酸还原法染出的靛蓝染料和用发酵法染出的靛蓝染料进行区分仍在进行中。

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.