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分析了ＦｅＣｌ３—Ｋ３Ｆｅ（ＣＮ）６分光光度法测定植物单宁的适用性。结果表明，在ｐＨ＜２．２时的酸性介质中单宁－ＫＦｅ［Ｆｅ（ＣＮ）６］最大吸收峰在６８０～７２０ｎｍ之间，绝大多数情况下吸收峰在６９５ｎｍ处，比色液单宁浓度在０～８０μｇ·ｍｌ－１时未形成沉淀前，遵守朗伯—比耳定律。时间变异系数每分钟±０．０５％，回收率９４．７％～１０５．２％，相对误差１．２％～５．３％。该方法受在酸性条件下能将Ｆｅ３＋还原为Ｆｅ２＋的物质和形成沉淀的物质干扰。测定结果与靛红—高锰酸钾滴淀法相接近。
The applicability of FeCl3-K3Fe (CN) 6 spectrophotometry for the determination of plant tannin was analyzed. The results showed that the maximum absorption peak of tannin-KFe [Fe (CN) 6] in acid medium at pH <2.2 was between 680 and 720 nm, the absorption peak was at 695 nm in most cases, Ningbian - Beer ’s law was obeyed before no precipitation at 0 ~ 80μg · ml-1. The coefficient of variation of time was ± 0.05% per minute, the recovery was 94.7% ~ 105.2% and the relative error was 1.2% ~ 5.3%. This method interferes with substances that reduce Fe3 + to Fe2 + under acidic conditions and substances that precipitate. The results are in agreement with the isatin-potassium permanganate method.