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利用茶多酚与柠檬酸铁铵生成深红色络合物进行分光光度法测定茶多酚。结果表明:在pH>10的碱性介质中络合物的最大吸收峰在550nm处,比色液茶多酚浓度在0～200μg/ml范围内遵从朗伯——比耳(Lambert-Beer)定律。考察了氨试剂、柠糠酸铁铵、羧甲基纤维素钠试剂对测定结果的影响,呈色物质的时间稳定性结果表明:茶汤待测液茶多酚浓度为2.4mg/ml时最适测定条件,低粘度羧甲基纤维素钠试剂用量5ml,柠檬酸铁铵试剂0.5ml,氨试剂0.5ml,蒸馏水定容至25ml,回收率98.3％～101.8％。本方法的缺点主要是低粘度羧甲基纤维素钠试剂需大、中型离心机离心,粘度大,如果没有压吸式移液管,移液较困难。
Determination of Tea Polyphenols by Spectrophotometry Using Dark Red Complexes Between Tea Polyphenols and Ferric Ammonium Citrate. The results showed that the maximum absorption peak of the complex in alkaline medium with pH> 10 was at 550 nm and the concentration of color liquid tea polyphenol was in the range of 0 ~ 200 μg / ml. law. The effects of ammonia reagent, ferric ammonium citrate furfural and sodium carboxymethylcellulose on the determination results were investigated. The results of time stability of the coloring materials showed that the optimum concentration of liquid tea polyphenol was 2.4mg / ml Under the conditions, 5ml of low-viscosity sodium carboxymethyl cellulose, 0.5ml of ferric ammonium citrate, 0.5ml of ammonia reagent and 25ml of distilled water were obtained. The recoveries ranged from 98.3% to 101.8%. The disadvantages of this method are mainly that the low viscosity sodium carboxymethyl cellulose reagent needs to be large, the medium size centrifuge is centrifuged and the viscosity is high, and liquid pipetting is more difficult if there is no pressure suction pipette.