【摘要】 建立了测定茶叶中茶单宁质量分数的分光光度测定方法。利用茶单宁具有的还原性,将Fe3+还原为Fe2+,以邻二氮菲为显色剂,在酸性介质中测定茶单宁的质量分数。考察了检测波长、邻二氮菲加入量、Fe³⁺用量、pH等对测定结果的影响。最佳测定条件为:检测波长为510nm,邻二氮菲加入量为5.0mL,抗干扰剂EDTA的加入量为1.0mL,pH为4.4,反应时间为30min。在此条件下其标准曲线在0².0mg/L范围内呈线性关系,回归方程为:A=0.4827C+0.009,线性相关系数R=0.9891,摩尔吸光系数ε510nm=1.1×104 L/（mol·cm）。加标回收率在99.14%¹02.07%之间,RSD为2.71%。该方法操作简便,灵敏度高,费用低廉,可用于茶叶中茶单宁质量分数的分析。更多还原

【Abstract】 A UV Spectrophotometric method for the determination of tea tanninwas established in this paper.The method was based on the fact that Fe3+can be restored by tannin to Fe²⁺,and Fe²⁺canreact with o-phenanthroline to form salmon pink complexin acid medium,by whichthe tea tannin was determined.In order to obtain the optimal determination results,4crucial determination parameters,including detection wavelength、pH、amounts of chromogenic reagent and Fe³⁺concentration,were investigated.Results showed that the optimal values of the above parameters were as follows:detection wavelength 510 nm,o-phenanthroline amount 5.0mL,hydroxylamine hydrochloride amount 2.0mL,EDTA amount 1.0mL,pH 4.4,and Fe³⁺concentration 0.010moL/L.Under such conditions,agood liner relationship between absorbance（A）and tannin concentration（C）in the range 0².0mg/L was observed,which could be expressed as A =0.482 7C+0.009,（r=0.989 1）,recovery rate was 99.14% ¹02.07%,RSD was2.71%.The method is easy to operate,owning good sensitivity,and low cost,which could be applied to the indirect determination tannin in tea.更多还原