高碘酸钾氧化刚果红和萘酚绿B褪色催化动力学光度法测定茶叶中的微量锰

Catalytic Kinetic Spectrophotometric Determination of Trace Manganese in Tea Based on Oxidative Discoloration of Congo Red and Naphthol Green B by Potassium Periodate

在NH3-NH4Cl缓冲溶液介质中,以氨三乙酸为活化剂,利用微量Mn(Ⅱ)对KIO4氧化刚果红和萘酚绿B的褪色反应具有催化作用,通过测量480nm和720nm波长处催化和非催化体系吸光度的变化,建立了双波长双指示剂催化动力学光度法测定微量Mn(Ⅱ)的新方法。方法的线性范围为2.4～40μg/L,检出限为0.301μg/L。用于茶叶中锰的测定,加标回收率为96.2%～101.4%。

A dual-wavelength and dual-indicator catalytic kinetic spectrophotormetric method is developed for the determination of trace Mn（Ⅱ）.It is based on the catalytic effect of Mn（Ⅱ）on the oxidation of congo red and naphthol green B by potassium periodate in the medium of NH3-NH4Cl buffer solution（pH=10.0）with nitrilotriacetic acid as activator.The changes of absorbance between catalytic and uncatalytic systems were measured at 480nm and 720nm,respectively.The linear range of the method was 2.4-40μg/L and the detection limit was 0.301μg/L.The method has been applied satisfactorily to the determination of Mn（Ⅱ）in tea samples with recovery of 96.2%-101.4%.