抑制溴酚蓝褪色动力学光度法测定茶叶中痕量铜

Kinetic Spectrophotometric Determination of Trace Copper in Tea Based on Inhibited Fading of Bromophenol Blue

基于在pH3.5的HAc-NaAc缓冲溶液介质中,在抗坏血酸活化剂的存在下,痕量铜可抑制碘酸钾氧化溴酚蓝的褪色反应,建立抑制动力学光度法测定痕量铜的新方法,研究相关的测定条件和试剂用量,考察其他离子对测定的影响。结果表明:在优化的最佳实验条件下,方法的测定线性范围为0～0.058μg/mL,检出限为9.04×10-10g/mL,样品加标准回收率在94.3%～102.6%之间,相对标准偏差均不大于4.8%。方法简便、快速,灵敏度高。用于茶叶中铜的测定,结果满意。

A new inhibitory kinetic spectrophotometric method for the determination of trace copper in tea was proposed.The method was based on the fact that in HAc-NaAc buffer solution（pH 3.5）,trace amounts of copper can inhibit the oxidative fading of bromophenol blue induced by potassium iodate in the presence of ascorbic acid as an activator.Important experimental conditions were optimized and interference from co-existing ions was investigated.Under optimized conditions,the linear range of the method was 0–0.058 μg/mL,and the limit of detection was 9.04 × 10-10 g/mL.The average recoveries of copper from spiked tea samples were in the range of 94.3%-102.6% with relative standard deviations less than or equal to 4.8%（n = 6）.The method proved to be simple,rapid,sensitive and has been used to determine trace copper in tea leaves with satisfactory results.