关键词: 加标浓度直读法, 茶叶, 铜, 溶解特性

Abstract:

A new method to detect copper ions with different dissolution characteristics in tea was established. After
sequential extraction of tea samples with water and alkali, the remaining residue was microwave-digested and detected with
a copper-selective electrode by directly reading the concentrations of copper ions. Results showed that the optimal amounts
of 1.00 mol/L potassium nitrate and 1.00 mol/L sodium fluoride added were both 5.00 mL in total ionic strength adjustment
buffer (TISAB) at pH 4.00. The conversion factor of the copper ion selective electrode was more than 93%, indicating that
the Nernst response of this electrode is quite good. Under these experimental conditions, the relative standard deviation for
11 repeated determinations of tea samples was 2.4%, the spike recoveries were in the range of 94.38%–101.22%, and the
detection limit was 1.20 × 10-6 mol/L. Satisfactory analytical results were obtained by using the method in comparison to the
national standard method.

Key words: concentration direct-reading after standard solution addition, tea, copper, dissolution characteristics