方波溶出伏安法测定山药中微量元素铜和锌

Determination of trace element copper and zinc in yam by square wave stripping voltammetry

目的:建立山药中 Zn、Cu 微量元素的电化学测定方法。方法:在三电极系统中,以 NH_4Cl为底液,银基汞膜电极为工作电极,铂电极为辅助电极,饱和甘汞电极为参比电极,采用方波溶出伏安法进行测定。结果:在 pH 值5.4～5.6的 NH_4Cl 底液中,在0.3935～5.509 μmol·L^(-1)范围内峰电流与铜(Ⅱ)离子浓度呈现良好的线性关系,线性回归方程:i_p(μA)=102.4C(μmol·L^(-1))-1.038,r 为0.9993,检出限为0.06776 μmol·L^(-1);在 pH 值6.0～6.5的 NH_4Cl 底液中,在0.3823～6.881 μmol·L^(-1)范围内峰电流与锌(Ⅱ)离子浓度呈良好的线性关系,回归方程:i_p(μA)=7.731C(μmol·L^(-1))-2.061,r 为0.9996;检出限为0.2753 μmol·L^(-1)。铜和锌测定的相对标准偏差分别是1.3%和2.9%,加标回收率分别为97%～103%和97%～105%。结论:该方法简便、灵敏度高、准确度好、精密度好,能够满足山药中的微量铜和锌的测定要求。

Objective：To establish a electrochemical method for the determination of trace amount of copper and zinc in yam. Method： A three - electrode system was employed with a mercury film electrode on silversupport as the working electrode,a platinum wire as the counterelectrode and a saturated calomel electrode（SCE） as the reference electrode,a solution of NH4Cl as supporting electrolyte solution. Results：The stripping peak currents increased linearly with the concentration of Cu^2＋ and Zn^2＋ in the range of 0. 3935 μmol . L^-1- 5. 509 μmol . L^-1 in the solution of NH4Cl at pH 5.4 -5. 6 and 0. 3823 μmol . L^-1 -6. 881 μmol . L^-1 at pH 6. 0 -6. 5 respectively. The respective linear regression equation was as following ：ip（μA） = 102. 432C（ μmol . L ^-1 ） - 1.038 （r =0. 9993） ,ip （μA） =7. 731C （μmol . L^-1 ） -2. 061 （r =0. 9996）. The detection limits are 0. 06776 μmol . L^-1for Cu^2＋ and 0. 2753 μmol . L^-1 for Zn^2＋ . The relative standard deviations for determination of copper and zinc was 1.31% and 2. 8% ,and the recoveries of copper and zinc was 97% -103% and 97% -105% ,respectively. Conclusions ：the method was simple, sensitive, accurate and reproducible, and suitable for determination of trace elements copper and zinc in yam.