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    流动注射-氢化物发生-原子荧光光谱法测定茶叶中硒

    FI-HG-AFS Determination of Selenium in Tea

    • 摘要: 取经烘干且粉碎的茶叶样品0.5 g,用硝酸-高氯酸(4+1)混合酸10 mL置于电热板上加热消解至溶液呈透明,继续蒸发至剩余约2 mL溶液,加入6 mol·L-1盐酸溶液5 mL,加热使硒(Ⅵ)还原至硒(Ⅳ),重复3次,每次加水2 mL,蒸发以驱除溶液中酸,最后用盐酸(4+96)溶液定容为25 mL。将此溶液以盐酸(4+96)溶液作载流引入流动注射分析系统,同时引入10 g·L-1硼氢化钾溶液(溶于5 g·L-1氢氧化钾溶液中)作还原剂。硒的质量浓度在80 μg·L-1以内与其荧光强度值呈线性关系。方法的检出限(3s/k)为0.034 μg·L-1。应用此方法分析了3种茶叶样品,并以此为基体,加入硒标准溶液做回收试验,测得回收率在97.8%~103.0%之间,测定值的相对标准偏差(n=6)均小于1.5%。

       

      Abstract: 0.5g of dried and powdered tea sample was digested with 10 mL of HNO3-HClO4(4+1) mixed acid by heating on an electric hot-plate to obtain a transparent and clear solution, and then fumed to have a residual solution of ca. 2 mL. 5 mL of 6 mol·L-1 HCl were added and heated to reduce Se(Ⅵ) to Se(Ⅳ). Repeated evaporations (thrice) with additions of 2 mL portions of water to expel acid from the solution, and the solution was finally made up to 25.0 mL with HCl(4+96). The solution was introduced into the FI-system with the carrier HCl(4+96) and 10 g·L-1 KBH4 solution (dissolved in 5 g·L-1 KOH solution) was introduced as reductant. Linear relationship between values of fluorescence intensity and mass concentration of Se(Ⅳ) was kept in the range within 80 μg·L-1. Detection limit (3s/k) found was 0.034 μg·L-1. Samples of 3 kinds of tea were analyzed by this method. Recovery was tested by adding standard Se(Ⅳ) solution to the 3 tea samples as matrixes, values of recovery were found in the range from 97.8% to 103.0%, with RSD′s (n=6) less than 1.5%.

       

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