柠檬酸样品经硫酸处理及在550℃灼烧灰化,残渣溶于盐酸(5+95)溶液中。用铁氰化钾将溶液中铅(Ⅱ)氧化成铅(Ⅳ),然后再以硼氢化钾为还原剂,盐酸(1+99)溶液为载流,用氢化物发生-原子吸收光谱法测定铅含量。在优化的试验条件下,铅的质量浓度在20μg·L^-1以内与其吸光度呈线性关系,检出限(3σ)为2.6μg·L^-1。用此方法分析了3个柠檬酸样品,测定值的相对标准偏差(n=6)小于5%,加标回收率在90.5%~110.0%之间。
The sample of citric acid was treated with con.H2SO4,and ashed by ignition at 550℃.The residue was taken up with HCl(5+95)and the species of Pb(Ⅱ)in the solution was oxidized to Pb(Ⅳ)by potassium ferricyanide,and then determined by hydride generation-atomic absorption spectrometry(HG-AAS)with KBH_4 as reducing reagent and HCl(1+99)solution as carrying solution.Linear relationship between values of absorbance and mass concentration of lead was obtained in the range within 20μg·L^-1,with detection limit(3σ)of 2.6μg·L^-1.Three samples of citric acid were analyzed by the proposed method,values of recovery found by standard addition method were in the range of 90.5%-110.0%,with RSD's(n=6)less than 5%.