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    火焰原子吸收光谱法测定土壤中金属元素

    FAAS Determination of Metal Elements in Soil

    • 摘要: 土壤样品用硝酸-氢氟酸-高氯酸(5+5+3)混合酸消解后,采用火焰原子吸收光谱法分别测定了试样溶液中铁、锰、铜、锌、铅、镉和镍的含量。因消解过程中加入了氢氟酸,大部分硅生成四氟化硅气体除去,可在此溶液中直接测定其中铁、锰、铜、锌及镍的量。考虑到SiO32-、Ti(Ⅳ)及Al3+对锰测定有负干扰,加入一定量的氯化钙溶液作为释放剂消除其干扰。如试样含铁量较高,须加入硝酸镧溶液作释放剂以克服其对锌测定的干扰。测定铅及镉时须加入碘化钾溶液使之生成碘化物络阴离子后,用4-甲基-2-戊酮作溶剂进行萃取分离,随后在有机相中测定铅与镉的含量。用7种元素的标准溶液制作了各自的标准曲线,所得线性回归方程的相关系数在0.999 2~0.999 6之间。以土壤样品为基体,加入一定量7种元素的标准溶液做回收试验,得到回收率在96.8%~99.9%之间,相对标准偏差(n=6)在0.9%~2.0%之间。

       

      Abstract: The soil sample was digested with a mixed acid of HNO3-HF-HClO4 (5+5+3) and contents of Fe, Mn, Cu, Zn, Pb, Cd and Ni in the sample solution were determined separately by FAAS. Since most of the silicates in the sample were expelled as SiF4↑ during digestion, contents of Fe, Mn, Cu, Zn and Ni could be determined directly in the digested sample solution. Considering the negative interferences of Ti(Ⅳ) and Al3+ present in the sample and definite amount of SiO32- remained, to the determination of Mn, definite amount of CaCl2 solution was added as releasing agent to eliminate the interference. If relatively high content of iron was present in the sample, La(NO3)3 solution should be added to overcome its interference to the determination of Zn. In determination of Pb and Cd, separation by addition of KI solution to form anionic complexes with Pb2+ and Cd2+ and extraction of the complexes with MIBK were adopted and FAAS determination was done directly in the organic phase. Standard curves of the 7 elements were prepared by using the respective standard solutions, and linear regression equations with correlation coefficients from 0.999 2 to 0.999 6 were obtained. Test for recovery was made by standard addition method, values of recovery and RSD′s (n=6)found were in the ranges of 96.8%-99.9% and 0.9%-2.0% respectively.

       

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