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

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SiO_3^(2-)、Ti(Ⅳ)及Al^(3+)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 2～0.9996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。

The soil sample was digested with a mixed acid of HNO_3-HF-HClO_4（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 SiF_4↑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 Al^（3＋） present in the sample and definite amount of SiO_3^（2-） remained,to the determination of Mn,definite amount of CaCl_2 solution was added as releasing agent to eliminate the interference.If relatively high content of iron was present in the sample,La（NO_3）_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 Pb^（2＋） and Cd^（2＋） 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.