两步连续提取法测定植物中重金属的形态

重金属在植物体内的迁移、转化很大程度上取决于它们的化学形态。文章提出了一种简化的两步连续提取法,根据元素在植物体内活动性的大小,将重金属依次分为乙醇提取态、盐酸提取态和残渣态。采用标准物质(茶叶)对连续提取方法的回收率和精密度进行验证。16次重复测定Cu、Pb、Zn、Cd、Fe和Mn六种重金属元素,3种形态含量之和占各元素总量的82%~116%之间,回收率满足形态分析的要求;各形态含量分析的相对标准偏差,除了Zn、Pb和Cd 3种元素的乙醇态和残渣态在32%~57%之间外,其余均小于20%,表明本方法具有较好的精密度,能满足分析要求。利用蔬菜基地采得的10份植物样品(黄瓜的根、茎、叶片和果实)考察了该方法对不同类型植物样分析的实际应用情况。结果表明,对于根、茎、叶和果实不同植物样品,各元素的3种形态之和占总量的84.6%~106%,回收率满足形态分析的要求。

Analysis of Heavy Metal Fractions in Plants by Two Steps Sequential Extraction Procedure

Migration and transformation of heavy metals in plants depend largely on their chemical forms.A simple two-step sequential extraction procedure was proposed to divide heavy metals into ethanol-extractable fraction,hydrochloric acidextractable fraction and the residue according to their activities in plants.The standard material(tea)was tested to validate the recovery and precision of the simplified extraction method.The sum of three fractions of Cu,Pb,Zn,Cd,Fe and Mn accounted for 82% to 116% of total metals with 16 repeating measurements,which showed that the recoveries can meet the requirements of fraction analysis.And for the relative standard deviation of content of each fraction in 16 repeating measurement,except that the ethanol-extractable fraction and residue of Zn,Pb and Cd were between 32% and 57%,the rest were less than 20%,indicating good precisions for fraction analysis.10 pieces of plant samples including cucumber roots,stems,leaves and fruits picked at vegetable production bases were tested by the extraction procedure to test the practicality of the method,and results showed that for the roots,stems,leaves and fruits of different plants samples,the sum of three fractions of the 6 elements accounted for 84.6% to 106% of the total heavy metals,showing a good recovery for fraction analysis.