基于碱溶液提取法的地块土壤中铬(Ⅵ)测定方法的优化  

Method optimization for determination of chromium(Ⅵ)in site soil based on alkali solution extraction

作　　者：李静 丁冬梅 LI Jing;DING Dongmei(Tianjin Eco-Environmental Monitoring Center,Tianjin 300191,China)

机构地区：[1]天津市生态环境监测中心,天津300191

出　　处：《冶金分析》2024年第12期60-65,共6页Metallurgical Analysis

摘　　要：准确测定地块土壤中铬(Ⅵ)含量对污染地块治理和修复具有重要意义。碱溶液提取-火焰原子吸收光谱法是地块土壤中铬(Ⅵ)测定的主要分析方法之一。文章以地块土壤标准物质和实际样品为研究对象,依次考察了加热方式、搅拌速度、液固比、还原性修复药剂对铬(Ⅵ)测定的影响。结果表明:采用水浴加热方式,地块土壤中的铬(Ⅵ)提取更完全,且测定结果的稳定性优于电加热方式;搅拌速度显著影响铬(Ⅵ)测定结果,持续稳定的中速搅拌效果最佳;通常情况下,液固比为10∶1虽然可以满足常规土壤样品中铬(Ⅵ)的有效提取,然而对于铬(Ⅵ)含量超过校准曲线线性范围上限的地块土壤样品,宜通过减少称样量的方式来确定最佳液固比,以确保结果的准确性和可靠性;还原性修复药剂对铬(Ⅵ)加标试验会形成负干扰,在提取前加入过氧化氢,于室温下超声反应5min,能够在改变样品基体还原特性的同时维持土壤样品中铬(Ⅲ)化学形态的稳定性,使铬(Ⅵ)加标回收率提高至75.0%~97.5%,有效消除还原性修复药剂对铬(Ⅵ)基体加标回收试验的干扰。It is of great significance to determine chromium(Ⅵ)accurately in site soil for the management and remediation of contaminated site.Alkali solution extraction-flame atomic absorption spectrometry is one of the main analysis methods for determination of chromium(Ⅵ)in site soil.The certified reference materials and actual samples of site soil were used as research object,and the effects of heating method,stirring speed,liquid-solid ratio and reducing remediation reagent on the determination of chromium(Ⅵ)were investigated.The results showed that the extraction of chromium(Ⅵ)in site soil was more complete when the water bath heating was used,and the stability of determination results were better than that of electrical heating.The stirring rate could significantly affect the determination results of chromium(Ⅵ),and the continuous and steady medium speed stirring showed best effect.Under normal conditions,the liquid-solid ratio of 10∶1could satisfy the effective extraction of chromium(Ⅵ)in conventional soil samples.However,for the site soil samples with chromium(Ⅵ)content exceeding the upper limit of linear range of calibration curve,the optimal liquid-solid ratio should be obtained by reducing sample mass to ensure the accuracy and reliability of determination results.The reducing remediation reagent had negative interference with the standard addition tests of chromium(Ⅵ).Hydrogen peroxide was added before extraction followed by ultrasonic reaction at room temperature for 5min.It could change the reducing properties of sample matrix,and meanwhile,keep the chemical form stability of chromium(Ⅵ)in soil sample.The spiked recoveries of chromium(Ⅵ)increased to 75.0%-97.5%.Therefore,the interference of reducing remediation reagent with the spiked recovery test of chromium(Ⅵ)could be effectively eliminated.

关 键 词：铬(Ⅵ) 碱溶液提取 土壤 污染地块 

分 类 号：O657.31[理学—分析化学] X502[理学—化学]