电感耦合等离子体质谱(ICP-MS)法测定土壤中的碘

Determination of Iodine in Soil by Inductively Coupled Plasma Mass Spectrometry

测定碘在特定样品中的存在形态及含量,是准确评价碘对环境和生态体系影响的关键性因素。土壤生态系统作为全球陆地生态系统的重要组成部分,是联结有机界和无机界的纽带与载体。为精准快速检测土壤中碘含量,采用艾斯卡试剂熔融、热水提取和阳离子树脂交换对土壤样品进行预处理,用电感耦合等离子体质谱(ICP-MS)法测定土壤中的碘含量。通过在样品空白溶液中加入不同用量的阳离子交换树脂进行Na^(+)和Zn^(2+)等阳离子的盐效应消除实验。研究了不同浓度的乙醇介质对碘计数响应的增强效应,选取了不同浓度的氨水介质进行碘记忆效应实验。结果表明,在5 mL样品溶液中加入5 g阳离子交换树脂,基本可以消除Na^(+)和Zn^(2+)的干扰;碘在0.5%、1%和2%的乙醇溶液介质中的计数响应依次递增约达15%,碘在1%、3%和5%氨水介质中的计数响应依次消减约达13.5%。因此,选用3%氨水作为载流,并视仪器灵敏度情况选择样品溶液中乙醇或氨水的介质浓度。方法线性范围宽、检出限低、灵敏度高,可以满足监测分析要求。对国家有证标准物质进行测试,结果均合格,精密度和准确度良好。选取研究区域内若干非污染土壤监测点位进行分层采样、样品制备、预处理和测试,碘平均含量为2.7μg/g,在全国范围内处于中等含量水平;其中,B层平均碘含量为(3.2±2.7)μg/g,略高于A层和C层平均碘含量[分别为(2.5±1.9)μg/g和(2.3±1.6)μg/g]。为今后进一步开展土壤中碘的含量分布、迁移和转化及健康风险评估研究提供了有效的技术支撑。

The determination of the form and content of iodine in specific samples is a key factor to accurately evaluate the impact of iodine on environment and ecosystem.Soil ecosystem,as an important part of global terrestrial ecosystem,is the link and carrier connecting organic and inorganic worlds.To accurately and quickly measure the iodine content in soil,an analytical method was established in this study by the inductively coupled plasma mass spectrometry(ICP-MS)with Eschka reagent melting,hot water extraction,cation resin exchange,and other preprocessing steps.The eliminating experiment of salt effect of cations such as Na^(+) and Zn^(2+) was conducted by adding different amounts of cation exchange resins into the sample blank solution.The enhancement effect of iodine counting response in ethanol medium with different concentrations was studied,and the iodine memory effect test of iodine counting response in ammonia medium with different concentrations was selected.The results showed that adding 5 g of cation exchange resin into 5 mL of sample solution could basically eliminate the interference of Na^(+) and Zn^(2+).As the concentration of ethanol medium increased respectively for 0.5%,1%and 2%,the iodine counting response gradually increased by about 15%.In the contrary,the iodine counting response decreased by approximately 13.5%as the concentration of ammonia media increased respectively for 1%,3%,and 5%.Therefore,it was recommended to select 3%ammonia medium as the carrier cream,and depending on the sensitivity of the instrument,the appropriate medium concentration of ethanol or ammonia in the sample solution was selected.This method had a wide linear range,low detection limit,and high sensitivity,which could meet the monitoring and analysis requirements.The national certified reference materials were tested and the results were all qualified,with good precision and accuracy.Many soil monitoring sites without pollution in the study area were selected,for stratified sampling,sample preparation,pretreatment,and testing.The average iodine content was 2.7μg/g,at a medium level in China.The average iodine content of layer B is(3.2±2.7)μg/g,slightly higher than that of layer A[(2.5±1.9)μg/g]and layer C[(2.3±1.6)μg/g].This study will provide effective technical support for further research on the distribution,migration,and transformation of iodine in soil,as well as the risk assessment for health in the future.