环境样品的热解-溶液吸收预处理及其汞同位素组成的测定

利用多道接收电感耦合等离子体质谱仪(MC-ICP-MS)可实现汞同位素的高精度测定,但对样品预处理的要求很高。目前,液态、固态、气态环境样品的预处理方式不一,存在一定的系统误差。该研究旨在尽可能统一各状态样品的预处理步骤。先将各样品中的不同形态汞富集转化为固体可吸附态,令其吸附在固态载体上,包括:采用金柱富集气体样品中的气态单质汞;以吹扫-金柱捕集法富集液体样品中的溶解气态汞和总汞;用膜过滤法收集大气中的颗粒态汞。最后以管式炉热解定量固态样品,采用高氧化效率的酸性高锰酸钾混合溶液吸收热解产生的Hg~0并氧化为Hg~(2+),保存于溶液中供MC-ICP-MS测定。优化了气体流速、吸收液体积及高锰酸钾浓度等参数,考察了方法空白、回收率及精密度等指标,并将建立的方法应用于大气气态单质汞、大气颗粒态汞、溶解气态汞、雨水总汞和土壤总汞等样品中汞同位素的分析。

A Combustion-Trapping Pretreatment Technique for Environmental Samples and Its Application in Mercury Isotopic Analysis

High-precision determination of mercury isotope ratios using multi-collector inductively coupled plasma mass spectrometry(MC-ICP-MS) requires high quality of sample pretreatment.Different kinds of pretreatment methods developed for liquid,solid and gaseous samples may result in certain systematic errors.This study aimed at unifying the pretreatment techniques of different kinds of environmental samples.Mercury in samples was enriched and transformed into absorbable solid state and then adsorbed onto a solid carrier,including gaseous elemental mercury in gaseous samples enriched with gold column,dissolved gaseous mercury and total mercury in liquid samples enriched with purge and trap method and particulate mercury in the atmosphere collected with membrane filter method.Solid sample was combusted in a tube furnace.An acidic absorbing solution with potassium permanganate was adopted to absorb Hg2+that was oxidized from Hg0 produced in the combustion.Finally,the absorbing solution was analyzed by MC-ICP-MS.The parameters,including oxygen gas flow rate,volume of absorbing solution and concentration of potassium permanganate,were optimized.Method blank,recovery and precision of the method were investigated.The established method was applied in the sample pretreatments of gaseous elemental mercury and particulate mercury in the atmosphere,dissolved gaseous mercury in seawater,total mercury in rain and soil.The isotopic compositions of mercury in the samples were analyzed and discussed.