液相色谱-原子荧光光谱联用法测定土壤砷铬锑硒元素价态

Determination of Valences of As,Cr,Sb and Se in Soil Using HPLC-HG-AFS

土壤重金属污染物的环境效应与其无机价态有密切的关系。As、Cr、Sb和Se元素的价态测定意义重大,但由于价态之间易发生转化使测定工作存在较大难度,标准化程度较低。地质行业标准DD2005-3推荐使用离子交换树脂分离,原子荧光光谱差减法测定As、Sb、Se价态及石墨炉原子吸收光谱法(GFAAS)测定Cr价态。这些方法前处理操作繁琐,测定次数多,工作量大,其他元素形态的存在还会导致结果出现误差。为满足地质调查和评价的需要,本文建立了一套适用于测定土壤水溶态和离子交换态提取液中As、Cr、Sb、Se价态的方法。样品在50℃水浴振荡加热浸提30min,采用液相色谱-原子荧光光谱法(LC-AFS)分离并测定As、Sb、Se价态,一次进样元素的两种无机价态按顺序出峰,同时测定,简便易行,结果更可靠。为了避免了某些离子交换提取剂的屏蔽和干扰,作为补充建立了AFS选择性测定Sb、Se价态的方法,设备成本较低。对于Cr价态的测定,建立了阳离子交换树脂分离-电感耦合等离子体质谱(ICP-MS)的方法,比推荐的GFAAS测定法灵敏度高。As、Cr、Sb和Se的检出限≤0.02μg/g,RSD为3.8%~10.7%,加标回收率为91.0%~106.0%。应用色谱方法对采集的土壤样品进行检测,各项指标满足规范DD2005-3质量要求,与非色谱法相比,实现多组分同时测定。同时初步研究表明,土壤中元素价态含量不高,与土壤总量不存在相关性,采用价态含量作为环境风险评估指标更为合适。

BACKGROUND:The environmental effects of heavy metal pollutants in soil are closely related to their inorganic valence.The determination of the valences of As,Cr,Sb and Se elements is of great significance,but due to the easy conversion between the valences,the determination is difficult and the degree of standardization is low.The geological industry standard DD2005-3 recommends the use of ion exchange resin separation,atomic fluorescence spectrometry to determine the valences of As,Sb,and Se,and graphite furnace atomic absorption spectrometry(GFAAS)to determine the valence of Cr.The preparation of these methods is cumbersome,the number of measurements is large,the workload is large,and the existence of other element forms can also cause errors in the results.OBJECTIVES:To establish a set of methods suitable for determining the valences of water-soluble and exchangeable As,Cr,Sb and Se in soil samples.METHODS:The valences of As,Sb and Se were separated and determined by HPLC-HG-AFS after 30 min extraction in a water bath of 50℃.The processes were simpler and more accurate than the recommended subtraction processes by AFS.To avoid the masking action of some extracting agent,the method of selective determination of Sb(Ⅲ),Sb(Ⅴ),Se(Ⅳ)and Se(Ⅵ)by AFS was developed,which has the advantage of low instrument cost.As for Cr(Ⅲ)and Cr(Ⅵ),after separation by ion-exchange resin,they were determined by ICP-MS,which has higher sensitivity than the recommended GFAAS.RESULTS:The detection limits of As(Ⅲ),As(Ⅴ),Cr(Ⅲ),Cr(Ⅵ),Sb(Ⅲ),Sb(Ⅴ),Se(Ⅳ)and Se(Ⅵ)was≤0.02μg/g,with the RSD of 3.8%-10.7%and the recovery of 91.0%-106.0%.These methods were successfully applied to the analysis of geological samples,and all indices met the quality requirements of DD2005-3.CONCLUSIONS:Compared with non-chromatographic methods,newly established methods by HPLC-HG-AFS can determine multiple components simultaneously.At the same time,preliminary studies have shown that the valence content of elements in the soil is not high,and lacks correlation with the total amount of soil.