固体直接进样-电热蒸发电感耦合等离子体质谱联用分析土壤中的重金属元素

乔磊; 叶永盛; 李鹰; 付永强; 周建光; 俞晓峰

doi:10.15898/j.cnki.11-2131/td.201907170107

固体直接进样-电热蒸发电感耦合等离子体质谱联用分析土壤中的重金属元素

Determination of Heavy Elements in Soils by Electrothermal Vaporization-Inductively Coupled Plasma-Mass Spectrometry with Direct Solid Injection

摘要

摘要: 为解决高基质土壤样品中痕量重金属元素检测前处理操作繁琐、样品易二次污染或损失等问题，本文建立了采用固体直接进样-电热蒸发-车载电感耦合等离子体质谱定量分析环境现场土壤样品中Cr、Cu、Zn、As、Cd、Hg和Pb元素的分析方法。该方法采用高温电热蒸发石墨炉作为原子化器，样品称量后经梯度升温选择性蒸发，再结合双通道伴热传输石英管、两路氩气在线稀释、ICP-MS瞬时扫描、基体匹配外部校正等策略，有效解决了土壤直接进样过程中传输效率低、基体效应大的问题。在优化的仪器条件下，按照实验方法称取20mg土壤标准物质GBW07401、GBW07406、GBW07407、GBW07430和GBW07456建立外部校正曲线，样品中7种元素的标准曲线线性相关系数≥0.999；并按照实验方法测定了杭州市滨江区两处田间土壤样品中Cr、Cu、Zn、As、Cd、Hg和Pb，相对标准偏差（RSD） < 7%，相对误差 < 5%，检出限为1.2~32.0ng/g，回收率为91.0%~113.0%。该方法是一种有实用价值的现场样品分析技术，适合现场中大批量土壤样品的分析监测。

Abstract:
BACKGROUNDSolid sampling electrothermal vaporization (ETV)-inductively coupled plasma-mass spectrometry (ICP-MS) allows for a quick analysis of elements at ultra-trace levels and it is possible to minimize the time-consuming sample preparation step which may lead to second contamination or loss of samples. However, the simultaneous introduction of analytical elements, matrix components and solvents into the ICP may cause the spectroscopic and non-spectroscopic interferences. Fortunately, the matrix pyrolysis and analyte vaporization are separated temporally, interferences from the matrix can be reduced from temperature programs. Also, the introduction efficiency of the elements can be enhanced by using bypass gas from the outside of the ETV unit.
OBJECTIVESTo establish a rapid, efficient, and green pre-treatment technique and analytical method for accurate determination of heavy metals in large-scale on-site soil samples.
METHODSA high temperature electrothermal evaporating graphite furnace was used as the atomizer. After weighing, the sample was selectively evaporated by gradient heating, combined with two-channel heat transfer quartz tube, two-way argon online dilution, ICP-MS transient scanning, and matrix matching external correction, which effectively solved the problems of low transmission efficiency and a large matrix effect during direct soil sampling.
RESULTSUnder the optimized conditions, 20mg soil standard materials GBW07401, GBW07406, GBW07407, GBW07430 and GBW07456 were weighed to establish an external calibration curve. The linear correlation coefficient of the calibration curve of 7 elements in the sample was ≥ 0.999. The method was used to determine Cr, Cu, Zn, As, Cd, Hg and Pb in two field soil samples from the Binjiang District of Hangzhou City, which yielded a relative standard deviation of < 7%, relative error of < 2.5%, and a detection limit of 1.2-32.0ng/g, with recoveries of 91.0%-113.0%.
CONCLUSIONSThis method is a practical on-site sample analysis technology, suitable for the analysis and monitoring of large-scale soil samples in the field.

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