Buanuam Janya, Tiptanasup Kasipa, Shiowatana Juwadee, Miró Manuel, Harald Hansen Elo
Department of Chemistry, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, Thailand.
J Environ Monit. 2006 Dec;8(12):1248-54. doi: 10.1039/b612721e. Epub 2006 Oct 26.
A continuous-flow system comprising a novel, custom-built extraction module and hyphenated with inductively coupled plasma-mass spectrometric (ICP-MS) detection is proposed for assessing metal mobilities and geochemical associations in soil compartments as based on using the three step BCR (now the Measurements and Testing Programme of the European Commission) sequential extraction scheme. Employing a peristaltic pump as liquid driver, alternate directional flows of the extractants are used to overcome compression of the solid particles within the extraction unit to ensure a steady partitioning flow rate and thus to maintain constant operationally defined extraction conditions. The proposed flow set-up is proven to allow for trouble-free handling of soil samples up to 1 g and flow rates < or =10 mL min(-1). The miniaturized extraction system was coupled to ICP-MS through a flow injection interface in order to discretely introduce appropriate extract volumes to the detector at a given time and with a given dilution factor. The proposed hyphenated method demonstrates excellent performance for on-line monitoring of major and trace elements (Ca, Mn, Fe, Ni, Pb, Zn and Cd) released when applying the various extracting reagents as addressed in the BCR scheme, that is, 0.11 M CH(3)COOH, 0.1 NH(2)OH.HCl and 30% H(2)O(2), even when a well recognized matrix-sensitive detector, such as ICP-MS, is used. As a result of the enhanced temporal resolution of the ongoing extraction, insights into the breaking down of phases and into the kinetics of the metal release are obtained. With the simultaneous multielement detection capability of ICP-MS, the dynamic fractionation system presents itself as an efficient front-end for evaluation of actual elemental association by interelement comparison of metals leached concurrently during the extraction time. Thus, the intimate elemental association between Cd and Zn in contaminated soils could be assessed.
本文提出了一种连续流动系统，该系统包括一个新型的、定制的萃取模块，并与电感耦合等离子体质谱（ICP-MS）检测联用，用于基于三步BCR（现为欧盟委员会的测量与测试计划）连续萃取方案评估土壤各组分中的金属迁移率和地球化学关联。采用蠕动泵作为液体驱动装置，利用萃取剂的交替定向流动来克服萃取单元内固体颗粒的压缩，以确保稳定的分配流速，从而维持恒定的操作定义萃取条件。所提出的流动装置经证明能够无故障地处理高达1 g的土壤样品，流速≤10 mL min⁻¹。小型化萃取系统通过流动注射接口与ICP-MS联用，以便在给定时间以给定稀释因子将适当体积的萃取液离散地引入检测器。所提出的联用方法在在线监测BCR方案中应用各种萃取试剂（即0.11 M CH₃COOH、0.1 N H₂OH·HCl和30% H₂O₂）时释放的主要和微量元素（Ca、Mn、Fe、Ni、Pb、Zn和Cd）方面表现出优异的性能，即使使用如ICP-MS这样公认的对基质敏感的检测器也是如此。由于正在进行的萃取具有更高的时间分辨率，因此可以深入了解相的分解和金属释放的动力学。凭借ICP-MS的同时多元素检测能力，动态分馏系统成为通过在萃取时间内同时浸出的金属的元素间比较来评估实际元素关联的有效前端。因此，可以评估污染土壤中Cd和Zn之间密切的元素关联。
