Barri Thaer, Bergström Staffan, Norberg Jan, Jönsson Jan Ake
Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Anal Chem. 2004 Apr 1;76(7):1928-34. doi: 10.1021/ac035089g.
A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L(-)(1)-1 microg L(-)(1)), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), and low detection limits (2-3 ng L(-)(1)). Acetonitrile had to be added to the samples in order to overcome the influence of PCB adsorption on the repeatability of extraction and enrichment and to minimize the overall memory effect (OME). OME and carryover depended not only on the concentration of the organic solvent added to the sample and that used in the washing procedure but also on whether the extracting card was changed or not. When an optimized washing procedure was applied, the OME was approximately 0.2% at high concentrations (i.e., 1 microg L(-)(1)). When each extraction took place in a new extraction card, no OME was detected. Additionally, no significant adsorption onto glass surfaces or a matrix effect on extraction was noticed. The main features of this methodology are good extraction repeatability, low detection limits at short extraction time, and the unsurpassed characteristic of no detectable OME in the entire system when each sample is processed in a new card. The total consumption of organic (nonchlorinated) solvents is less than 5 mL per sample.
已开发出一种用于测定水样中亲脂性有机化合物的新型快速自动化样品预处理技术，并将其应用于环境河水中多氯联苯（PCBs）的测定。该技术基于微型微孔膜液-液萃取与带电子捕获检测的气相色谱（GC）在线联用。将样品预处理步骤与最终GC分析同时连接起来的系统核心被称为萃取注射器（ESy）。ESy带有一个连接到电气和机械设计装置上的微型膜萃取卡，直接安装在GC进样器上方，用于提取物的全自动进样。开发了一种方法，从1 mL水样（加入40%乙腈后）中萃取10种多氯联苯同系物，萃取时间为10分钟。优化后的方法显示出良好的线性（动态浓度范围为5 ng L⁻¹ - 1 μg L⁻¹）、33 - 40倍的富集因子、可重复的萃取（RSD为2 - 5%，n = 4）以及低检测限（2 - 3 ng L⁻¹）。必须向样品中添加乙腈，以克服多氯联苯吸附对萃取和富集重复性的影响，并将整体记忆效应（OME）降至最低。OME和残留不仅取决于添加到样品中的有机溶剂浓度以及洗涤过程中使用的有机溶剂浓度，还取决于萃取卡是否更换。当采用优化的洗涤程序时，在高浓度（即1 μg L⁻¹）下OME约为0.2%。当每次萃取都在新的萃取卡中进行时，未检测到OME。此外，未观察到在玻璃表面有明显吸附或萃取存在基质效应。该方法的主要特点是萃取重复性好、在短萃取时间内检测限低，以及当每个样品在新卡中处理时整个系统中无可检测的OME这一无与伦比的特性。每个样品的有机（非氯化）溶剂总消耗量小于5 mL。
