Department of Chemistry, Tarbiat Modares University, Tehran, Iran.
J Sep Sci. 2013 Jul;36(14):2330-8. doi: 10.1002/jssc.201300340.
An efficient method based on ultrasound-assisted emulsification microextraction followed by injection-port derivatization GC analysis was developed to determine 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) in natural water samples. In this procedure, 12.5 μL of 1-undecanol was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample of the analytes located inside an ultrasonic water bath. The resulting emulsion was centrifuged, and 1 μL of the separated organic solvent together with 1 μL of the derivatization reagent were injected into a GC equipped with a flame ionization detector. Several factors that influence the derivatization and extraction were optimized. Under the optimal conditions, the LODs were 0.33 and 1.7 μg/L for MCPA and 2,4-D, respectively. Preconcentration factors of 670 and 836 were obtained for MCPA and 2,4-D, respectively. The precision of the proposed method was evaluated in terms of repeatability, which was <5.7% (n = 5). The applicability of the proposed method was evaluated by extraction and determination of chlorophenoxyacetic acids from some natural waters, which indicated that the matrices of natural waters have no significant effect on the extraction and derivatization efficiency of this method.
一种基于超声辅助乳化微萃取（UAEME）并结合进样口衍生化气相色谱分析的高效方法被开发出来，用于测定天然水样中的 2,4-二氯苯氧乙酸（2,4-D）和 4-氯-2-甲基苯氧乙酸（MCPA）。在该方法中，将 12.5 μL 的 1-十一醇缓慢注入一个 12 mL 的家用离心玻璃小瓶中，小瓶中含有位于超声水浴内的待分析物的水溶液。生成的乳状液经离心分离，然后将 1 μL 分离出的有机溶剂和 1 μL 衍生化试剂注入配备火焰离子化检测器的 GC 中。对影响衍生化和萃取的几个因素进行了优化。在最佳条件下，MCPA 和 2,4-D 的检出限（LOD）分别为 0.33 和 1.7 μg/L。MCPA 和 2,4-D 的预浓缩因子分别为 670 和 836。该方法的重复性精密度<5.7%（n=5）。通过从一些天然水中萃取和测定氯苯氧乙酸来评估该方法的适用性，结果表明天然水的基质对该方法的萃取和衍生化效率没有显著影响。
