Single Drop Microextraction Using Commercial Capillary Electrophoresis Instruments

Single drop microextraction (SDME), a simple and efficient sample preconcentration method for capillary electrophoresis (CE), was performed using two different commercial CE instruments. With a CE instrument providing adjustable forward and backward pressures, a single drop of an aqueous acceptor phase covered with a thin layer of an organic phase was formed at the capillary tip by programming the sample-handling functions of the instrument to perform 3-phase SDME where the organic film is essentially a membrane. Analytes from an acidic donor phase were concentrated into a basic acceptor phase yielding 190-fold enrichment in 10 min. When the donor phase was agitated using a microstirrer, a 2000-fold enrichment was obtained in 10 min. For a less flexible CE instrument, 2-phase SDME was carried out with a large volume pentanol drop held by a Teflon sleeve, yielding 110-fold enrichments in 30 min. We demonstrate a practical and automated SDME-CE technique with accuracy and reproducibility that is easy to practice to attain matrix isolation and high concentration sensitivity.

单滴微萃取（Single drop microextraction, SDME）是一种用于毛细管电泳（capillary electrophoresis, CE）的简便高效样品预富集方法，本研究采用两台不同的商用毛细管电泳仪器开展了相关实验。当使用具备可调节正、负压功能的毛细管电泳仪器时，通过编程调控仪器的样品处理功能，可在毛细管尖端形成一滴覆盖有薄有机相层的水相接收相液滴，以此开展三相单滴微萃取实验——此时有机薄膜本质上可作为一层分离膜。酸性供体相中的分析物可被富集至碱性接收相中，10分钟内即可实现190倍的富集倍率。当采用微型搅拌器对供体相进行搅拌时，仅需10分钟即可获得2000倍的富集倍率。针对灵活性有限的毛细管电泳仪器，本研究采用聚四氟乙烯（Teflon）套管夹持的大体积戊醇（pentanol）液滴开展两相单滴微萃取实验，30分钟内可实现110倍的富集倍率。本研究验证了一种实用且自动化的单滴微萃取-毛细管电泳（SDME-CE）联用技术，该技术具备优异的准确度与重现性，操作简便易行，可实现基质隔离与高浓度灵敏度检测。