Comparison of Sample Introduction Methods for Continuous Chemical Purification in Two-Dimensional Electro-Fluid-Dynamic Devices

Two-dimensional electro-fluid-dynamic (2-D EFD) devices, in which both electric field and hydrodynamic pressure are used to drive the analyte and fluid migration, enable chemical separation to proceed in two-dimensional channel networks instead of a one-dimensional column and provide better control on the migration and distribution of analyte in complex channel networks. We have reported the use of a 2-D EFD device to continuously purify multiple components from complex samples ( Liu et al. Anal. Chem. 2010 , 82 , 2182 - 2185 and Liu et al. Anal. Chem. 2011 , 83 , 8208 - 8214 ). A continuous solution stream containing a mixture can be separated into different channels, each containing a pure compound. In previous studies, the sample mixture was introduced into the device by applying an electric field, also known as electrokinetic sample introduction. The initial separation junction requires three separate voltages and one pressure source. In this study, we investigated the mass transfer at the separation junction when the hydrodynamic pressure is used to deliver the sample. The initial separation junction has two voltages and two pressure sources. Continuous chemical purification is demonstrated in EFD devices with different geometries, and the comparison of both sample introduction approaches indicates that hydrodynamic sample introduction is superior to electrokinetic sample introduction.