A Microfluidic SPLITT Device for Fractionating Low-Molecular Weight Samples

Abstract

In this article, we report the design of a microfluidic split flow thin cell (SPLITT) fractionation device with internal electrodes placed across the width of its analysis channel for assaying low-molecular weight samples. The reported device allows the realization of lateral electric fields and separation distances of the orders of 100 V/cm and 500 μm, respectively, that are suitable for fractionating such mixtures with high resolution. Our experiments show that a key challenge to realizing electrophoretic fractionations using the current design is to minimize the electroosmotically driven fluid circulations in its SPLITT channel that tend to hydrodynamically mix the liquid streams flowing through this duct. The present work addresses this challenge by chemically modifying the surface of our fluidic conduits with a new coating medium, N-(2-triethoxysilylpropyl) formamide, which has been shown to diminish electroosmotic flow in glass microchannels by over 5 orders of magnitude. Finally, we describe the integration of the reported microfluidic fractionation device to a mass spectrometer via the electrospray ionization interface to allow inline label-free detection of analytes in our assay. Product purity greater than 95% has been accomplished using the SPLITT system presented here for a sample of peptides having the same electrical polarity.