Liquid Chromatography in Microfluidic Chips
Hernan V. Fuentes and Adam T. Woolley
from: Lab-on-a-Chip Technology (Vol. 2): Biomolecular Separation and Analysis (Edited by: Keith E. Herold and Avraham Rasooly). Caister Academic Press, U.K. (2009)
In this chapter, we provide a brief review of the "state of the art" of miniaturized devices for liquid chromatography. Instructions are included for the design, manufacture and application of glass microfluidic chips with integrated micropumps and microchannels for pressure-driven separations. Electrolysis-based micropumps with embedded electrodes were connected fluidically to sample or mobile phase reservoirs to effect sample injection and separation. We developed an on-chip pressure-balanced injection method, which allowed picoliter-range samples to be introduced into a microchannel with no dead volume. Microchannel walls were coated, resulting in a reversed-phase microfabricated open tubular column. The system was used to separate three fluorescently labeled amino acids in less than 40 s with good efficiency (3350 theoretical plates). We review recent efforts aimed at developing microfluidic systems for on-chip liquid chromatography and compare the advantages and disadvantages of our approach to those of others. On chip pressure-driven separations hold great potential to revolutionize many assays in which minute sample volumes must be analyzed fast and in parallel. Moreover, microchips with nL/min flow rates are easy to interface with mass spectrometry, eliminating many of the challenges of coupling conventional columns to electrospray sources read more ...