A silicon microfluidic chip integrating an ordered micropillar array separation column and a nano-electrospray emitter for LC/MS analysis of peptides

This article presents the development and performance of new silicon microfluidic devices, called E-spray chips, integrating both a reversed-phase separation column and a nano-electrospray emitter. The microchips are made according to standard silicon microtechnology procedures including photolithography, deep reactive ion etching and molecular bonding. The separation column is a perfectly ordered 2-dimensional array of squared micropillars, directly etched in the silicon substrate, and the electrospray emitter is a planar nib-like nanotip. Two chemical procedures for the separation column reversed-phase coating were tested: (i) a liquid phase “chip by chip” process with a C18-alkylated silane and (ii) a vapour phase collective process with a C10-perfluorated silane. Analyses of standard tryptic digests of cytochrome c in hydrodynamic pumping mode have demonstrated good quality spray and effective separation performance of these microdevices with a higher retention capacity for C10-perfluorated coating. These new microchips, which can be produced on a very large scale by a mass production process, from microfabrication to chemical treatment, appear to be very promising analytical tools for proteomics research.