Thiol-ene microfluidic chip for fast on-chip sample clean-up, separation and ESI mass spectrometry of peptides and proteins

Abstract Mass spectrometry (MS) is a key technology for sensitive and high-resolution mass analysis of peptides and proteins. Sample clean-up and chromatographic separation are usually performed prior to MS analysis to limit adduct formation and ionization suppression. Usually, this is carried out with expensive metal HPLC columns in-line of an electrospray ionization source. Microfluidic devices coupled to MS have gained considerable attention, due to the promise of low manufacturing costs, low sample consumption and channels with a high surface area to volume ratio and tailorable functional groups. Here, we describe a thiol-ene microfluidic chip capable of fast chromatographic sample clean-up, concentration, and separation of complex protein and peptide mixtures with direct on-chip electrospray ionization (ESI). On-chip reversed-phase chromatography (RPC) was performed through an in-situ polymerized monolith frit for retaining inexpensive commercially available reversed-phase (RP) spherical particles, while on-chip ESI is achieved through an emitter monolithically implemented by precision micro milling. The on-chip integration of both RPC and ESI emitter allowed for a minimization of dead-volumes and enables very fast sample clean-up, efficient ionization, and mass analysis of peptides and proteins from complex matrices.