Integration of Microfabricated Devices to Capillary Electrophoresis−Electrospray Mass Spectrometry Using a Low Dead Volume Connection: Application to Rapid Analyses of Proteolytic Digests

Abstract

This report describes the development of a compact and versatile, micromachined chip device enabling the efficient coupling of capillary electrophoresis to electrospray mass spectrometry (CE-ESMS). On-chip separation provides a convenient means of achieving rapid sample cleanup and resolution of multicomponent samples (typically 2-5 min) prior to mass spectral analysis. A low dead volume connection facilitating the coupling of microfabricated devices to CE-ESMS was evaluated using two different interfaces. The first configuration used disposable nanoelectrospray emitters directly coupled to the chip device via this low dead volume junction, thereby providing rapid separation of complex protein digests. The performance of this interface was compared with that of more traditional configurations using a sheath flow CE-ESMS arrangement where a fused-silica capillary of varying length enabled further temporal resolution of the multicomponent samples. The sensitivity and analytical characteristics of these interfaces were investigated in both negative and positive ion modes using standard peptide mixtures. The separation performance for synthetic peptides using a chip coated with amine reagent ranged from 26,000 to 58,000 theoretical plates for a sheath flow CE-ESMS interface comprising a 15-cm CE column. Replicate injections of a dilution series of peptide standards provided detection limits of 45-400 nM without the use of on-line preconcentration devices. The reproducibility of migration time ranged from 0.9 to 1.5% RSD whereas RSDs of 5-10% were observed on peak areas. The application of these devices for the analysis of protein digests was further evaluated using on-line tandem mass spectrometry.

Generation of mass tags by the inherent electrochemistry of electrospray for protein mass spectrometry

“…First, microfabrication robustness and reproducibility make available reliable micro-and nanospray emitters, with automation possibilities [21]. Second, the design flexibility provided by microfabrication allows the integration of different analytical processes on the same microfluidic device prior to delivery to the mass spectrometer, such as sample preparation [22][23][24], analyte separation [25][26][27], proteolytic digestion [9,28], or even integration of the whole process [29].…”

18 Coupling CE and microchip-based devices with mass spectrometry

“…324,383 The main focus was to create stable ESI conditions and reduce background noise. Designs were quite attractive because they did not require any complex setup, since the outlet was simply formed by dicing the chips.…”

Three-Dimensional Electro-Sonic Flow Focusing Ionization Microfluidic Chip for Mass Spectrometry

“…Although this approach is relatively simple, the ionization source encountered liquid spreading problems along the edge of the chip, thus resulting in the formation of a large Taylor cone. Tapered fused-silica capillaries, which served as electrospray tips, were inserted into the end of the channels in the microfluidic chips to overcome this problem [18]. However, the fabrication process of this approach was complicated.…”