Integration of microfabricated devices to capillary electrophoresis-electrospray mass spectrometry using a low dead volume connection: Application torapid analyses of proteolytic digests

This report describes the development of a compact and versatile, micromach ined chip device enabling the efficient coupling of capillary electrophores is to electrospray mass spectrometry (CE-ESMS). On-chip separation provides a convenient means of achieving rapid sample cleanup and resolution of mul ticomponent samples (typically 2-5 min) prior to mass spectral analysis. A low dead volume connection facilitating the coupling of microfabricated dev ices to CE-ESMS was evaluated using two different interfaces. The first con figuration used disposable nanoelectrospray emitters directly coupled to th e chip device via this low dead volume junction, thereby providing rapid se paration of complex protein digests. The performance of this interface was compared with that of more traditional configurations using a sheath now 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 bot h negative and positive ion modes using standard peptide mixtures. The sepa ration performance for synthetic peptides using a chip coated with amine re agent 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 dilu tion series of peptide standards provided detection limits of 15-400 nM wit hout the use of on-line preconcentration devices. The reproducibility of mi gration time ranged from 0.9 to 1.5% RSD wheras RSDs of 5-10% were observed on peak areas. The application of these devices for the analysis of protei n digests was further evaluated using on-line tandem mass spectrometry.