A microdevice with integrated liquid junction for facile peptide and protein analysis by capillary electrophoresis/electrospray mass spectrometry

A novel microfabricated device was implemented for facile coupling of capil lary electrophoresis with mass spectrometry (CE/MS), The device was constru cted from glass wafers using standard photolithographic/wet chemical etchin g methods. The design integrated (a) sample inlet ports, (b) the separation channel, (c) a liquid junction, and (d) a guiding channel for the insertio n of the electrospray capillary, which was enclosed in a miniaturized subat mospheric electrospray chamber of an ion trap MS. The replaceable electrosp ray capillary was precisely aligned with the exit of the separation channel by a microfabricated guiding channel. No glue was necessary to seal the el ectrospray capillary. This design allowed simple and fast replacement of ei ther the microdevice or the electrospray capillary. The performance of the device was tested for CE/MS of peptides, proteins, and protein tryptic dige sts. On-line tandem mass spectrometry was used for the structure identifica tion of the protein digest products. High-efficiency/high-resolution separa tions could be obtained on a longer channel (11 cm on-chip) microdevice, an d fast separations (under 50 s) were achieved with a short (4.5 cm on-chip) separation channel. In the experiments, both electrokinetic and pressure i njections were used. The separation efficiency was comparable to that obtai ned from conventional capillary electrophoresis.