A polymeric microfluidic chip for CE/MS determination of small molecules

A polymeric microfluidic chip made of Zeonor 1020 was fabricated using conv entional embossing techniques to perform capillary electrophoresis for sele cted ion monitoring and selected reaction monitoring mass spectrometric det ection of small molecules. A silicon master was microfabricated using photo lithographic and dry etching processes. The microfluidic channel was emboss ed in the plastic from a silicon master. The embossed chip was thermally bo nded with a Zeonor 1020 cover to form an enclosed channel. This channel (60 -mum width, 20-mum depth, 2.0- and 3.5-cm length) protided capillary electr ophoresis (CE) separation of polar small molecules without surface treatmen t of the polymer. A microsprayer coupled via a microliquid junction provide d direct electrospray mass spectrometric detection of CE-separated componen ts. An electric field of 0.5-2 kV/cm applied between the microsprayer and a separation buffer reservoir produced a separation of carnitine, acylcarnit ine, and butylcarnitine with separation efficiencies ranging from 1650 to 1 8 000 plates. Injection quantities of 0.2 nmol of these compounds produced a separation of the targeted polar small molecules without surface treatmen t of the polymer-abundant ion current signals and baseline separation of th ese compounds in less than 10 s. These results suggest the feasibility of p olymeric chip-based devices for ion spray CE/MS applications.