A Polymeric Microfluidic Chip for CE/MS Determination of Small Molecules

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Abstract
A polymeric microfluidic chip made of Zeonor 1020 was fabricated using conventional embossing techniques to perform capillary electrophoresis for selected ion monitoring and selected reaction monitoring mass spectrometric detection of small molecules. A silicon master was microfabricated using photolithographic and dry etching processes. The microfluidic channel was embossed in the plastic from a silicon master. The embossed chip was thermally bonded with a Zeonor 1020 cover to form an enclosed channel. This channel (60-μm width, 20-μm depth, 2.0- and 3.5-cm length) provided capillary electrophoresis (CE) separation of polar small molecules without surface treatment of the polymer. A microsprayer coupled via a microliquid junction provided direct electrospray mass spectrometric detection of CE-separated components. An electric field of 0.5−2 kV/cm applied between the microsprayer and a separation buffer reservoir produced a separation of carnitine, acylcarnitine, and butylcarnitine with separation efficiencies ranging from 1650 to 18 000 plates. Injection quantities of 0.2 nmol of these compounds produced a separation of the targeted polar small molecules without surface treatment of the polymer−abundant ion current signals and baseline separation of these compounds in less than 10 s. These results suggest the feasibility of polymeric chip-based devices for ion spray CE/MS applications.