Thick-film electrochemical detectors for poly(dimethylsiloxane)-based microchip capillary electrophoresis

A new poly (dimethylsiloxane) (PDMS)-based microchip capillary electrophoresis (CE) device, with a thick-film electrochemical detector, is described. The end-column design relies on screen-printing the amperometric carbon working electrode on the base plate of a PDMS microchip (opposite to the exit of the microchannel). Since the channel depth and electrode height are quite similar, this is a flow-onto/flow-by hybrid arrangement. The influence of relevant experimental variables, such as the separation and detection potentials, is reported along with the attractive analytical performance. Flat baselines and extremely low noise levels are observed even at high separation fields (approaching 700 V/cm), reflecting the effective electrical isolation of the detector. The resulting detection limits (150 nM for epinephrine and 280 nM for catechol) compare favorably with those obtained by other PDMS-based electrochemical detectors. Such coupling of low-cost and versatile PDMS chips and thick-film electrochemical detectors holds great promise for high-volume production of disposable microfluidic analytical devices.