| Abstract
| - Microfluidic chip devices are shown to be attractiveplatforms for performing microscale voltammetric analysisand for integrating voltammetric procedures with on-chipchemical reactions and fluid manipulations. Linear-sweep, square-wave, and adsorptive-stripping voltammograms are recorded while electrokinetically “pumping” thesample through the microchannels. The adaptation ofvoltammetric techniques to microfluidic chip operationrequires an assessment of the effect of relevant experimental variables, particularly the high voltage used fordriving the electroosmotic flow, upon the backgroundcurrent, potential window, and size or potential of thevoltammetric signal. The exact potential window of thechip detector is dependent upon the driving voltage.Manipulation of the electroosmotic flow opens the doorto hydrodynamic modulation (stopped-flow) and reversed-flow operations. The modulated analyte velocity permitscompensation of the microchip voltammetric background.Reversal of the driving voltage polarity offers extendedresidence times in the detector compartment. Rapidsquare-wave voltammetry/flow injection operation allowsa detection limit of 2 × 10-12 mol (i.e., 2 pmol) of 2,4,6-trinitrotoluene (TNT) in connection with 47 nL of injectedsample. The ability of integrating chemical reactions withvoltammetric detection is demonstrated for adsorptivestripping measurements of trace nickel using the nickel−dimethylglyoxime model system. The voltammetric response is characterized using catechol, hydrazine, TNT,and nickel as test species. The ability to perform on-chipvoltammertic protocols is advantageous over nanovialvoltammetric operations that lack a liquid-handling capability. Coupling the versatility of microfluidic chips withthe rich information content of voltammetry thus opensan array of future opportunities.
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