In-channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat

The combination of microchip electrophoresis with amperometric detection leads to a number of analytical challenges that are associated with isolating the detector from the high voltages used for the separation. While methods such as end‐channel alignment and the use of decouplers have been employed, they have limitations. A less common method has been to utilize an electrically isolated potentiostat. This approach allows placement of the working electrode directly in the separation channel without using a decoupler. This paper explores the use of microchip electrophoresis and electrochemical detection with an electrically isolated potentiostat for the separation and in‐channel detection of several biologically important anions. The separation employed negative polarity voltages and tetradecyltrimethylammonium bromide (as a buffer modifier) for the separation of nitrite (NO 2−), glutathione, ascorbic acid, and tyrosine. A half‐wave potential shift of approximately negative 500 mV was observed for NO 2− and H2O2 standards in the in‐channel configuration compared to end‐channel. Higher separation efficiencies were observed for both NO 2− and H2O2 with the in‐channel detection configuration. The limits of detection were approximately two‐fold lower and the sensitivity was approximately two‐fold higher for in‐channel detection of nitrite when compared to end‐channel. The application of this microfluidic device for the separation and detection of biomarkers related to oxidative stress is described.