Bioanalytical Applications of Microchip Electrophoresis with Electrochemical Detection

Microchip electrophoresis (ME) is a miniaturized separation method that has the ability to perform fast efficient separations of very small volume samples. Electrochemical detection (EC) is well suited as a detection method for ME. Electrodes can be directly integrated into the chip and the potentiostat and associated electronics are easily miniaturized. The combination of ME with EC generates a powerful tool for bioanalysis; one that is particularly useful for the sensitive and selective measurement of redox active compounds in biological samples. Examples include catecholamines, reactive oxygen and nitrogen species, and antioxidants. Detection limits for ME-EC are generally in the micromolar to high nanomolar range. One of the key issues with ME-EC is isolation of the separation voltage and currents generated by the electrophoretic separation from the working electrode and associated electronics used for the EC detection. Several different electrode configurations and alternative detection strategies have been developed to alleviate this problem and improve LODs. Most recently a dual channel approach that uses a bipolar electrode to convert the electrochemical signal into a fluorescent or chemiluminescence response has been developed by our group. A major advantage of ME makes it possible to detect short lived species, analyze submicroliter samples, as well as monitor multiple analytes simultaneously with high temporal resolution The use of ME-EC for the determination of reactive nitrogen and oxygen species (RNOS) in cell lysates will be described, along with methods for the selective detection of nitrotyrosine modified peptides as biomarkers of oxidative stress. Lastly, the combination of microdialysis with ME-EC for near real-time continuous monitoring of catecholamines, and nitric oxide metabolites in awake, freely roaming animals will be described.