Conventional capillary electrophoresis (CE) provides a highly efficient method for analyzing samples in nanoliter volumes. Spectrophotometric detection methods for CE are commercially available, but capillary electrophoresis with electrochemical detection (CEEC), not commercially available, allows analysis of multiple analytes without the use of chromophore dyes. By not requiring a derivatization step, electrochemical detection also provides close to real-time analysis. Earlier methods of CEEC utilized a fragile decoupling joint to isolate the separation voltage from the detection electrodes. These electrodes were often manually aligned in systems that proved challenging to duplicate. In this work, we describe a novel system for CEEC that is both robust and reproducible. A capillary, a palladium decoupler, and a detection electrode were suspended in a fixed configuration in a commercially available epoxy. A poly(dimethylsiloxane) (PDMS) microchannel was used to interface the capillary, decoupler, and detection electrode. As a replacement for the porous decoupling joint, palladium provides an ideal decoupler by absorbing hydrogen gas and allowing for in-channel detection. The transfer of sample from the capillary into the PDMS microchannel resulted in band broadening, but the transfer efficiency was improved by optimizing the PDMS microchannel dimensions to more closely match those of the capillary. Separations of catecholamines, including dopamine, norepinephrine, epinephrine, and catechol, typically yielded 50,000-120,000 theoretical plates for each analyte. By increasing the field strength across the capillary, separation efficiencies were increased with decreased retention times. Finally, decreasing the palladium decoupler size further increased the separation efficiency. The limit of detection for this system was found to be 750 nM. Studies comparing the upper limits of field strengths for the system using different decoupler sizes will also be discussed.

Integrating conventional capillary electrophoresis with electrochemical detection by encapsulating capillary and electrodes in epoxy

246th National Meeting (2013)

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