Use of microchip electrophoresis and a palladium/mercury amalgam electrode for the separation and detection of thiols

This paper describes the use of microchip electrophoresis, a palladium decoupler, and a downstream mercury/palladium (Hg/Pd) amalgam working electrode to separate and detect a mixture of thiols. While it is known that palladium forms an amalgam with mercury that enables the selective detection of thiols at a low potential, previous reports have used mercury/gold (Hg/Au) amalgam electrodes and there are no reports of using Hg/Pd electrodes for this purpose. The ability to use a Hg/Pd electrode greatly simplifies the fabrication procedure when a Pd decoupler is used to integrate microchip electrophoresis with electrochemical detection. A detailed comparison was made between the use of Hg/Au and Hg/Pd detection electrodes, with the Hg/Pd electrode having a similar performance in terms of voltammetry, sensitivity, and limit of detection. The resulting palladium decoupler and Hg/Pd electrode were used along with a lengthened serpentine channel to result in the separation and detection of a mixture containing homocysteine, cysteine, glutathione, and N-acetylcysteine. Finally, a microchip device that integrates on-chip pumping and injection valves with the Pd decoupler and Hg/Pd electrode was used to separate and detect glutathione from lysed red blood cells.