Automated electrochemical analysis with combinatorial electrode arrays

Two combinatorial approaches for rapid automated screening of electrochemical activity of modified electrode surfaces are described. One approach enables simultaneous comparison of electrochemical current by fluorescence associated with pH changes that accompany consumption or production of protons at the electrode surface during a redox process. However, this method cannot distinguish small differences in current at differently modified electrodes. A second approach relies on computer-automated, serial measurement of electrochemical current at each electrode of a 64-electrode array immersed in a single electrochemical cell. Unlike the fluorescent screen, the second method is capable of distinguishing small differences in current at differently modified electrodes, as demonstrated here for gold electrode surfaces covered with organosulfur monolayers of different chain lengths. The improved precision of the computer-automated direct electrochemical method enables examination of active zones that have been first identified by less precise parallel fluorescent screening methods. The direct electrochemical measurement method can easily be extended to a variety of electrode materials, including fuel cell electrocatalysts and redox storage materials. A complete description of the methodology, hardware and computer program for automated measurement is provided.