Courtesy ESA Inc.

Figure 60. The Coulometric Electrode System Employing Porous Graphitic Carbon Electrodes

Each electrode unit has a central porous carbon electrode, on either side of which is situated a reference electrode and a auxiliary electrode. As the pressure drop across the porous electrode is relatively small, these electrode units can be connected in series forming an array. Up to 16 units can be placed in series and these arrays are commercially available. However, a sensor system that contains as many as 80 electrodes in the space of a few millimeters has also been constructed (53). A progressively greater potential is applied sequentially to the electrodes of each consecutive unit. This results in all the solutes migrating through the array until each reaches the unit that has the required potential to permit its oxidation or reduction.

 

Courtesy of the Analyst.

Figure 61 Three Dimensional Graphs Demonstrating the Difference between Amperometric and Coulometric Detection Employing an Electrode Array