Journal of Electroanalytical Chemistry, Vol.433, No.1-2, 207-211, 1997
Design of Liquid-Vertical-Bar-Liquid Electrochemical-Cells
Electrochemical cell designs for liquidliquid studies have been briefly summarised. Experiments using reference Luggin capillaries mounted on ball and socket joints showed that the lateral separation between the Luggin tips on either side of the liquidliquid interface had a negligible effect upon the solution resistance. However, the vertical separation, especially of the Luggin tip on the organic side, did have a significant effect upon the uncompensated solution resistance. Even small amounts of uncompensated solution resistance will lead to significant peak separations which might be mistaken for kinetic limitations. Correct compensation of the solution resistance is essential for liquidliquid systems. In many cell designs for liquidliquid systems, the counter electrode for the organic phase is actually in an aqueous solution which is connected to the organic phase by a porous glass frit. The electrical connection between the two phases then relies upon the transfer of a common ion. If the size of the glass frit is too small, the transfer of the common ion can be limited and this in turn will lead to current limitations in the overall cell currents. This results in a characteristic ’clipping’ of the current in a cyclic voltammogram, which cannot be traced to faults in the electronic instrumentation. To avoid this problem, the frit must be at least twice the size of the interface. A new electrochemical cell design for liquidliquid studies which does not possess a Luggin capillary for the organic phase is reported. This Luggin-less cell will exhibit lower impedances for the reference electrode arm than the more conventional reference arms involving Luggin capillaries.
Keywords:IMMISCIBLE ELECTROLYTE-SOLUTIONS;NITROBENZENE-WATER INTERFACE;ION-TRANSFER;IMPEDANCE;PHASE;CAPACITANCE