Mass transport affected by electrostatic barrier in ionized gel layers attached to microelectrode surface

- Preparation of pH- and charge-sensitive gel modified microelectrodes.
- Negatively ionized gel layer eliminates mass transport of anionic species.
- Migrational contribution may overcome electrostatic barrier of charged layers.

Transport of a redox probe to the surface of an electrode modified with a pH-sensitive polymer network was investigated. After becoming appropriately charged the hydrogel film could act as an electrostatic barrier for negatively charged probes. In the example studied, the charge was obtained by dissociating the carboxylic groups in the polymer network. The percentage of dissociation was determined by the pH of the solution. In parallel, the contribution of migration also played an important role in the transport of the probes. Both regular-sized electrodes and microelectrodes were used in the electrochemical experiments.