Mobile species uptake by polymer-modified electrodes

The use of mobile species uptake by a polymer-modified electrode as a probe of solution composition is discussed. The over-all mobile species exchange process between the polymer and solution phases is monitored gravimetrically, using the electrochemical quartz-crystal microbalance (EQCM). The influence of electroneutrality and activity constraints is considered under both equilibrium and transient conditions. The generality of detection by mass and the high sensitivity of the EQCM have analytical advantages. Selectivity requires separation of the total mass change into single species' components. The thermodynamic and kinetic approaches to the problem of selectivity are explored.