The removal of ions of the BGE results in a local decrease in ionic strength and creation of an IDZ, which can propagate several hundred microns upstream of the electrode. This cathodic reaction is coupled to an oxidation reaction at anodic driving electrodes located several millimeters away in the device reservoirs ('+' signs, Scheme 1a). This configuration is similar to that reported previously, for ion depletion carried out at a single permselective membrane-coated electrode in 'half-cell' ICP. A key advantage of fICP over ICP by ion permselection is that charge transfer resistance, instead of the ionic resistance of a membrane, dictates the required potential bias and is often lower, allowing a smaller power supply or batteries to be used.