A glance into the bulk of solvent polymeric pH membranes

The pH-sensitive chromsionsphores brought the dream of the ion-selective me mbrane scientist close to realization. With the help of these molecules, on e can build pH-sensitive, ion-selective electrodes and look into the bulk o f solvent polymeric membranes during potentiometric measurements (spectropo tentiometry) and image concentration profiles in situ with high spatial and temporal resolution. The combination of electrochemical and optical inform ation helped to interpret non-idealities in the potentiometric responses, s uppress or tailor the undesirable transport across sensor membranes, and es timate the residual lifetime of chronically implanted sensors. These novel opportunities provide feedback in membrane optimizations and are expected t o lead to sensor systems with picomolar detection limits and superb selecti vities.