ION-SELECTIVE ELECTRODES IN PVC MATRIX

The advantages and disadvantages of the PVC matrix of ion-selective el ectrodes are briefly discussed. Some of newly designed ion-selective e lectrodes (ISEs) with PVC membranes are mentioned. Emphasis is laid on what seems to be known about PVC membranes and on some of the problem s which remain unsolved, as yet. The selectivity patterns of neutral c arrier-based membranes and the so-called anion interference with the c ationic response of the membranes are discussed in the frame of a ther modynamical approach. It is shown that this approach, especially takin g into account the possibility for any ion to present in a membrane a number of different species ('multi-species approach') allows to descr ibe in detail the selectivity as well as the anion interference. Among the problems which remain unsolved, three questions are discussed: (i ) whether the diffusion potential contributes significantly to the mem brane potential; (ii) what is the origin of the cation permselectivity of neutral carrier-based membranes, and (iii) what is the role of the PVC in membranes beside its mechanical role.