A NEW PH SENSOR WITH A PVC MEMBRANE - ANALYTICAL EVALUATION AND MECHANISTIC ASPECTS

PVC membranes based on a new hydrogen-selective neutral carrier hexabu tyl-tri-amidophosphate (HBTAP) are presented. These membranes also inc lude tetrakis(p-chlorophenyl)borate (TCPB) as the cation-exchanger, di octylphthalate as plasticizer, and PVC. The electrodes provide a pH re sponse in the working pH range 0-6. They can be used in HF solutions u p to 0.1 mol/l. The selectivity coefficients of the electrodes, log K( HM) for ion M are: Li+, -5.3; Na+, -5.3; K+, -6.2; NH4+, -4.7; Cu2+, - 5.0. The hydrogen ions in the membrane form the complexes H(HBTAP)2+. The polarization phenomena at the membrane/solution interface were of the diffusional type. The diffusion coefficients of the H(HBTAP)2+ com plexes in the membrane are estimated as D congruent-to 3 X 10(-7) cm2 s-1 and the dissociation degree of the salt H(HBTAP)2TClPB as 0.1-0.5% .