Investigation of sour substances by a set of all-solid-state membrane electrodes

All-solid-state electrodes were tested in contact with sour taste electrolytes. The tested electrodes consist of two types of membranes. The first sub-layer covering directly the glassy carbon disc is an electroactive polymer, poly(3,4-ethylenedioxythiophene), used as ion-to-electron transducer. The influence of thickness of this membrane on electrode response was examined. The second, outer layer of the sensor, is an ion selective lipophilic compound–polymer membrane. The influence of the thickness and mass ratio of lipophilic compound/polyvinyl chloride of this second layer on the sensor response was also examined. It was found that the thickness of the electroactive polymer has no effect on sensitivity and stability of electrodes used. On the contrary, increase of the thickness of lipophilic compound–polymer membrane causes decrease of sensitivity of electrodes to sour substances and improvement of their stability. It was found that all-solid-state electrodes with positively charged and neutral polyvinyl chloride membranes behave similarly in full contradiction to traditional ion selective electrodes with inner solution. The response of all-solid-state electrodes with positively charged membranes to hydrochloric acid is linear independently on mass ratio of lipohilic compound/polyvinyl chloride used. This suggests that they might work for pH determination.