MECHANISTIC STUDY OF FLUORIDE-ION SENSORS

Fluoride ion sensitive semiconductor sensors were investigated with regard to the influence of pH, the limit of detection obtained and the response time. The results are the same as those obtained for a well-known single crystal electrode. The dissolution rate of LaF3 was determined using the isotope La-140. The OH-/F- exchange reaction and the isotope exchange kinetics of fluoride ions between the solution and the sensor layer were investigated. In the pH range from 4 to 8 it could be concluded that both the limit of detection and the response time are determined by the ion-exchange rate.