Novel ion-selective electrode system for the simultaneous determination of fluoride and calcium in acid solution

Abstract

A method is described that utilises two independent electrode systems; a new ultra-sensitive fluoride-glass pH electrode differential cell and a calcium electrode monitor for the direct and simultaneous measurement of both fluoride and calcium in unbuffered acid solution. Fluoride Nernstian response may be extended by at least one decade towards the lower limit of detection, with an appreciable reduction in electrode response time at low concentrations when compared with the conventional use of fluoride electrodes using TISAB-type buffers. The system has been successfully applied as a biopsy technique for the determination of fluoride concentration profiles within the outer 100 µm of human tooth enamel.