Microdetermination of fluorine in some inorganic and organic compounds using the fluoride ion-selective electrode

Abstract

The response of the fluoride ion-selective electrode in different aqueous-organic solvents is described. Aqueous dioxan (50% v/v) is the best background for fluoride determination by both direct and potentiometric procedures. Inorganic fluorides are satisfactorily determined by potentiometric titration at pH 5–7 with thorium nitrate solution. Organically bound fluorine compounds are similarly determined after closed flask combustion. Simultaneous determination of chloride and fluoride is also described. Reproducible and accurate results are obtained, the mean absolute error being ±0.3 %. A solid state fluoride ion-selective electrode is constructed using LaF3 doped with SrF2. It gives results favorably compared with the Orion electrode.