Direct Potentiometric Determination of Total Ionic Fluoride in Biological Fluids

Abstract

Abstract We describe a simple method for measuring fluoride concentration in biological fluids, in which the fluoride ion-specific electrode is used, and which is based on the principle of single known addition. Difficulties associated with variations in pH, temperature, ionic strength, complexation, and nonideal electrode response are thus minimized, and accuracy and precision are maximized. The mean recovery of fluoride added to plasma or to urine was 101.5 or 100.5%, respectively. Analytical variation (coefficient of variation) was 8-10% for plasma and 1.5-4% for urine. The method was applied to 26 sera obtained during hospital pre-admission examinations, and gave a mean ionic fluoride concentration of 1.95 µmol/liter (range, 0.84-2.90 µmol/liter), in reasonable agreement with values reported for other procedures that are based on totally different principles.