Determination of inorganic fluoride in blood with a fluoride ion-selective electrode

Inorganic fluoride in whole blood, serum, or plasma has been determined with a fluoride ion-selective electrode by adding the 0.5- to 2.0-mL sample to 20 mL of water containing a buffer and fluoride, 25 micrograms/L. The fluoride concentration in the sample is calculated from the resulting cell potential difference recorded after equilibrating for 10 min. This novel method has the advantages of simplicity, accuracy, and high precision, standard deviations for 5 to 7 replicate determinations of fluoride ranging from +/- 1.7 to +/- 2.4 micrograms/L. For whole blood from donors living in an area with fluorinated drinking water, the F- concentration was 20 to 60 micrograms/L.