ASSAY OF FLUORIDE CONCENTRATION IN BIOLOGICAL SAMPLES

Abstract

Measurement of fluorine concentration is a need in patients under treatment with fluorine containing compounds. Fluoride in plasma and urine is commonly measured in patients under fluorine treatment, and potentiometry is the most convenient methodology. When NaF is used as a medication, fluoride is the predominant chemical species in plasma and urine. However,during treatment with sodium monofluorophosphate (MFP), peptides and proteins with acid-labile fluorine are present in plasma, the electrode being insensitive to them. In bones, compounds may exist with acid-resistant fluorine, which is detected only after incineration. Several techniques have been developed for the measurement of fluoremia, but not all of them produce real values. In plasma, electrode sensitivity is affected by low fluoride concentration and proteins. Potentiometry after distillation of fluoride and acidlabile fluorine produce trustworthy results. Direct potentiometry is applicable to urine because of the more simple chemical system. Expected levels of fluoride in plasma or urine depend on the exposure of population. For non-exposed people, fluoruria below 50 micromoles/day and fluoremia lower than 1 micromole/L are expected values.