POTENTIOMETRIC FLUORIDE ANALYSIS WITH IMPROVED ANALYTICAL PERFORMANCE

Since the 1960s SINTEF has, in collaboration with the Nordic aluminium smelters, developed methods for sampling and analysis of fluoride. Unlike conventional potentiometric analysis, this methodology involves detection of fluoride in acidic media. At low pH, the electrode kinetics is improved, resulting in faster analysis. By masking of the fluoride leakage from the ion-selective electrode, the sensitivity of the method is improved. Standard addition methodology is applied for improved analytical performance. The acidic media makes it possible to perform a direct analysis of fluoride in biological samples. In this way, fluoride is extraced from the biological matrix by the acid. The high sensitivity requires low sample masses used and thus does not interfere with the fluoride detection at the ion-selective electrode. This is far more efficient than the conventional approach of ashing the sample at elevated temperatures. Acid extraction can also be applied to filter dust samples.