Determination of Fluoride in Vegetation: A Comparative Study of Four Sample Preparation Methods
Abstract Four sample preparation methods (dilute acid digestion, concentrated acid digestion, alkali fusion, and low temperature ashing) for the determination of fluoride in vegetation are compared. A fluoride ion selective electrode is used for the final quantitative measurements. Ionic strength and pH are maintained by a concentrated citrate buffer. The highest sensitivity and reproducibility are obtained by low temperature ashing of the dry sample. Several vegetables, grown in the neighborhood of a glaze factory, were simultaneously analyzed by 2 of the methods, the dilute acid digestion and the low temperature ashing procedures. The higher fluoride content found with the latter technique is attributed to the complete mineralization of the sample.