Abstract
Each colorimetric method of fluoride analysis has the common defect of a low tolerance for interfering substances. For this reason a clean-up for water or biological samples is always necessary. The recently devised fluoride electrode is said to have no such defect. The author checked the interferences of seven metal ions to the electrode and these interferences were minimized by the use of chelating agents such as citrate. Superior reproductability in multiplicate analysis was shown compared to La-Alizarin Complexon, a solvent extraction method which is believed to be the most reliable to date. In the analysis of domestic well water in a fluoride-rich area, the figures using the electrode were always lower than those using the standard method (Zr-SPADNS). Reason for the discrepancy was analysed and the following results were obtained: The high degree of hardness of the water, i.e. the amount of Ca plus Mg ions induced an apparently higher fluoride concentration using the SPADNS method. Therefore this method appeared to be the one of choice for analysis due to it's simplicity as well as reliability.
