[A comparative study of determining fluoride ions with spectrophotometric and ion selective methods]

The usefulness of two methods for fluorine determination in different mineral waters was compared: a spectrophotometric method using of a zirconium-xylene reagent and electrochemical using of fluoride ion-sensitive microcapillary inset electrode. The influence of the presence of chlorine, sulphate or iron ions on the fluorine determination has been evaluated in solutions containing 0.5; 1.5; 5.0 and 10.0 mg F-/1 and increasing concentration of Cl-, SO4(2-), Fe3+ ions in the range they can occur in natural mineral waters. The ion-selective method has been found more advantageous for analysis of solutions and waters of mineralization of 5 g/l and concentrations of sulphates below 1,000 mg/l in which fluorides concentrations ranges from 0 to 1.5 mg/l. For solution of higher mineralization degree containing more than 1.5 mg F-/1 and less than 1000 mg/l of sulphates, the spectrophotometric method seems to be more advantageous.