A flow injection system is reported for the determination of fluoride based on its
effects on the fluorescence intensity of Al-morin complex at pH 3.0 in ethanol-warn mixture. The effect of important parameters such as excitation and emission
wavelengths, pH, reagents concenkations, flow rate of the carrier stream, sample
injection volume, time of measurepent and interferences are reported. Cation and
anion exchange resins were used to remove interferences and to preconcenttate
fluoride ions prior to measurement. Calibration curve was linear over the range of 5- 20000 ng ml of fluoride. The deteetion limit was 3 ng ml and the relative standard deviation for the determination of 100 ng ml of fluoride was ±38.7'he proposed method was used to determine ffuofide in natural water samples. R&overy was 97.5- 105% for the fluoride added to the water samples. The relative standard deviation for the andysis of these samples was less than 5%.