Microdetermination of fluoride in water by ion-exchange spectrophotometry

Abstract

A method for the determination of microgram per litre levels of fluoride has been developed, based on ion-exchange spectrophotometry (IES). The fluoride reacts with slightly polymerised zirconium and xylenol orange and the reaction product is sorbed on Dowex 1-X8 resin. The absorbance of the resin phase at 580 and 750 nm is measured directly. The calibration graph is linear in the concentration range 2–20 µg l^–1 and the RSD is 1.8%. The determination limit with 500 ml of sample is 1.1 µg l^–1; the sensitivity can be enhanced by increasing the sample volume. The method has been applied to the determination of fluoride in tap and raw water using 500 ml of sample.