an inexpensive method of determination of fluoride

Abstract

An inexpensive spectrophotometric method of determination of fluoride inwater is developed which is based on bleaching action of fluoride ions on thecoloured complex of Fe (III) with salicylic acid to form stable, colourlesshexafluoride complex of iron. The conditions of the method (pH, stabilityand combination ratio) were studied and a standard curve was obtained for0-20 mg F - /L at 525nm. A study was conducted on interference withcomplexing cations that react with fluoride ions and anions that react withFe (III) to give more stable complex than Fe (III)-fluoride complex. Theresults obtained from this method are compared with standard SPADNS-Zirconyl chloride method. The results obtained are in good agreement withSPADNS-Zirconyl chloride method of determination of fluoride. Thecalibration sensitivity of the method is found to be 0.042 μg -1 .Thedetection limit is found to be 1.1μg mL -1 at 98.3% confidence level. Thesandell’s sensitivity of the method is found to be 0.02 μg mL -1 mL cm cm -2 . -1