Spectrophotometric determination of micro amounts of fluoride by alizarin complexoneextraction method

Abstract

Optimum conditions for extraction of a conjugate complex alizarin complexone-lanthanum-fluoride by organic solvent containing amine were investigated and a method of determination of micro amount of fluoride has been established.
To a sample solution in a separatory funnel are added with shaking alizarin complexone solution, a buffer solution of pH 4.4, acetone, and lanthanum chloride solution. It is extracted with 10 ml of 5 vol% N, N-diethylaniline solution in iso-amyl alcohol, and absorbance is measured using a 575 mμ filter.
The results of analysis on 5 μg fluoride were: variation coefficient 1.47%, molar extinction coefficient 23, 500, and absorbance of blank solution 0.06 with 10 mm cell. The method has been applied to the determination of micro amount of fluoride in drinking water with satisfactory results. Ions usually present in drinking water did not interfere.