1987 Volume 36 Issue 3 Pages 169-173
An investigation for the determination of micro amounts of fluoride ion in water samples containing large amounts of sodium chloride or other ions was made by adopting the micro diffusion method with hexamethyl-disiloxane (HMDS) and ion chromatography. The proposed procedure is as follows. Five to sixty cubic centimeter of the sample solution is placed into an outer compartment (max volume 100 cm3) of a polyacrylic diffusion dish and 5 cm3 of a trapping solution (0.1 mol dm-3 sodium hydroxide solution) placed into an inner compartment. HMDS-saturated 2.7 mol dm-3 perchloric acid is added into a sample solution and then diffusion dish is covered with the lid. Generated trimethylfluorosilane is absorbed in a trapping solution by standing for overnight at room temperature. Fluoride ion is determined with ion chromatography after the sodium ion in a trapping solution was exchanged by ion exchange resin (HR). Chromatographic conditions are as follows: column; Shodex IC I-524A (100 mm×6 mm i.d.), eluent; 2.5 mniol dm-3 phthalic acid (pH 4.0, adjusted with TRIS), flow rate; 1.5 cm3/min, detection; conductivity, sample size; 0.1 cm3. A micro amounts of fluoride ion was concentrated twelve times by the proposed method. The detection limit was 4μg dm-3 for fluoride ion. The proposed method was applied to the determination of μg dm-3 level contained fluoride ion in seawater, tap water, well water and lake water.
