Influence of silicone grease on spectrophotometric methods for the determination of fluoride

Abstract

Diffusion methods of the separation of fluoride are of very great importance for the determination of fluorine in biological and other materials. They involve liberating fluoride ions by mineral acids and their absorption in trapping solutions of alkali. As diffusion vessels, polyethylene bottles (1, 2), Conway dishes (3, 4), multicell trays (5), polyethylene stoppers (6), special dishes with two square chambers (7), and plastic Petri dishes (S) are used. In most diffusion methods, silicone grease is used to seal diffusion vessels in order to prevent any leakage of fluoride (4, 5, 7, 9,10). Polyethylene bottles and stoppers only need not be sealed; nevertheless, sealing bottles with wax was also recommended (2). Recently, Taves (10) found that fluoride passes into trapping solutions in the form of methylfluorosi lane if silicone grease is used for sealing; the diffusion of hydrogen fluoride was supposed earlier. In the presence of the simpliest silicone, hexamethyldisiloxane, the separation of fluoride is much more rapid. Therefore, a faster diffusion method for the separation of fluoride was proposed (8). Fluoride was liberated by 25% perchloric acid in the presence of a solution of hexa-

Spectrophotometric methods for the determination of fluoride ion usingindole-3-acetic acid interaction with iron(III)

“…7 The areas in which ion-selective electrodes are commonly used are fluoride determination in tea, 8 food, 9,10 protective dentistry materials, 11−13 waters, 14−16 atmosphere, 17 serum, blood, urine, 18,19 and coal. 20,21 Spectroscopic methods are equally applicable in fluoride determinations in various water samples, 22−26 plants, 27 protective dentistry materials, 28 silicone grease, 29 and samples prepared in the laboratory. 30 Ion-selective electrodes have certain advantages such as the ease of applicability and shorter analysis time.…”