IONOMETRIC DETERMINATION OF FLUORIDE IONS IN WATER AND SOLUTIONS OF TABLE SALT USING ULTRASOUND

The use of ultrasound in the ionometric determination of fluoride ions in water and kitchen salt solutions with the use of preliminary ultrasound treatment of the solution was studied. Experimentally established optimal parameters of ultrasound - frequency 18-44 kHz, intensity ≥ 10 W/cm2 for a time ≥ 1 min. It is shown that pretreatment of the solution with ultrasound of the parameters found leads not only to the cleaning of the electrode from films of organic substances, but also to an increase in the magnitude of the analytical fluoride ions signal, an expansion of the linear region of the calibration graph from 10–5 to 3.5·10–7 M, a reduction response time of the electrode in solutions containing 10-5 M fluorine ions from 10-12 min to 2-3 min. It is shown that the found experimental facts can be explained by structural changes of solutions under the influence of ultrasound. A technique for determining the content of fluoride ions in common salt solutions and water has been developed. The detection limit of fluoride ions in water was 0.007 mg/l, in table salt – 1.2·10–5%.