A Simple and Efficient Device for Treatment of Fluoride Samples in Analysis by the Selective Electrode Method.

Abstract

A simple, efficient and economic device for fluoride mass transference is presented in this study. Hexamethyldisiloxane (HMDS) is used to volatilize fluoride and, in addition to 0.05M NaOH, 0.3M citrate/phosphate/1 M KCl, pH 7.8 (buffer A) and 0.5 M citrate pH 5.5 (buffer B) are used as the trapping solution with the aim of an additional gain when concentration is a limiting condition in the use of the selective electrode. Using 0.05M NaOH, the fluoride mass transferred was in the range of 40 - 0.2 μg, and with buffer A the mass transferred was around 0.2 μg, with a total recovery in a few hours. The influence of interfering substances on fluoride volatilization was assessed. Fluoride was transferred from standard solutions in either the absence or presence of interfering substances (ethanol, propyleneglycol, glycerol, sorbitol, artificial saliva), and the respective recoveries were determined. Due to its simplicity and low cost several device units can be assembled allowing simultaneous analysis for rapid and accurate comparison of different samples. This device is useful for eliminating interfering substances, to concentrate samples as a function of the limit of method, and/or to attenuate gradative loss of the electrode sensitivity.

Key Words:

• fluoride
• mass transference
• concentration
• interfering substances