Fast determination of total fluoride by direct potentiometry in samples of aluminium fluoride and cryolite

Abstract

A direct potentiometric method for the determination of the total fluoride concentration in aluminium fluoride and cryolite is proposed. TISAB IV [disodium tartrate-tris(hydroxy-methy1)methylamine-hydrochloric acid] buffer is used to complex the aluminium ions and NaOH is added to the standard solutions to keep constant both the ionic strength and the Na+ concentration as well as the pH. No hydroxide ion interference has been detected even though the pH of this solution is 8.57. A sensitivity loss has been recorded as the electrode ages; in spite of this, the potentiometric measurements are free of systematic errors. The response of the Radiometer and Orion fluoride electrodes with the presence of aluminium in the solution has also been studied, and it was noted that addition of aluminium ions to the calibration solutions was necessary when the Orion electrode was used in order to avoid high error levels. The main random error obtained in the whole process is the owing to the reading using the fluoride electrode. A comparison with the Willard-Winter distillation method was also performed.

Determination of Fluoride Using ion-selective Electrodes in the Presence of Aluminum

“…This may have been due to the formation of mixed aluminum-ligand complexes, as was assumed by Corbillon et al 15 Precision test. For solutions containing 1 and 10 mg L -1 of Ftogether with 100 mg L -1 of Al 3+ , 96 and 97%, respectively, were recovered, when the standard amount of solid TISAB was added.…”

“…TISAB-D was used by Corbillon et al, 15 and prepared as follows. Disodium tartrate dihydrate (230 g), Tris (242 g), and 84 mL of hydrochloric acid (37%) were diluted to 1 L with water.…”

“…We also found that tartrate and Tris-based TISAB-IV (disodium tartrate, tris(hydroxymethyl) methylamine (Tris), hydrochloric acid) reduced the interference from aluminum to a greater extent than the other three TISABs. Corbillon et al 15 reported that TISAB-IV could be used at a pH of 8.4 to complex aluminum ions. Although TISAB-IV has been adopted by the ASTM, 4 the practical applications of TISAB-IV are currently limited 16 due to a lack of published data.…”

Reducing Occupational Risks and Greening a Traditional Sample Treatment of Industrial Fluorine Containing-materials by Application of Design of Experiments

“…Different methodologies have been proposed to achieve the extraction of fluorine from the sample and its further quantification. Distillation, pyrohydrolysis and alkaline fusion were the most used for sample treatments, whereas potentiometric, volumetric or spectrophotometric measurements were the most usual methods for fluorine determination [12][13][14][15][16][17][18][19][20] Furthermore, instrumental breakthroughs lead to the implementation of faster, simpler alternatives such as X-ray fluorescence spectroscopy, with good reproducibility results for the direct analysis of fluorine from solid samples without any pretreatment of the sample [21]. However, these methods have not replaced the official methodologies where Willard-Winter distillation is still the selected procedure for the extraction of fluorine in fluorspar, aluminium fluoride and cryolite [22][23][24].…”

P2.1.11 Fluoride sensing by polymeric membranes based on organoboron Lewis acid receptors

“…Originally, fluoride anions were determined by titration with thorium nitrate. Other recently reported methods were based on potentiometry [1], fluorimetry [2] and colorimetry [3]. Direct potentiometric methods, commonly applying the crystalline fluoride-selective electrode, are suitable for continuous monitoring and replace the expensive and time-consuming instrumental methods.…”