Concentration Of Free Fluoride Ions Research Articles

Evaluation of free and total fluoride concentration in mouthwashes via measurement with ion-selective electrode

BackgroundThe aim of this study was to compare free fluoride concentration and total fluoride concentration in mouthwashes.MethodsFluorine-containing mouthwashes from various companies and manufacturers (Colgate Total Plax Classic Mint®, Colgate-Palmolive, New York, USA; Colgate Total Plax Gentle Mint®, Colgate-Palmolive, New York, USA; Colgate Total Plax Fresh Mint®, Colgate-Palmolive, New York, USA; Oral B Advantage®, Procter&Gamble, Cincinnati, USA; Reach Fresh Mint®, Johnson&Johnson, New Brunswick, USA; Foramen®, Laboratorios Foramen, Guarnizo, Spain; Lacalut Sensitive®, Dr. THEISS, Homburg, Germany; Sensodyne®, GlaxoSmithKline, London, UK; Vesna F®, Vita, Saint Petersburg, Russia; Lacalut Fresh®, Dr. THEISS, Homburg, Germany) were selected as study objects. Fluoride measurements were carried out using the fluoride selective electrode.ResultsFree fluoride:total fluoride ratio was more than 80% for six samples (Colgate Total Plax Gentle Mint® - 88%, Colgate Total Plax Fresh Mint® - 99%, Oral B Advantage® - 92%, Reach Fresh Mint® - 92 and 89% for the mouthwash of another batch, Lacalut Sensitive® - 94%) and less than 63% for three samples (Colgate Total Plax Classic Mint® - 56%, Foramen® - 62%, Vesna F® - 61%). Two samples had more than 70% and less than 80% of unbound fluoride, respectively (Sensodyne® - 77%, another batch of Oral B Advantage® mouthwash - 74%). Rinse containing sodium monofluorophosphate (Na2PO3F) (Vesna F®) had more than 50% of free fluoride, while the rinse containing amine fluoride (AmF) (Lacalut Sensitive®) had 94%. The difference in the free fluoride:total fluoride ratio can be explained by binding of fluoride ions by components contained in mouthwashes, such as coloring agents and polymeric compounds. The lowest concentration of free fluoride ions (0.000093 mol/L) was observed for aluminum fluoride (AlF3) rinse (Lacalut Fresh®), while the total fluoride amount was not determined due to possible generation of strong fluoride complexes. This implies that fluoride ions will not be uptaken by tooth tissue and may even be washed away from it, compromising the efficacy of mouthwashes.ConclusionsThe differences in free fluoride: total fluoride ratio between analyzed mouthwashes reveal a need to develop a method for evaluation of free fluorides in mouthwashes for proper updating of national and international guidelines.

Free fluoride determination in honey by ion-specific electrode potentiometry: Method assessment, validation and application to real unifloral samples

Surprisingly, a reliable method for measuring the concentration of free fluoride ions in honey is still missing from the literature, notwithstanding the generally recognized importance of the analyte and the matrix. To fill this gap, this study proposes and validates a straightforward ion-specific electrode potentiometric method for this task. The method offers very low detection and quantification limits (6.7μgkg−1 and 25μgkg−1, respectively), good linearity (R2>0.994), good sensitivity (typically 55±3mV for an order of magnitude of concentration) in an unusually low concentration interval (between 0.020 and 1mgL−1), and acceptable precision and bias. The method was applied to 30 unifloral (thistle, eucalyptus and strawberry tree) honey samples from Sardinia, Italy. The amount of free fluoride ions found in these honeys appears to be lower than the range usually found in the literature; indeed, early results suggest a possible dependence of the analyte concentration on the honey’s botanical origin.

Oscillations in the Concentration of Fluoride Ions Induced by a pH Oscillator

Sustained oscillations in the concentration of free fluoride ions can be generated when the BrO3--SO32--Mn(II) oscillator is coupled either to Al3+-F- complex formation or to the Ca2+-F- precipitation process in a flow reactor. By careful analysis of the relevant equilibria and optimization of the reactant concentrations, one can obtain [F-] oscillations of several orders of magnitude as measured with an ion-selective electrode. The BrO3--SO32--Mn(II)-Al(NO3)3-NaF system also exhibits bistability, that is, simultaneously stable steady states of high and low [F-].

Effects of Fluoride Dentifrices on Enamel Lesion Formation

An in vitro pH cycling model was used to test the hypothesis that the effects of 3 different fluoride compounds on de/remineralization are a function of the free fluoride ion concentration. Groups of 10 human enamel specimens were treated with one of: (a) amine fluoride (AmF), 1250 ppm F; (b) sodium monofluorophosphate (NaMFP), 1000 ppm F; (c) sodium fluoride (NaF), 1100 ppm F; (d) NaF, 250 ppm F; (e) Placebo (< 1 ppm F) dentifrices; or with aqueous solutions (f) NaF 900 ppm F or (g) NaF 30 ppm F. Lesions were assessed by cross-sectional microhardness. Mean +/- SEM DeltaZ (vol.% x microm) values of 3 dentifrices were: (a) 344 +/- 155, (b) 4259 +/- 257, and (c) 591 +/- 83. The AmF (1250 ppm F) was not statistically significantly different from the NaF (1100 ppm F) dentifrice in this model. The NaMFP (1000 ppm F) dentifrice, without hydrolysis, had only the same efficacy as the NaF (30 ppm F) aqueous solution.

The Influence of Ionic Strength on Yttrium and Rare Earth Element Complexation by Fluoride Ions in NaClO4, NaNO3 and NaCl Solutions at 25 °C

Stability constants of the form F β 1(M)=[MF2+][M3+]−1[F−]−1 (where [MF2+] represents the concentration of a yttrium or a rare earth element (YREE) complex, [M3+] is the free YREE ion concentration, and [F−] is the free fluoride ion concentration) were determined by direct potentiometry in NaNO3 and NaCl solutions. The patterns of log10 F β 1(M) in NaNO3 and NaCl solutions very closely resemble stability constant patterns obtained previously in NaClO4. For a given YREE, stability constants obtained in NaClO4 were similar to, but consistently larger than F β 1(M) values obtained in NaNO3 which, in turn, were larger than formation constants obtained in NaCl. Stability constants for formation of nitrate and chloride complexes ( $_{\mathrm{NO}_{3}}\beta_{1}(\mathrm{M})=[\mathrm{MNO}_{3}^{2+}][\mathrm{M}^{3+}]^{-1}[\mathrm{NO}_{3}^{-}]^{-1}$ and Cl β 1(M)=[MCl2+][M3+]−1[Cl−]−1) derived from F β 1(M) data exhibited ionic strength dependencies generally similar to those of F β 1(M). However, in contrast to the somewhat complex pattern obtained for F β 1(M) across the fifteen member YREE series, no patterns were observed for nitrate and chloride complexation constants: neither $_{\mathrm{NO}_{3}}\beta_{1}(\mathrm{M})$ nor Cl β 1(M) showed discernable variations across the suite of YREEs. Nitrate and chloride formation constants at 25 °C and zero ionic strength were estimated as log10 $_{\mathrm{NO}_{3}}\beta_{1}^{\mathrm{o}}(\mathrm{M})=0.65\pm 0.06$ and log10 Cl β 1 o (M)=0.71±0.05. Although these constants are identical within experimental uncertainty, the distinct ionic strength dependencies of $_{\mathrm{NO}_{3}}\beta_{1}(\mathrm{M})$ and Cl β 1(M) produced larger differences in the two stability constants with increasing ionic strength whereby Cl β 1(M) was uniformly larger than $_{\mathrm{NO}_{3}}\beta_{1}(\mathrm{M})$ .

ENDEMIC FLUOROSIS THROUGH DRINKING WATER AND ITS REMEDIAL MEASURE BY BACTERIAL POPULATION — A MATHEMATICAL MODEL

Fluoride-contaminated drinking water is a serious public health hazard in some parts of India. Field surveys have been conducted in fluoride-affected areas of the Birbhum district, West Bengal, India. From these surveys, it is found that in certain locations the drinking water contains less fluoride (within the permissible limit1) than in adjoining areas. We have isolated a strain of Streptococcus species from these wells that has the ability to remove the fluoride ion from the water. We have grown the bacteria in different concentrations of fluoride and monitored the decline in the free fluoride ion concentration. A simplified model of fluoride and bacterial dynamics is proposed. The model is handled both analytically and numerically. For numerical solution mainly our own laboratory data are used. Calibration and validation are performed with different sets of experimental data. Analytical solutions show that the bacterial consumption and growth rates are the most important parameters in the system. Analysis shows asymptotic stability of the system.

Effects of aluminium(III) and fluoride on the demineralization of bovine enamel powder and hydroxyapatite; in vitro kinetic studies showing synergistic inhibition

The effect of Al(III) and fluoride on the rate of dissolution of powdered enamel in 0.1M lactate solution has been studied at pH 4.5 and 5.0. The dissolution rate of synthetic hydroxyapatite (HAP) microcrystals in similar solutions is reported for pH 5.0. A combination of Al(III) and fluoride has a stronger inhibitory effect on dissolution of enamel and HAP at pH 5.0 than that of these substances separately, even though the concentration of free fluoride ions decreases in the presence of Al(III). The effects on dissolution of enamel at pH 4.5 are similar, but less pronounced. It is suggested that Al(III) and its major complexes in slightly acidic solution, being positively charged, are adsorbed at different sites on the mineral surface from fluoride, thereby producing a synergistic effect. When the dissolution process takes place far from equilibrium, inhibitor concentrations greater than about 100μM ( ∼ 3 ppm for Al(III) and ∼ 2 ppm for F −) show significant inhibition under the conditions studied. In such solutions the real concentration of Al 3+ is of the order 1μM. Close to equilibrium, the total inhibitor concentration need only be of the order 1μM (i.e. 0.03 ppm for Al(III), 0.02 ppm for F −) for a strong effect. In such solutions, the real concentration of Al 3+ is in the nanomolar range.

Determination of Fluoride in Cocoa Powder by Ion‐Selective Electrode

ABSTRACTA method to determine free fluoride concentration in soluble cocoa powder by a fluoride‐selective electrode was developed and validated. Calibration was linear over the 0.51 to 3.03 ppm range. Free fluoride ion concentration data were in the 0.52 to 1.49 ppm range, with recoveries varying from 81% to 89% using a standard addition procedure.

Anion Exchange Separation of Hard Acid-metals Using HF–H3BO3 Media

Abstract The properties of HF–H3BO3 media and the distribution coefficients of eighteen metals have been investigated to achieve the separation of hard acid-metals by the anion exchange method. As the addition of boric acid to hydrofluoric acid solution reduces the free fluoride ion concentration to about one hundredth, it is possible to control the formation of metal fluoride complexes in a way favorable for the separation. The BF4− and BF3OH− produced in this media are adsorbed strongly to the resin and reduce the relative adsorbabilities of metal fluoride complexes remarkably. Using these properties of HF–H3BO3 media and the adsorbabilities of other anions, a new anion exchange method for the separation of hard acid-metals has been proposed. The new method is especially useful for the separation of titanium, zirconium, niobium, and tantalum. Distribution coefficients and elution behaviors of metal ions are not affected by the increase of the amount of metals because of the buffer action relating to the fluoride in HF–H3BO3 media.

Cation Exchange Separation of Metal Ions Using HF–H3BO3 Media

Abstract Using hydrofluoric–boric acid media, a new cation exchange method for the mutual separation of metals which form stable fluoride complexes has been developed. The addition of boric acid to a hydrofluoric acid solution reduces the free fluoride ion concentration to about one hundredth because of the formation of fluoroboric acid. This reduction of the free fluoride ion concentration makes it easy to control the formation of metal fluoride complexes, favoring their separation. As the fluoroboric acid has a buffer action relating to the fluoride ion concentration, the distribution coefficients of metal ions are not affected by the increase in the concentrations of metal ions, even at a low concentration of fluoride ions in the solution. By the use of hydrofluoric–boric acid media, such metals as zirconium, titanium, aluminium, and uranium can be separated from each other. The distribution coefficients of eighteen metals were investigated both in hydrofluoric acid and hydrofluoric–boric acid solutions.

Thermodynamic parameters of thorium-fluoride complexes from measurements with the fluoride-selective electrode at 5, 25, and 45°C

Stability quotients for the thorium-fluoride and hydrogen-fluoride systems in 0·01 M NH 4NO 3 at 5, 25, and 45°C were determined from measurements of free fluoride ion concentration by the lanthanum fluoride membrane electrode. Thermodynamic stability constants, standard enthalpies, and standard entropies were derived from the experimental data for formation of ThF 3+, ThF 2 2+, ThF 3 +, ThF 4, and HF.

Determination of stability constants of hydrogen and aluminum fluorides with a fluoride-selective electrode

Stability quotients for the hydrogen-fluoride and aluminum-fluoride systems in NH 4NO 3 were determined from measurements of free fluoride ion concentration by the lanthanum fluoride membrane electrode. Stability quotients at 0·5, 0·3, 0·1, and 0·01 M ionic strength were extrapolated to infinite dilution through the Debye-Hückel equation to obtain thermodynamic stability constants at 25°C for HF, HF 2 −, AlF 2+, AlF 2 +, AlF 3, and AlF 4 −.