Fluoride ion sensor electrodes that use polycrystalline LaF3 prepared by low‐temperature sintering can reduce sensor size and fabrication costs; however, decreasing the sintering temperature ...deteriorates sensor performance. Further, it is unclear why the performance of polycrystalline LaF3 prepared at low temperatures is inferior to that of the single‐crystal LaF3. Thus, in this study, we investigated factors that deteriorate sensor response under low sintering temperatures, such as solution penetration, fluorine conductivity, and ion exchange. To this end, LaF3 was prepared by changing the sintering temperature, and the electrical characteristics and sensor performance were evaluated and compared with those of the single‐crystal LaF3. The sensor performances of LaF3 sintered at 900 °C (−9.3 mV/dec) and 1000 °C (−5.8 mV/dec) were inferior to that of a single‐crystal LaF3 (−49.9 mV/dec). LaF3 prepared by sintering over 800 °C achieved fluorine removal and showed lower ion conductivity and ion exchange compared to that of the single‐crystal LaF3. LaF3 sintered at 700 °C did not show a sensor response because of solution penetration into the through‐pore. Our results confirmed that solution penetration, ion conductivity, and ion exchange influence the sensor performance of LaF3. Finally, we discussed approaches to achieve high sensor performance with LaF3 prepared by low‐temperature sintering. The proposed approaches are expected to contribute to expanding the utility of fluoride ion sensor electrodes with LaF3.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
An all‐solid‐state fluoride ion‐selective electrode (ISE) was prepared using LaF3 single crystal with poly(3,4‐ethylenedioxythiophene (PEDOT) as the solid contact layer. In contrast to polymer‐based ...ISEs, crystalline membrane‐based ISEs have not been used for all‐solid‐state device, thereby prohibiting the integration of ISEs on a chip. The all‐solid‐state fluoride ISE developed in this study exhibited superior sensitivity (−56.0±0.9 mV/dec) and selectivity compared to those of conventional inner filling solution ISE. The effects of PEDOT as a solid contact layer were analyzed using chronopotentiometry and electrochemical impedance spectroscopy, which revealed that PEDOT promoted electrode stability. The all‐solid‐state device can miniaturize the fluoride ISE and facilitate environmental, industrial, agricultural, and physiological monitoring.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The potentiometric analysis of the fluoride content (as F-ion) in toothpaste suspension with an ion-selective fluoride electrode is simple, reliable and inexpensive. Very low fluoride ion ...concentrations (up to 10–5 mol / l) can be determined with a fluoride-selective electrode, whereby the ionic strength of a solution is regulated and the concentration of hydroxide ions and interfering metal ions is controlled. The influence of the pH value and the complex ions of metals can be successfully regulated by the Total ionic strength adjustment buffer (TISAB) solution and by maintaining the pH value in the range from 5.00 to 8.00. The fluoride concentrations of 34 different toothpaste samples of different brands are determined using an ion-selective electrode. The highest value is 1285.85 ppm from Germany (Blend a. Med) and the lowest value is 18.15 ppm from Indonesia (Formula junior). Most of the low values are from Asian countries between (18.15-514.84) ppm, which are less than 600 ppm and this concentration is insufficient for Iraqi prescriptions and World Health Organization (WHO) specifications, the highest Values are between (940.66-1285.85) ppm, from Japan, USA and Germany
Pollution level and noncarcinogenic health risks due to fluoride and nitrate in the groundwater samples from Ramanathapuram district during pre-monsoon (September 2016) were calculated. One hundred ...and fifty-two groundwater samples collected were analysed for various physicochemical parameters such as major cations (Ca
2+
, Mg
2+
, Na
+
, K
+
) and major anions (CO
3
2-
, HCO
3
−
, SO
4
2-
, Cl
−
, NO
3
−
, PO
4
3-
). The fluoride ion concentrations in the collected samples were measured using the fluoride ion-selective electrode. Noncarcinogenic risks were calculated based on fluoride and nitrate concentrations (fluoride - 0.02-1.00 and nitrate - 0.0-4.9). The calculated risk values exceed the United States Environmental Production Agency (USEPA) recommended value of 1. The habitants from the study area are under the health risk due to fluoride and nitrate. Water quality index (WQI) values of the analysed samples indicate that 52% poor, 14% very poor, and 4% unsuitable for drinking purposes. Piper plot shows that 58% of mixed Ca
2+
-Mg
2+
-Cl
−
and 16% of Na
+
-Cl
−
groundwater types are predominant in the study area. Gibbs plot reveals that 91% of the samples have rock-water interaction, and it is a principal process that controls the dissolution of minerals from the subsurface into groundwater. Statistical analysis (correlation analysis, factor analysis) reveals that the natural process (rock-water interaction, leaching of sediments) and anthropogenic activities (domestic sewage, untreated effluents from industries) are the reason for the high fluoride and nitrate concentration in the groundwater. High noncarcinogenic health risk places were marked in spatial distribution maps.
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The presence of different species derived from hydrofluoric acid, together with the corresponding formation equilibria, has been investigated in 70% (w/w) ethanol/water solutions at analytical ...concentrations up to 5 mol L−1. In the same way, hydrofluoric acid solutions in 50% (w/w) (up to 2 mol L−1) and in 30% (w/w) ethanol/water (at 0.003–0.005 mol L−1) have been examined too. Conductometric and potentiometric (glass electrode and fluoride-ion-selective electrode) measurements have been used to demonstrate that HF and HF2− predominate in dilute solutions regardless the solvent composition, whereas HF and polyhomoconjugated species prevail in the concentrated ones.
Thermodynamic dissociation and homoconjugation constants have been determined in hydrofluoric acid dilute solutions. The more ethanol is contained in the solvent, the higher is the formation constant for the homoconjugated species (between 1.1 and 1.3 as logKhomo). In concentrated HF solutions at 70% and 50% (w/w) ethanol/water medium, the polyhomoconjugated species H2F3− (in 70% and 50% ethanol/water) and H3F4− (in 70% ethanol/water) are formed, with successive formation constants between about 4.1 and 6.9 logarithmic units, being the values obtained for the first homoconjugated species (about 1.2 in logarithmic units), very close to those obtained in dilute HF solutions.
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•The hydrofluoric acid solutions in ethanol/water media contain conjugated species.•The aggregation number increases with the ethanol content and the HF concentration.•The main species in high ethanol content solutions are HF and Hn−1Fn− (n: 0 to 4).•The HF is the predominant species in solution in the whole range studied.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Layered Double Hydroxide (LDH) is capable of fluoride anion exchange and release. This study investigated the effects of incorporating ZnAl-LDH in commercial and experimental dental varnishes, on ...fluoride release and re-release after charging in NaF.
Five discs of each material (commercial ClinproXT varnish and experimental light cured resin varnish), with and without 9%ZnAl-LDH were immersed and agitated in deionised water (DW) at 37 °C. A fluoride ion selective electrode measured fluoride release in DW daily over two-weeks. At 3, 6, 9 and 12 days the discs were recharged in 15 ml 0.05 M NaF solution (37 °C) for five minutes followed by immersion in DW. Energy dispersive X-ray spectra (EDS), weight changes and SEMs were performed on discs, before and after each cycle.
Evidence of ZnAl-LDH was confirmed by the presence of peaks for zinc and aluminium in EDS spectra. Cumulative fluoride and mean fluoride released between Clinpro, Clinpro + LDH and resin were significantly different (ANOVA, Tukey’s HSD post-hoc test, p < 0.001) except between the resin and resin + LDH. Mean fluoride concentrations differed significantly after every recharge between Clinpro, Clinpro + LDH and resin, but not between the resin and resin + LDH (p < 0.01). The weights and SEMs of the experimental resins +/-LDH, appeared to be stable whilst the weights of Clinpro samples +/−LDH, fluctuated and fragmented.
ClinproXT and experimental resin containing ZnAl-LDH recharged with fluoride did not significantly increase fluoride release compared to the unmodified materials. However, all LDH-F incorporated materials demonstrated fluoride recharging properties which appear beneficial to dentistry and thus further work is required to improve these properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Background/Aims: Currently available techniques for fluoride analysis are not standardized. Therefore, this study was designed to develop standardized methods for analyzing fluoride in biological and ...nonbiological samples used for dental research. Methods: A group of nine laboratories analyzed a set of standardized samples for fluoride concentration using their own methods. The group then reviewed existing analytical techniques for fluoride analysis, identified inconsistencies in the use of these techniques and conducted testing to resolve differences. Based on the results of the testing undertaken to define the best approaches for the analysis, the group developed recommendations for direct and microdiffusion methods using the fluoride ion-selective electrode. Results: Initial results demonstrated that there was no consensus regarding the choice of analytical techniques for different types of samples. Although for several types of samples, the results of the fluoride analyses were similar among some laboratories, greater differences were observed for saliva, food and beverage samples. In spite of these initial differences, precise and true values of fluoride concentration, as well as smaller differences between laboratories, were obtained once the standardized methodologies were used. Intraclass correlation coefficients ranged from 0.90 to 0.93, for the analysis of a certified reference material, using the standardized methodologies. Conclusion: The results of this study demonstrate that the development and use of standardized protocols for F analysis significantly decreased differences among laboratories and resulted in more precise and true values.
•The concentration of fluoride does not reflect the rate of fluoride release.•Calcium phosphate formula and/or additives would influence fluoride ion release.•CPP-ACP or Bioglass® could be source of ...bioavailable calcium and phosphate.
To compare ion release characteristics of three different dental varnishes either containing CPP-ACP and fluoride (CPP-ACPF, MI Varnish GC, Japan), bioactive glass and fluoride (BGAF, Dentsply Sirona USA) or fluoride alone (NUPRO White, Dentsply Sirona USA) using fluoride-Ion Selective Electrode (F-ISE), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), 19F and 31P Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR).
A thin layer (0.0674±0.0005g) of each varnish (20×25mm in area) was spread on a roughened glass slide (n=7). They were separately immersed in 10ml Tris buffer (0.06M, pH=7.30), and changed after 1, 2, 4, 6, 24 and 48h. Fluoride-ion concentration at each time using the F-ISE, whilst calcium and phosphate release were investigated using ICP-OES. XRD, FTIR. MAS-NMR analyses were also performed before and after immersion.
The cumulative F-ion release was significantly higher in CPP-ACPF (1.113mmol/g)>BGAF(0.638)>F(0.112) (p<0.001). The cumulative calcium and phosphorus were higher in the CPP-ACPF (0.137mmol/g, 0.119) than BGAF (0.067, 0.015) (p<0.001) respectively. The XRD and 19F MAS-NMR confirmed the presence of NaF peaks in all cases before immersion. There were less prominent signal and appearance of fluorapatite crystals after immersion. 19F MAS-NMR revealed CaF2 formation after immersion in both CPP-ACPF and BGAF. 31P MAS-NMR showed phosphate signals in both CPP-ACPF and BGAF before immersion. FTIR failed to show any signs of apatite formation.
Both CPP-ACP and bioactive glass enhanced ion release without compromising the bioavailability of fluoride. The CPP-ACPF varnish had the most promising ion release.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
► Human exposure to F from tea and from tea and diet assessed. ► Leaching and availability of F from teas of different types and forms studied. ► F leaching not affected by the type or form with the ...exception of Pu’erh tea. ► Consumption of 1000
ml of tea per day (person with 70
kg) provides 9–101% of AI. ► In nonfluoridated areas tea and diet can provide 25–173% of AI (in fluoridated 35–210%).
Human exposure to the fluoride (F) from commercial teas was assessed. The efficacy of the F leaching was determined from the total F (F
t) contents in the teas (53–435
mg/kg) and the F concentrations in tea infusions (0.31–3.55
mg/l of free F available to human organism). Both were determined with a fluoride ion selective electrode. The efficacies of F leaching from the green, oolong and black teas were 55–90% with continuous, and 74–100% by repeated infusions, and were not affected by the type or the manufactured form. Lower efficacies were observed from Pu’erh teas, 21–38% with continuous, and 37–59% by repeated infusions. The daily intake of F with daily consumption of five cups of tea can represent 9–101% of the adequate intake (AI) for an adult person with 70
kg, and with tea and diet 25–173% of the AI in non-fluoridated and 35–210% of AI in fluoridated areas. The upper limits of these intakes can be already associated with a risk of developing F-related adverse effects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
To quantify fluoride in food it is necessary to extract the fluoride from the matrix. Dry ashing (alkali fusion) and facilitated diffusion are the methods most commonly used, but their application ...requires lengthy treatments. The present study proposes the use of a microwave oven and 7 mol/L nitric acid for simple, rapid digestion of foods for fluoride analysis. The analyte is subsequently quantified by fluoride ion-selective electrode. The various steps of the method were optimized and an in-house validation was performed. The limit of quantification (0.130 mg/kg), trueness (92%), recovery (84–101%), and precision (1–8%) were determined. These analytical characteristics are satisfactory and show the suitability of the method for analysis of fluoride in foods of various kinds. The method’s ease of application and the use of equipment normally found in food analysis laboratories may help to further increase research on fluoride concentrations in foods consumed by the population.
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