Determination Of Fluoride Ion Research Articles

Water-Based Microwave-Assisted Digestion Method for Electrochemical and Chromatographic Determination of Total Fluoride Ions in Toothpaste Samples

Fluoride ions are the major constituents of dental products because they prevent cavities through bacterial growth inhibition. However, excessive consumption of fluoride ions results in fluorosis, thereby causing tooth staining and roughness. Therefore, there is a crucial need to develop rapid and effective methods for monitoring fluoride levels in dental products. The current study describes a greener water-based microwave-assisted digestion (WB-MAD) prior to fluoride-ion-selective electrode (F-ISE) measurement for the determination of fluoride ions in various toothpaste products. The optimum conditions of the developed WB-MAD method were 180 °C digestion temperature, 60 min digestion time, 0.05 g toothpaste amount and 10 mL distilled water. Under the optimum conditions, the method detection limit (MDL) of 0.00302 µg/kg and the method quantification limit (MQL) of 0.01007 µg/kg obtained were favorably comparable with the literature reports. The proposed WB-MAD method was both accurate (99.2 to 101%) and precise (≤0.75%) for the quantitative determination of F− in toothpaste samples using F-ISE. Furthermore, the newly developed WB-MAD method showed better accuracy (97–100%) than the traditional microwave-assisted acid digestion methods (71–92%). It is worth indicating that since water was used as the only digestion reagent, it was possible to validate the F-ISE results with ion chromatography (IC). The percentage recoveries obtained from IC (91–104%) and F-ISE (93–100%) were statistically insignificant. In view of the validation data, the proposed WB-MAD method can be considered as an alternative to the conventional microwave-assisted acid digestion (MAAD) methods for the determination of F− in toothpaste samples containing sodium monofluorophosphate.

Layered double hydroxide nanoparticles for a smartphone digital image colorimetry-based determination of fluoride ions in water, milk and dental products

A novel smartphone digital image colorimetry-based approach was developed for fluoride ion determination, using layered double hydroxide (LDH) nanoparticles (Mg2Al(OH)7) as sorbents for analyte preconcentration and as a source of a central metal ion for a colored complex formation. A cotton rotating disk provided effective retention of the LDH nanoparticles during solid-phase microextraction and elution, excluding time-consuming centrifugation process. In the proposed procedure, the nanoparticles acted as aluminum ion source for alizarin complexone-Al3+-F– complex formation. An image of Eppendorf tube, containing the colored complex solution was obtained by a smartphone and converted, using the RGB model for fluoride ion determination. The procedure had a linear range of 0.20–20 mg L−1 with a limit of detection of 0.06 mg L−1. The developed procedure provided effective fluoride separation from various matrices for its determination by a smartphone without additional sample pretreatment.

ЭКОЛОГИЧЕСКИЙ КОНТРОЛЬ СТОЧНЫХ ВОД В ПРОМЫШЛЕННОСТИ

The issues of application of potentiometric method of determination of fluoride ions and chloride-ions in industrial wastewater of cooling section of rolling workshop were discussed. The results of their determination were validated by comparing the results of several parallel measurements using standardized methods. Comparison of the obtained results of fluoride and chloride content in industrial wastewater samples with sanitary and epidemiological standards was conducted.

Silver-ligand complex as an additive in polymeric membranes of screen-printed fluoride-selective electrodes

Fluoride-selective electrodes with membranes containing zirconium porphyrin and dithizone-silver complex were developed. Silver disc electrodes and devices fabricated by screen-printing with silver ink were used as transducers. Dithizone-silver complex ensures potential stability of prepared electrodes, forming a redox couple with silver metal transducers. Moreover, it serves as lipophilic cationic site in the membrane, inducing zirconium porphyrin to act as a neutral ionophore. Electrodes with these membranes showed the following selectivity sequence: ClO4− > F− > NO3– > Cl−. Linear response towards fluoride was observed from 10−4 M to 10–1 M. Charged carrier mechanism is also possible, requiring polar plasticizer and addition of anionic lipophilic sites to the membrane. While membranes with ionophore working as charged carrier show better discrimination of lipophilic anions (selectivity sequence: F− > ClO4− > NO3– > Cl−), dynamic range of fluoride response is narrower in this case (10−4 M to 10−2 M), as compared to membranes with ionophore working as neutral carrier. Screen-printed electrodes with membranes containing dithizone-silver complex were integrated with reference electrodes with membranes containing ionic liquid, prepared on the same transducers. These devices were successfully employed for determination of fluoride ion in pharmaceutical samples.

Fluoride ions detection in aqueous media by unprecedented ring opening of fluorescein dye: A novel multimodal sensor for fluoride ions and its utilization in live cell imaging

Imidazole functionalized on fluorescein dye was developed as an efficient probe for naked eye and fluorescence determination of fluoride ions. The probe is dramatic color change and very exciting fluorescence turn-on response with the addition fluoride ions. Moreover, fluoride ions triggering leads to the fissure of the spirolactam ring that causes drastic color makes feasible for the naked eye detection of fluoride ions. The mode of binding of fluoride with the probe was proved by 1H NMR titration experiments and the observed photophysical changes were rationalized by use of DFT calculations. This sensor was more applied to detect fluoride ions in real samples and imaging of fluoride ions through fluorescence imaging in living cells.

A novel potentiometric sensor for determination of fluoride ion based on ionophore N,N’-Ethylene-bis(salicylideneaminato) nickel (II)

The N, N’-Ethylene-bis(salicylideneaminato) nickel(II) ionophore was synthesized and characterized by IR, NMR and C, H, N analysis. Polyvinyl chloride (PVC)-based membrane sensors of ionophore (I) with cation discriminator cetyl trimethylammonium bromide (CTAB) were prepared using different plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), 1-chloronaphthalene (CN), and tri-n-butylphosphate (TBP). Among the several membrane sensors prepared, the one having membrane composition in the ratio of 1: 33: 65: 1 mg (I: PVC: DBP: CTAB) showed best performance. This sensor performed well over a wide concentration range of 5.9 × 10−6–1.0 × 10−1 M with a detection limit of 3.6 × 10−6 M and slope of 57.2 ± 0.2 mV per decade. The proposed sensor can be used in the wide pH range (2.1–9.1) and showed a quick response time of 22 s. The selectivity coefficient values calculated using the fixed interference technique (FIM) exhibit that the sensor has good selectivity for fluoride ions over a large variety of anions. The sensor showed a shelf life of 50 days and during this period the results were highly reproducible. The sensor was successfully utilized for the detection of fluoride ions in drinking water and tea sample.

Indirect Differential Pulse Voltammetric Determination of Fluoride Ions at Carbon Paste Electrode Modified with Porous and Electroactive Fe3+/Fe2+ Based-Metal Organic Frameworks Type MIL-101(Fe)

An innovative and reliable electrochemical sensor was proposed for simple, sensitive and selective determination of F− ions. The sensor based on the fabrication of porous and electroactive Fe-based metal organic frameworks [MIL-101(Fe)]. It was blended with graphite powder and liquid paraffin oil to from carbon paste electrode (CPE). The MIL-101(Fe)@CPE was characterized using different techniques such as scanning electron microscope, powder X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray, cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry. The MIL-101(Fe)@CPE exhibited two redox peaks (anodic and cathodic) corresponding to Fe3+ and Fe2+, respectively. The determination of F− ions based on the formation of a stable fluoroferric complex with Fe3+/ Fe2+, decreasing the currents of redox species. It was found that the anodic peak current (Ipa) is linearly proportional to the concentration of F− in the range of 0.67–130 μM with a limit of detection (S/N = 3) of 0.201 μM. The electrode exhibited good selectivity towards F- detection with no significant interferences from common anions. The as-fabricated sensor was applied for the determination of F− in environmental water samples with recoveries % and RSDs % in the range of 98.1%–102.4% and 2.4%–3.7%, respectively.

Selective and Fast Detection of Fluoride-Contaminated Water Based on a Novel Salen-Co-MOF Chemosensor.

The development of selective and fast optical sensitive chemosensors for the detection and recognition of different cations and anions in a domain is still a challenge in biological, industrial, and environmental fields. Herein, we report a novel approach for the detection and determination of fluoride ion (F–) sensing based on a salen-cobalt metal-organic framework (Co(II)-MOF). By a simple method, the Co(II)-MOF was synthesized and characterized using several tools to elucidate the structure and morphology. The photoluminescence (PL) spectrum of the Co(II)-MOF (100.0 nM/L) was examined versus different ionic species like F–, Br–, Cl–, I–, SO42–, and NO3– and some cationic species like Mg2+, Ca2+, Na+, and K+. In the case of F– ions, the PL intensity of the Co(II)-MOF was scientifically enhanced with a remarkable red shift. With the increase of F– concentration, the Co(II)-MOF PL emission spectrum was also professionally enhanced. The limit of detection (LOD) for the Co(II)-MOF chemosensor was 0.24 μg/L, while the limit of quantification (LOQ) was 0.72 μg/L. Moreover, a comparison of the Co(II)-MOF optical approach with other published reports was studied, and the mechanism of interaction was also investigated. Additionally, the applicability of the current Co(II)-MOF approach in different real water samples, such as tap water, drinking water, Nile River water, and wastewater, was extended. This easy-to-use future sensor provides reliable detection of F– in everyday applications for nonexpert users, especially in remote rural areas.

Determination of trace fluoride in water samples by silylation and gas chromatography/mass spectrometry analysis.

Due to the ubiquity of fluorides and the small gap between a safe dose and a harmful one, it is necessary to develop a robust analytical method for determination of fluoride ions in various water samples with complex matrices. Silylation of the fluoride ion was carried out by treatment with hydrochloric acid and phenyldimethylchlorosilane at room temperature. The formed phenyldimethylfluorosilane was detected by gas chromatography/mass spectrometry (GC/MS). Under the optimized conditions, linearity in the analytical method ranged from 0.050 to 5.0 μg/mL for the fluoride ion with R2 >0.9999. Reasonable reproducibility was obtained with the intraday relative standard deviation (RSD) (N = 5) of 2.04% and interday RSD (N = 5) of 3.75% at the concentration of 0.10 μg/mL. The developed method has been successfully applied to determine the fluoride ion in real water samples, including waste water samples, with the recovery between 81.12% and 113.04%. A robust method for the determination of the fluoride ion has been developed by silylation with phenyldimethylchlorosilane and GC/MS analysis. The established method showed good anti-interference and precision, and it has been applied for determination of the fluoride ion in various water samples.

Zirconium gallocyanin MS complex as a highly selective reagent for the spectophotometric determination of fluoride

A new photometric procedure for the determination of fluoride ion based on its destruction of zirconium-gallocyanin MS complex is described.The method exhibits great selectivity towards fluoride compared to alkaline-earth, non-ferrous and rare-earth metals, iron, sulfate, nitrate, and phosphate ions and allows to carry out the determination of fluoride in complex objects complex without a preliminary separation of matrix components. The linear range of the quantitative determination of F− was determined to be 0.03 to 2 mg/L with a detection limit of 0.02 mg/L and a correlation coefficient of 0.9989. This method has been successfully applied to the determination of fluorides in natural waters, metallurgic wastewaters, cryolite and condensates of volcanic gases and has good convergence with the results of potentiometric analysis.

Synthesis of yttrium(III)-based rare-earth metal-organic framework nanoplates and its applications for sensing of fluoride ions and pH

High-performance determination of fluoride ion (F−) is an important goal due to the hazards of fluoride to human body. In this study, a rare-earth metal-organic frameworks (RE-MOFs) was successfully designed and prepared with a nanoplates morphology. 4,4,4,4-(Porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (called “TCCP”) as the porphyrin-based planar ligand and Y3+ as the metal center were applied to form the Y-TCCP MOF nanoplates (YTMNs) via coordination chelation. Giving the credit to the distinctive host-guest response between YTMNs and F− (or OH−), a multipurpose fluorescence sensor was developed with multiple signal output. F− reacted with YTMNs and light-up the fluorescence of YTMNs under the pH of 6. Thus YTMNs was exploited as a fluorescence nanoprobe for F− detection with high sensitivity and selectivity. In addition, it was found that the alkaline medium (pH > 7) also induced the strong fluorescence of YTMNs. These two phenomena occurred at different pH ranges. Therefore, F− detection and pH sensing were simultaneously realized by YTMNs nanoprobe. More importantly, the paper-based YTMNs strip was prepared for visual sensing of pH. The detection results of YTMNs strip were further analyzed by an Intelligent Identification System for Visual Chip (IISVC) for monitoring of pH with digital output. Additionally, the accuracy of YTMNs nanoprobe was confirmed by determination of F− in natural water and pH in real water.

Design, synthesis and applications of fluoride probe based on aromatization of isoquinolinium salts

A novel ratiometric fluorescent probe based on aromatization drive of isoquinolinium salts was designed, synthesized to recognize fluoride. The applications have shown that the probe has high selectivity and sensitivity to fluoride. Fluoride induces a cascade reaction of hydroxyl deprotection and 1,6-oxidative elimination, and causes a remarkable fluorescence enhancement. The relative fluorescent intensities (I398/I522) increased linearly with F− concentration in the range of 0–9.0 μmol L−1. The limit of detection was very low (3.7 nM) due to the intrinsic aromatization drive of probe induced by F−. The recognition mechanism was demonstrated by mass spectrum (MS) and 1H NMR. The in vitro imaging results showed that the new probe BIQS (2-[4-(tert-butyl-diphenyl-silanyloxy)-benzyl]-3-(4-methoxy- phenyl) -isoquinolinium nitrate) was membrane-permeable and could be applied into the determination of fluoride ions in living cells.

Luminescent metal organic frameworks–based chemiluminescence resonance energy transfer platform for turn–on detection of fluoride ion

A luminescent metal organic frameworks (MOFs)–based chemiluminescence resonance energy transfer (CRET) platform was constructed for turn–on detection of fluoride ion. A hybrid MOFs was prepared by encapsulating strong fluorescence 2′,7′–dichlorofluorescein (DCF) into the frames of NH2–MIL–101(Al) MOFs, which led to a significant suppression of fluorescence signal of DCF. In the presence of fluoride ion, it destroyed the structure of the hybrid MOFs and released DCF molecules from the frames due to the formation of more stable aluminum hexafluoride complex ions [AlF63−] between fluoride ion and aluminum ion. The released DCF molecules accepted the energy originating from the chemical reaction of bis(2,4,6–trichlorophenyl)oxalate (TCPO) with hydrogen peroxide (H2O2), producing a strong chemiluminescence (CL) emission. The CL signal was strong dependent on the concentration of fluoride ion presented and showed a linear response in the range of 0.5–80.0 μmol L−1 (9.5 μg L−1–1.52 mg L−1). The detection limit was 0.05 μmol L−1 (about 0.95 μg L−1) fluoride ion and the relative standard deviations was 2.3% for 40.0 μmol L−1 fluoride ion solution (n = 11). This MOFs–based CRET method was successfully applied to the determination of fluoride ion in drinking water samples, demonstrating its potential application in analysis of real samples.

ANALYSIS AND EVALUATION OF BLOOD PLASMA PROTEOMIC PROFILE VIOLATIONS DUE TO THE INCREASED CONCENTRATION OF FLUORIDE ION IN CHILDREN’S URINE

We evaluated the air quality by the content of fluorine-containing compounds according to monitoring studies, chemical and analytical determination of fluoride ion in urine and performed proteomic analysis of blood plasma in children of the observation and comparison group. The increased content of fluoride ion in the urine was found in children of the observation group relative to the same indicator in children of the comparison group and the reference level in conditions of poor air quality for the hydrofluoride content due to the economic activity of aluminum production facilities. The concentration of fluoride ion in the urine is justified as a marker of inhalation exposure. A comparative analysis revealed the presence of significant differences in the relative volume of protein spots. Mass spectra were obtained that contain information about the peptides included in the composition of the studied protein set and the genes encoding identifiable proteins were established.

ANALYSIS AND EVALUATION OF BLOOD PLASMA PROTEOMIC PROFILE VIOLATIONS DUE TO THE INCREASED CONCENTRATION OF FLUORIDE ION IN CHILDREN’S URINE

We evaluated the air quality by the content of fluorine-containing compounds according to monitoring studies, chemical and analytical determination of fluoride ion in urine and performed proteomic analysis of blood plasma in children of the observation and comparison group. The increased content of fluoride ion in the urine was found in children of the observation group relative to the same indicator in children of the comparison group and the reference level in conditions of poor air quality for the hydrofluoride content due to the economic activity of aluminum production facilities. The concentration of fluoride ion in the urine is justified as a marker of inhalation exposure. A comparative analysis revealed the presence of significant differences in the relative volume of protein spots. Mass spectra were obtained that contain information about the peptides included in the composition of the studied protein set and the genes encoding identifiable proteins were established.

Spectrophotometric methods for the determination of fluoride ion usingindole-3-acetic acid interaction with iron(III)

This study is related to the determination of fluoride ion by the conversion of pink-colored Fe(III) and indole-3-acetic acid (IAA) into a colorless hexafluoride ferrite complex with the addition of fluoride. The optimum conditions of the complex formation were found to be pH 1.7 and a temperature of 60 $^{\circ}$C C. The maximum absorption wavelength of the complex and the detection limit of the method were 525 nm and 0.26 mg/L, respectively. The interfering effects of the different cations (Ag$^{+}$, Al$^{3+}$, Ba$^{2+}$, Ca$^{2+}$, Cd$^{2+}$, Co$^{2+}$, Cu$^{2+}$, K$^{+}$, Mg$^{2+}$, Na$^{+}$, Ni$^{2+}$, Pb$^{2+})$ and anions (SO$_{4}^{2-}$, SO$_{3}^{2-}$, NO$_{2}^{-}$, I$^{-}$, Br$^{-}$, Cl$^{-}$, SCN$^{-}$, CH$_{3}$COO$^{-}$, H$_{2}$PO$_{4}^{-}$, ClO$_{4}^{-})$ were also investigated. The method was applied to standard and real samples and the resulting data were statistically compared at a confidence level of 95{\%} with those obtained with the use of a fluoride-selective electrode.

Imaging-based fluorescent sensing platform for quantitative monitoring and visualizing of fluoride ions with dual-emission quantum dots hybrid

Herein, a ratiometric fluorescence sensing strategy coupled with smartphone imaging-based sensing platform was proposed for the on-site determination of fluoride ion (F−) with high sensitivity and accuracy. The principle of sensing strategy is based on the fluoride-promoted Si–O bond cleavage of 2-(tert-butyldiphenylsilyloxy)phenol (2-TBDPSP) to release 2-hydroxyphenolate, which rapidly auto-oxidized to ortho-quinone. As excellent electron acceptor, these quinone species covalently bonded on the surface of dual-emission amino-modified quantum dots (QDs) nanohybrid via a Michael's type adduction, quenching the fluorescence of green-emitting QDs on the surface of the nanohybrid, while not affecting the fluorescence of red-emitting QDs embedding silica nanospheres. Upon exposure to different amounts of F−, the variations of dual emission intensity ratios display continuous color changes from green to red, which could be directly observed by naked eyes. Then a smartphone imaging-based sensing platform was constructed by 3D-printing technology. The smartphone camera acquired the images of fluorescence derived from samples, and the Color Picker APP installed in smartphone continued to read out the Red, Green and Blue (RGB) channel values of these images. There was a linear relationship between the ratio of Red and Green (R/G) and F− concentration in the range of 0–70.0 μM. The limit of detection (LOD) was estimated to be 2.0 μΜ, much lower than the allowable level of F− (~63.16 μM) in drinking water set by World Health Organization. This methodology reported here is low-cost, portable, easy-operation, and thus potentially attractive for F− determination without the need of elaborate equipment.

A semi quantitative visual probe for fluoride ion sensing in aqueous medium

High toxicity and widespread availability of fluoride ions in different environmental matrices prompted attention for designing an efficient probe for its detection. Given this, a new sensor based on coumarin 343 (C343) dye and Eu3+ is designed and working mechanism of probe was understood using steady state optical absorption and emission and time resolved emission studies. The designed probe is free of tedious synthetic procedure and sophisticated instrumentation and is highly selective. A general procedure is designed for fluoride ion detection in samples and it was observed that fluoride ion concentration well below 2 ppm can be detected visually, a limit set by WHO for fluoride ion in drinking water. The suggested probe was also tested for fluoride ion concentration in the real sample and it was observed that the result matches well with the values obtained from standard technique. The designed probe is economical, rapid, selective and most importantly can be used directly for fluoride ion determination in real aqueous samples.

Potentiometric Micromethod for The Determination of Fluoride Ion in Natural Objects

Potentiometric Micromethod for The Determination of Fluoride Ion in Natural Objects

A single nanofluorophore "turn on" probe for highly sensitive visual determination of environmental fluoride ions.

Herein, we report a single nanofluorophore “off–on” probe based on the unique fluoride–boron interaction to achieve the visual determination of fluoride ions in environmental water. Red quantum dots (QDs) were modified using 3-aminophenylboronic acid (APBA) to form a stable standard emission probe, and reaction of the probe with catechol formed a five-membered cyclic borate ester, which led to the quenching of the fluorescence emission. The designed nanofluorophore probe showed a turn-on effect in the presence of fluoride ions due to the five-membered cyclic borate ester being transformed into a trifluoroborate, with breakage of the B–O bonds and removal of the catechol from the QDs. The prepared nanofluorophore probe displayed a high sensitivity for the quantification of fluoride ions with a naked eye visual detection limit of 0.4 μM, which was much lower than the US Environmental Protection Agency (EPA) defined limit (37 μM). Furthermore, the probe displayed an effective application for the detection of fluoride ions in environmental samples such as tap water and lake water. The very simple method reported here could be extended to the visual detection of a wide range of analysis assays in natural samples.