Determination Of Fluoride Research Articles

A highly sensitive fluorimetric method for the determination of fluoride in biological material with Al3+-calcein complex.

A highly sensitive fluorimetric method for the determination of fluoride was established. The method was based on quenching of the fluorescence of the Al3+-calcein complex in CCl3COOH-CH3COOK buffer solution by fluoride. The fluorescence emission was measured at lambdaex/lambdaem 480/503 nm, and the experimental variables and interference in this determination were studied. The linear calibration range was 0.8 ng/mL to 150 ng/mL and the detection limit was 0.2 ng/mL. The method was applied to determine fluoride in biological materials. The recovery was in the range of 96.3% to 104.7% and the relative standard deviation was 4.6%. The results obtained from the certified reference material by the present method agreed with the certified values.

Determination of fluoride in M(SbF 6) x compounds

The purpose of this study was to develop an analytical procedure to establish both the yield and purity of co-ordination compounds of the type M(SbF 6) x , where M=Mn, Pr, La or Ce, synthesised in our laboratory. Such an analysis requires an accurate determination of the metal concentration, the amount of SbF 6 − species and free and total fluoride. In this study, free and total fluoride were determined using a fluoride ion selective electrode (ISE) with the analytical technique adapted to the sample decomposition/pre-treatment procedure. Initial attempts, using alkaline carbonate fusion with NaKCO 3 and alkaline microwave decomposition/fusion failed to ensure the complete release of fluoride, leaving 25–35% of F − still bound. Good quantitative recovery of fluoride (>99%) and the complete decomposition of the samples were achieved by the reduction of Sb(V) to Sb(III) using Devarda’s alloy in strongly alkaline media. To avoid any error arising in the determination of fluoride by ISE, interference due to Sb 3+ and Al 3+ — originating from the Devarda’s alloy, was masked by the addition of diaminocyclohexanetetraacetic acid (CDTA)/citrate buffer and the calibration of the fluoride electrode was made using standards containing all the reagents used during sample decomposition/preparation. Antimony and fluoride did not interfere with the complexometric determination of manganese with ethylenediaminetetraacetic acid (EDTA).

Determination of fluoride impurities in Leuprolide. Comparison of analytical methods

Fluoride impurities were determined in technical samples of Leuprolide (anti-cancer drug for prosthetic cancer) using reverse-phase liquid chromatography and derivative spectrophotometry. The chromatographic method was based on the ternary fluoride complex with zirconium(IV) and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). The analysis was performed on a Nucleosil C 18 column with LiChrosphere RP-100 end-capped phase, using as eluent acetonitrile (85%v/v) water mixture at pH 4.1±0.2. Fluoride content was determined with use of the method of standard additions (MOSA) as 2.34 mg g −1 and 0.29 mg g −1 in two different samples. A spectrophotometric determination has been carried out by La(III)-F −-ALC [ternary complex La(III)-F −-alizarin complexone] method with using third derivative spectrophotometry. By this method fluoride content was determined as 1.99 mg g −1 and 0.34 mg g −1 in the samples previously analyzed chromatographically. A validation for both (i.e. chromatographic and spectrophotometric) methods was performed. Statistical analysis showed that spectrophotometric methods could not be used for quantitative determination of fluoride in samples containing them in concentration less than 0.5 mg g −1.

Comparison of Fluoride Ion-Selective Electrode Based Potentiometric Methods of Fluoride Determination in Human Urine

Comparison of Fluoride Ion-Selective Electrode Based Potentiometric Methods of Fluoride Determination in Human Urine

Integrated pervaporation/detection for the determination of fluoride in pharmaceuticals

A selective dynamic method for the determination of fluoride in pharmaceuticals based on the integration of pervaporation and potentiometric detection in a laboratory-made module is proposed. The analyte was continuously converted into volatile trimetylfluorosilane by reaction with hexamethyldisilazane, injected into a donor stream and accepted in a basic buffer solution after pervaporation. The method thus developed has a determination range between 1.5 and 200 mg l −1, precision (expressed as R.S.D.) of 3.4%, and has been applied to the determination of fluoride in different pharmaceutical products, with yields ranging between 90.6 and 100.3%.

Evaluation of different SIA sample–buffer configurations using a fluoride-selective membrane electrode as detector

The peak profiles of four different buffer–sample SIA configurations, e.g. buffer–sample; sample–buffer; buffer–sample–buffer and sample–buffer–sample with the last two in the sandwich mode were evaluated with a fluoride-selective membrane electrode as detector. The best response characteristics and peak shapes as well as recovery and precision values were obtained for the buffer–sample configuration. For low concentration levels, sandwich SIA configurations are more suitable, when optimum buffer and pH are used. The utilisation of a cheap electrolyte with a minimum consumption of buffer and a cheap, robust instrumentation made the SIA system suitable for on-line determination of fluoride.

Hydrothermal synthesis and structure determination of a new aluminium phosphate fluoride: Sr3Al2(HPO4)F10

Crystals of the new fluorophosphate Sr3Al2(HPO4)F10 were grown by a high-temperature, high-pressure hydrothermal method (973 K, 180 MPa, 24 h) and structurally characterised by single-crystal X-ray diffraction. Sr3Al2(HPO4)F10 crystallises in the monoclinic system (space group P21/c, no. 14) with cell parameters at 293 K: a=7.309(3) Å, b=7.115(6) Å, c=20.45(1) Å, β=91.56(2)°, V=1063(1) Å3 and Z=4. Its structure is based on finite clusters of tetrahedra and octahedra of the form [Al2(HPO4)F10]. Inter-cluster linkage is quite complex due to the presence of O2− and F− as ligands in the cluster and Sr2+ as interstitial cations.

Phosphate rock treatment with citric acid for the rapid potentiometric determination of fluoride with ion-selective electrode

A fast method for sample treatment of phosphate rock has been developed for the purpose of quantitative leaching (98–100%) of fluoride but less of the interfering cations such as iron and aluminum. Citric acid (0.5 M) was used to extract fluoride in 15–45 min. Leaching of iron and aluminum is minimal, and these ions are complexed with citric acid. The leaching method was optimized with respect to sample size, citric acid concentration, leaching time and temperature. The analysis was completed by the rapid determination of fluoride with ion-selective electrode. The proposed treatment method was applied to phosphate rock samples from Jordan and Morocco and yielded accurate results as compared to the standard steam distillation from strong acid solution followed by thorium nitrate titration.

DETERMINATION OF SOLUBLE FLUORIDE AND MONOFLUOROPHOSPHATE IN DENTAL CREAM USING GRADIENT ELUTION ION CHROMATOGRAPHY

A single column, stability indicating, Ion Chromatographic method has been developed for the determination of Soluble Fluoride and Monofluorophosphate (MFP) in dental cream. The limits of detection (3x signal-to-noise) for Fluoride and MFP in dental cream are 5.0 ppm and 87 ppm (wt./wt.), respectively, using the sample preparation procedure described. These LODs correspond to operating concentrations of F and MFP of 0.05 ppm and 0.87 ppm (wt./vol), respectively. The method is linear for F− (r = 0.9998) over an operating range of 1.0 to 4.5 ppm (wt./vol) (40%–180% of 2.5 ppm target) and for MFP (r = 0.9999) over an operating range of 35.7 to 66.3 ppm (wt/vol) (70%–130% of 51.0 ppm target). Both anions (MFP and F) were found to have no interference with a placebo dentifrice and each passed resolution and tailing factor requirements of R ≥ 2.0 and T<1.5. Quantitative recoveries were obtained for both species from placebos spiked with 70, 100, and 130% of target. Twenty replicate preparations and analyses of a homogenized commercial sample, conducted by two operators over the course of 4 days, showed agreement to within 5.5%RSD for F and 2.23%RSD for MFP.

Flow injection analysis of fluoride: optimization of experimental conditions and non-linear calibration using artificial neural networks

This paper deals with the application of artificial neural networks (ANNs) to two common problems in spectroscopy: optimization of experimental conditions and non-linear calibration of the result, with particular reference to the determination of fluoride by flow injection analysis (FIA). The FIA system was based on the formation of a blue ternary complex between zirconium(IV), p-methyldibromoarsenazo and F- with the maximum absorption wavelength at 635 nm. First, optimization in terms of sensitivity and sampling rate was carried out by using jointly a central composite design and ANNs, and a neural network with a 3-7-1 structure was confirmed to be able to provide the maximum performance. Second, the relationship between the concentration of fluoride and its absorbance was modeled by ANNs. In this process, cross-validation and leave-k-out were used. The results showed that good prediction was attained in the 1-4-1 neural net. The trained networks proved to be very powerful in both applications. The proposed method was successfully applied to the determination of free fluoride in tea and toothpaste with recoveries between 96 and 101%.

Determination of Total Fluoride in Oral Products by Using of Potentiometry With Ion Selective Electrode: A Critical Study

ABSTRACT In this work, a critical study of the determination of fluoride in oral products with an ion selective electrode was performed. The influence of the type of fluorine compound in the sample as well as the practical factors involved in the analysis were investigated. Fluoride could be determined, directly, in samples where it is in the form of NaF or SnF2. However, in samples where it is as MFP (sodium monofluorophosphate) an acid treatment was needed for removal of fluoride from the PO4F2− ion. In both cases, problems were noted related to the continuous use of the electrode, caused by the adsorption of fluoride ions onto the electrode surface. This problem was solved by using of KOH and Al2(SO4)3 solutions. Good results were obtained for the analysis of real commercial samples.

Determination of Total and Fluoride Bound Aluminium in Tea Infusions by Ion Selective Electrode and Flame Atomic Absorption Spectrometry

ABSTRACT Speciation of metallic compunds is important especially for their bioavailability. In this present study fluoride bound aluminium species were determined in tea infusion. Total aluminium was measured using flame atomic absorption spectrometry (FAAS). Free fluoride and total fluoride were measured by fluoride selective ion electrode (FISE) with the assistance of TISAB buffer solution used for adjustment of pH and total ionic strength, and ALCOA buffer solution which decomposes all of the Al-fluoride complexes in solution. During the studies, the effects of pH and time on the formation of Al-F complexes and interference of some metal ions found in tea infusion such as Al3+, Mg2+, Fe2+, Fe3+ and Mn2+ on the concentration of free fluoride were investigated. The concentration of each Al-fluoride complexes in tea fusion were determined indirectly by calculation using pF-Mole Fraction Diagram. It was found that 1.13±0.15 mg 1− of 12.00±0.86 mg 1− total aluminium is fluoride bound aluminium, which means that appoximately 10% of total aluminium in tea infusion is complexed with fluoride.

Biological monitoring of exposure to sevoflurane in operating room personnel by the measurement of hexafluoroisopropanol and fluoride in urine

The objectives of this study were to evaluate the value of urinary hexafluoroisopropanol (HFIP) and fluoride (F-) measurement for the biological monitoring of operating room personnel exposed to sevoflurane. Fifty members of operating room staffs from eight different hospitals took part in the study. To assess external exposure to sevoflurane, air samples were collected during the whole anaesthesia period by a passive sampling device (3M 3500 organic vapour monitor) attached close to the breathing zone of each subject. Urine was collected before (BA) and at the end of anaesthesia (EA) for the determination of HFIP, fluoride and creatinine. Average airborne concentration of sevoflurane was 19.0 ppm (range: ND-139.9 ppm) with a mean duration of anaesthesia of 221 min (range: 60-435 min). There was a better correlation between external and internal exposure as estimated by EA urinary HFIP (r = 0.78; p <0.0001) compared with EA urinary F- (r = 0.41; p = 0.0031). Furthermore determination of urinary HFIP seemed more suited than that of F- for the assessment of sevoflurane exposure because of lower background in BA samples (86 % of BA HFIP values were under the limit of detection). Based on these results, values of 9.6 and 4.3 mg HFIP g-1 creatinine correspond to airborne concentrations of 50 and 20 ppm of sevoflurane, respectively. Among the confounding parameters investigated (body mass index (BMI), sex, cytochrome P450 polymorphism) only BMI showed statistically significant influence on sevoflurane metabolism at these low levels of exposure. The measurement of HFIP in urine at the end of the surgical procedure constitutes a good index to assess occupational exposure to sevoflurane. Further studies will be necessary to propose an health-based limit value which remains to be determined from the relationship between effects and internal dose as can be assessed by HFIP measurement in urine.

Trace determination of fluoride using lanthanum hydroxide supported on alumina

Lanthanum hydroxide supported on alumina has been studied to sorb fluoride ion from aqueous solutions. The adsorbent is effective in decreasing fluoride ion concentration from 7 mM to 0.003 mM in the pH range 5.7–8.0. The rate constant for sorption was found to be 6x10‐2 min‐1. The sorption of fluoride is Langmuir type and its capacity is 0.82 m M F‐/g of the adsorbent. The sorption selectivity shows that fluoride removal is affected by the presence of phosphate and sulphate but not affected by chloride, bromide iodide and nitrate ions. Alumina impregnated with lanthanum hydroxide has adsorption capacity in the range 0.340–0.365 mM/g. The removal of fluoride from industrial waste water is more than 96%. Fluoride ion sorbed can be eluted from the adsorbent with 10 mL of 0.1 M NaOH and the column can be reused after being conditioned with 10 mL of 1 mM hydrochloric acid. Results obtained by batch as well column methods are in good agreement with each other.

Simultaneous flow injection determination of calcium and fluoride in natural and borehole water with conventional ion-selective electrodes in series

An on-line automated system for the simultaneous flow injection determination of calcium and fluoride in natural and borehole water with conventional calcium-selective and fluoride-selective membrane electrodes as sensors in series is described. Samples (30 μl) are injected into a TISAB II (pH=5.50) carrier solution as an ionic strength adjustment buffer. The sample-buffer zone formed is first channeled to a fluoride-selective membrane electrode and then via the calcium-selective membrane electrode to the reference electrodes. The system is suitable for the simultaneous on-site monitoring of calcium (linear range 10 −5–10 −2 mol l −1 detection limit 1.94×10 −6 mol l −1 recovery 99.22%, RSD<0.5%) and fluoride (linear range 10 −5–10 −2 mol l −1 detection limit 4.83×10 −6 mol l −1 recovery 98.63%, RSD=0.3%) at a sampling rate of 60 samples h −1.

Zr(iv)‐spadns flow analysis procedure for determination of fluoride in surface and groundwater

A simple, fast and selective flow injection analysis (FIA) procedure for monitoring of fluoride in surface and ground water has been developed. The method is based on destruction of Zr(IV)‐SPADNS [2‐(p‐sulphophenylazo)1,8‐dihydroxynaphthalene‐3,6‐disulphonic acid trisodium salt] complex with fluoride ions in the presence of neutral surfactants i.e., TX‐100, TX‐300. The apparent molar absorptivity of the complex in term of fluoride lies in the range of (2.70‐ 5.20) × 103 Lmole‐1cm‐1 at absorption maximum 580 nm, depending upon acidity. The detection limit is 9 ppb F‐ at 4M HCl. The sample throughput is 80 samples/hr. Optimization of FIA variables and detailed studies of interferences of sulfate and phosphate with respect to acidity and sample volume injected were carried out. None of the tested ions interfere in the determination of F‐. The levels of fluoride pollution in the surface and groundwater of central India and their sources have been delineated.

Polarographic determination of trace fluoride in foods

This paper describes a polarographic method for the determination of trace of F - in mineral water, tap water, table salts, maize and rice using a dropping mercury electrode(DME). In La(III)ALC(CH 2) 6N 4 system (pH=4.9), (LaALC) 2F 2 complex gave a peak potential at −0.64 V versus SCE. The peak height was directly proportional to F − in the concentration range 8×10 −8 M–1×10 −6M. The limit of detection was 5×10 −8 M.

Determination of fluoride in toothpaste, effluent streams and natural and borehole water using a flow injection system with a fluoride-selective membrane electrode

An automated system for the determination of fluoride in toothpaste, effluent streams, natural and borehole water based on the concept of flow injection with a fluoride-selective membrane electrode as sensor is described. The system is suitable for the on-line monitoring of fluoride at a sampling rate of 60 samples h −1 in the linear range 10 −4 –10 −1 (approximately 1.9–1900 mg l −1 ) with an RSD of better than 0.6%.

Semiconductor sensors for the detection of fluorocarbons, fluorine and hydrogen fluoride

The sensitivity of metal–insulator–semiconductor structure gas sensors based on silicon or silicon carbide to different fluorine-containing gases was studied in the temperature range 20–530°C. Silicon based gas sensors could be used for the determination of fluorine and hydrogen fluoride at room temperature. The sensitivity to fluorine is 28.0±0.5 mV/lg(p(F 2)), the sensitivity to HF is 44.4±1.6 mV/(p(HF)), and the detection is about 10 ppb in both instances. High temperature silicon carbide sensors can be applied for the determination of fluorine and fluorocarbons (CF 3CH 2F, CF 3CCl 3, CF 3CH 2Cl, CHClF 2, CCl 2F 2, CCl 3F) up to 530°C. The sensor signal for fluorocarbon concentration measurements demonstrates a Nernstian concentration dependence. The detection limit for these gases is ca. 10 ppm.

Separation and preconcentration of fluoride at the ng ml −1 level with a polymer complex of zirconium(IV) followed by potentiometric determination in a flow system

A complex of Zr(IV) with a hydrophilic resin having an iminodiacetic acid group rapidly and selectively adsorbed fluoride from acidic media, which was reversibly expelled on increase in pH. A flow system consisting of a mini-column packed with this polymer complex for separation and preconcentration of fluoride and an ion-selective electrode for detection gave the same peak height for the same amount of fluoride, irrespective of the sample concentration and volume, and thus could be calibrated based on the chemical amount; the detection limit defined by S/ N=3 was 0.1 nmol. Use of the flow system decreased the lower limit for quantitative adsorption of fluoride down to 5×10 −8 M (compared with 1×10 −4 M by batch adsorption), and drastically increased the tolerance limits of interfering cations and anions; even the presence of a fourfold molar ratio of Al 3+ was tolerated with cyclohexane diamine tetraacetic acid as masking reagent. This system was applied to the determination of fluoride in drinking water and concentrated brine. The adsorption and desorption mechanism is discussed in detail.