Determination Of Fluorine Research Articles

Pyrohydrolytic determination of fluorine in coal: A chemometric approach

Corrosion effects in thermal power plants and environmental impact cause an increase in demand for fluorine analysis in coal. Solid sample decomposition, organic and inorganic fluorine compounds, volatility of fluorine species are problems which deserve a special attention. The aim of this work was to optimize the pyrohydrolytic (Phy) determination of fluorine content in the lignite coal. The parameters of pyrohydrolysis were evaluated and optimized by two statistical methods: Plackett–Burman (PB) design and response surface methodology (RSM). The content of fluorine in the absorption solution was measured by fluoride ion-selective electrode. The limit of detection of the proposed method was 20 μg g −1, with good recovery (95%) and relative standard deviation less than 5%. With such benefits as simplicity, precision, accuracy and economy, this method is highly suitable for routine analysis of coal.

Simultaneous Determination of Fluorine, Chlorine, Bromine and Iodine in Six Geochemical Reference Materials Using Pyrohydrolysis, Ion Chromatography and Inductively Coupled Plasma‐Mass Spectrometry

Concentrations of halogens (fluorine, chlorine, bromine and iodine) were determined in six geochemical reference materials (BHVO‐2, GS‐N, JG‐1, JR‐1, JB‐1b, JB‐2). Halogens were first extracted from powdered samples using a pyrohydrolysis technique, then hydrolysis solutions were analysed by ion chromatography for F and Cl and inductively coupled plasma‐mass spectrometry for Br and I. The detection limits in solutions were 100 μg l−1 for both F and Cl and 10 ng l−1 for Br and I. Considering the extraction procedure, performed on a maximum of 500 mg of sample and producing 100 ml of pyrohydrolysis solution, detection limits in rock samples were 20 mg kg−1 for F and Cl and 2 μg kg−1 for Br and I. The mean analytical errors on the studied composition ranges were estimated at 10 mg kg−1 for F and Cl, 100 μg kg−1 for Br and 25 μg kg−1 for I. The concentration values, based on repeated (generally > 10) sample analysis, were in good agreement generally with published values and narrowed the mean dispersion around mean values. Large dispersions are discussed in terms of samples heterogeneity and contaminations during sample preparation. Basaltic RMs were found to be more suitable for studies of halogen compositions than differentiated rock material, especially granites – the powders of which were heterogeneous in halogens at the 500 mg level.

Simultaneous determination of fluorine and iodine in urine by ion chromatography with electrochemical pretreatment

A new method for the simultaneous determination of fluorine and iodine in urine by ion chromatography (IC) with electrochemical pretreatment has been developed. The pretreatment was performed in a novel electrochemical oxidation–neutralization device (EOND), in which iodide of the sample was oxidized to iodate and the alkaline digestion sample solution was neutralized. Under the optimized conditions, the limits of detection (LOD, S/N = 3) were 2.5 μg/L for fluoride and 20 μg/L for iodate, respectively. The recoveries were in the range of 93–102% for fluoride and 86–98% for iodate.

Simultaneous determination of fluorine, chlorine and bromine in cement with ion chromatography after pyrolysis

A rapid method for simultaneous determination of fluorine, chlorine and bromine in cement with ion chromatography after pyrolysis was proposed for routine quality control analysis. The elements were separated from cement sample by pyrolysis, and were subsequently determined with ion chromatograpy. A pyrolysis method was investigated for the separation of micro amounts of these elements from cement. Total time taken to determine these elements is about 45 min including 25 min for the pyrolysis and 18 min for ion chromatography. The results of recovery tests ranged 95% or above. The limits of detection for F, Cl and Br are 0.2, 0.3 and 0.5 mg kg −1, respectively. The method was successfully applied to the simultaneous determination of F, Cl and Br in commercial ordinary Portland cements.

Determination of fluorine in uranium oxyfluoride particles as an indicator of particle age

As swipe samples from enrichment activities typically contain uranium particles with a detectable amount of fluorine, the question was raised whether the analysis of fluorine in particles could complement the information on the uranium isotope ratios. For this, uranium oxyfluoride particles were prepared from the controlled hydrolysis of uranium hexafluoride (UF 6). The relative amount of fluorine was characterized by scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDX), as well as ion-microprobe secondary ion mass spectrometry (IM-SIMS). Of particular interest was the assessment of the reduction of the amount of fluorine over time, and after exposure to UV-light and high temperatures. Micro-Raman spectrometry (MRS) was applied to look for differences in molecular structure between these various sample types. Both SEM-EDX and IM-SIMS showed a general reduction of the fluorine-to-uranium ratio after 1–2 years of storage. The exposure to UV-light and high temperatures was found to have accelerated the loss of fluorine. A distinct peak at 865 cm − 1 Raman shift was detected for the majority of particles analyzed by MRS. For the particles that were heat-treated, the Raman spectra were similar to the spectrum of U 3O 8. Although often large variations were observed between particles from the same sample, the three particle measurement techniques (IM-SIMS, SEM-EDX and MRS) showed some consistent trends. They therefore appear promising in terms of the ability to place bounds on particle age, as well as shedding light on the complex processes involved in UO 2F 2 particle ageing.

Sensitive determination of bromine and iodine in aqueous and biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry using tetramethylammonium hydroxide as a chemical modifier

A procedure for the simultaneous determination of bromine and iodine by inductively coupled plasma (ICP) mass spectrometry was investigated. In order to prevent the decrease in the ionization efficiencies of bromine and iodine atoms caused by the introduction of water mist, electrothermal vaporization was used for sample introduction into the ICP mass spectrometer. To prevent loss of analytes during the drying process, a small amount of tetramethylammonium hydroxide solution was placed as a chemical modifier into the tungsten boat furnace. After evaporation of the solvent, the analytes instantly vaporized and were then introduced into the ICP ion source to detect the (79)Br(+), (81)Br(+), and (127)I(+) ions. By using this system, detection limits of 0.77 pg and 0.086 pg were achieved for bromine and iodine, respectively. These values correspond to 8.1 pg mL(-1) and 0.91 pg mL(-1) of the aqueous bromide and iodide ion concentrations, respectively, for a sampling volume of 95 microL. The relative standard deviations for eight replicate measurements were 2.2% and 2.8% for 20 pg of bromine and 2 pg of iodine, respectively. Approximately 25 batches were vaporizable per hour. The method was successfully applied to the analysis of various certified reference materials and practical situations as biological and aqueous samples. There is further potential for the simultaneous determination of fluorine and chlorine.

Differences of Fluorine in Cements Determined by Photometric Methods after Distillation and Pyrolysis

Using a spectrophotometric method after distillation separation is a standard test method widely employed for the determination of fluorine (F) in cement. Using a flow injection (FI) method after pyrolysis separation for quantification of fluorine in cement has recently been developed. Differences between the fluorine content values obtained by each method have been noted. This paper documents the differences between fluorine content (distillation F) measured spectrophotometrically after distillation and that (pyrolysis F) determined using the FI method after pyrolysis for fourteen commercial Portland cements and identifies a factor contributing to the differences between distillation F and pyrolysis F values. A highly significant relationship existed between distillation F and pyrolysis F values for fourteen cements (r(2) = 0.998, p < 0.001).

Fosfatos com diferentes relações flúor: fósforo na alimentação de frangos de corte

Um experimento foi conduzido com o objetivo de verificar os efeitos de diferentes relações flúor:fosforo na alimentação sobre o desempenho de frangos de corte. Foram utilizados 1.000 pintos de corte de 1 dia distribuídos em um delineamento inteiramente casualizado, com quatro tratamentos e cinco repetições de 50 aves por boxe. Os tratamentos consistiram de quatro fontes de fósforo com relações flúor:fósforo de 1:40, 1:60, 1:80 e 1:100. O experimento foi dividido em três fases experimentais: 1 a 21, 22 a 42 e 43 a 49 dias de idade. Em cada fase, avaliou-se o consumo de ração, o ganho de peso e a conversão alimentar. Ao final do experimento, foram abatidas duas aves de cada repetição para coleta da tíbia e de músculos do peito para análise das concentrações de flúor, cálcio, fósforo e magnésio desses tecidos. As relações flúor:fósforo avaliadas não afetaram o desempenho dos frangos de corte. A deposição óssea de flúor é proporcional à sua concentração na dieta, no entanto, a elevação dos níveis de flúor da dieta não influencia sua deposição nos músculos.

A new approach for fluorine determination by solid sampling graphite furnace molecular absorption spectrometry

This work deals with the determination of fluorine by solid sampling graphite furnace molecular absorption spectrometry. The molecular absorbance of aluminum monofluoride (AlF), which is produced in the vapor phase in the presence of Al 3+, is measured at 227.5 nm, a non-resonant platinum line. A conventional graphite furnace program has been used with pyrolysis and vaporization temperatures of 800 and 2300 °C, respectively. Solutions of Ba 2+ and Al 3+ have been used to avoid fluorine losses during the pyrolysis stage and to produce AlF in the vaporization stage, respectively. Certified coal and alumina samples were analyzed using aqueous standards for calibration. The agreement between the found concentration and the certified value, or the value obtained by another method ranged from 92 to 105%, with a relative standard deviation less than 8.5%. The limit of detection and the characteristic mass was 0.17 μg g − 1 and 205 pg, respectively.

Flow-injection determination of total organic fluorine with off-line defluorination reaction on a solid sorbent bed

Considering recent reports on widespread occurrence and concerns about perfluoroalkyl substances (PFAS) in environmental and biological systems, analysis of these compounds have gained much attention in recent years. Majority of analyte-specific methods are based on a LC/MS/MS or a GC/MS detection, however many environmental or biological studies would benefit from a total organic fluorine (TOF) determination. Presented work was aimed at developing a method for TOF determination. TOF is determined as an amount of inorganic fluoride obtained after defluorination reaction conducted off-line using sodium biphenyl reagent directly on the sorbent without elution of retained analytes. Recovered fluoride was analyzed using flow-injection system with either fluorimetric or potentiometric detection. The TOF method was tested using perfluorocarboxylic acids (PFCA), including perfluorooctanoic acid (PFOA), as model compounds. Considering low concentrations of PFAS in natural samples, solid-phase extraction as a preconcentration procedure was evaluated. Several carbon-based sorbents were tested, namely multi-wall carbon nanotubes, carbon nanofibres and activated carbon. Good sorption of all analytes was achieved and defluorination reaction was possible to carry out directly on a sorbent bed. Recoveries obtained for PFCAs, adsorbed on an activated carbon sorbent, and measured as TOF, were 99.5 ± 1.7, 110 ± 9.4, 95 ± 26, 120 ± 32, 110 ± 12 for C4, C6, C8, C10 and C12-PFCA, respectively. Two flow systems that would enable the defluorination reaction and fluoride determination in a single system were designed and tested.

Application of prompt activation analysis in the determination of fluorine in tea, in international geochemical standards, bones and teeth of experimental animals

By making use of the 19F(p,αγ)16O reaction the F-concentrations of different varieties of tea leaves, of some international geochemical reference materials, and of the bones and teeth of some experimental animals have been determined. The tea leaves from Ceylon (ordinary), Orange Pekoe (special Ceylon), China (ordinary black), Lapsang Souchong (special smoked Chinese) and Darjeeling (India) were found to contain 170 ppm, 170 ppm, 120 ppm, 160 ppm and 100 ppm of fluorine, respectively, The F-concentrations of established geochemical reference materials, NIM-D, NIM-N, NIM-P and NIM-S, from the National Institute of Metallurgy, South Africa were determined to be 60 ppm, 120 ppm, 130 ppm and 190 ppm, respectively. The bones of rabbits, who were given fluoridated water, were found to contain much higher amount of fluorine than the bones of the control rabbit. Furthermore, the rabbits who were kept on fluoridated water for 45 days, had almost double the amount of F in their bones than the rabbits who were given fluoridated water for only 15 days. Similarly, the teeth of grown-up monkeys who were given fluoridated water since birth had double the amount of fluorine than those of the control monkey.

Direct spectrometric determination of total fluorine in geological materials by continuous powder introduction into helium microwave induced plasma

A sensitive, direct, spectrometric method for the determination of total fluorine content in a wide variety of geological materials has been developed. Solid samples were ground in a mill and sieved prior to continuous powder introduction microwave induced plasma optical emission spectrometry (CPI-MIP-OES) determination with a helium plasma. The effects of operating conditions and sample particle size on the analytical signal were evaluated. Materials were introduced as a solid–gas aerosol. The amount of fluorine was measured using calibration standards prepared by dropping of a standard fluoride solution on a suitable powdered support (silica or activated carbon) with matrix matching. The experimental detection limit for fluorine at line 685.6 nm, obtained with the CPI-He-MIP-OES method, was of the order of 3–6 μg g−1; the uncertainty was about 5–17%. The developed method was validated by carrying out the analysis of different certified reference materials including soils, fly ash and coals.

Determination of trace levels of total fluorine in water using combustion ion chromatography for fluorine: A mass balance approach to determine individual perfluorinated chemicals in water

Perfluorinated compounds (PFCs) such as perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) have received worldwide attention because of their environmental persistence and widespread distribution. Because of the lack of robust analytical methods and standards to detect all of the PFCs, and their precursors and metabolic intermediates, a mass balance approach involving the determination of total fluorine (TF), followed by fractionation of samples to separately determine inorganic and organic fluorine, is needed. In this study, we have developed a method to determine low μg/L levels of total fluorine (TF) in seawater samples. Further, seawater samples were fractionated into organic and inorganic fractions by extraction with organic solvents, which were then analyzed for TF, extractable organic fluorine (EOF) and inorganic fluorine (IF; i.e., fluoride). Concentrations of known perfluorinated compounds (PFCs) including PFOS and PFOA were also determined in water samples by liquid chromatography–tandem mass spectrometry (LC–MS/MS) to enable calculation of the fraction of fluorine that is contributed by PFCs to TF. A major proportion of fluorine in seawater was in the form of fluoride (>90% in locations not affected by direct discharges). Nevertheless, within the organofluorine fraction, a major percentage (60–90%) of fluorine still remains unknown in water samples, suggesting the occurrence of other fluorinated acids in addition to known perfluorinated acids. Further studies are needed to identify and quantify the unidentified organofluorines in seawater. Mass balance analysis of total organic fluorine (TOF) and EOF is important, if we are to understand transport and fate of fluorinated compounds in the environment, and if we are to identify the sources of unidentified fluorinated compounds.

Determination of total fluorine in coal by use of oxygen flask combustion method with catalyst

A rapid and convenient analytical method has been developed for the determination of total F in coal by use of oxygen flask combustion (OFC) method with catalyst. Coal was combusted with excessive oxygen in a quartz flask and the resulting gas was absorbed in water, and the fluoride ion in the solution was determined with a fluoride-ion selective electrode (F-ISE). Seven certified reference materials of coal were tested. The effects of the repetition of OFC procedure, the use of catalyst, and the particle size of coal were investigated. The F concentrations in these coals determined by the proposed method gave good recoveries for their certified or reference values. The use of proper catalyst was necessary especially when coals of high F concentrations (above ca. 150 μg g −1) were analyzed. For the catalyst, the combined use of WO 3 and Sn was the most efficient, and the mechanism was studied. Twenty brands of Japanese standard coals (SS coals) were analyzed by the present method, and the data were compared to those obtained from the pyrohydrolysis method.

Ion Chromatographic Determination of Fluorine and Chlorine in Silicate Rocks Following Alkaline Fusion

A simple and accurate method to determine fluorine and chlorine contents in small amounts (∼ 30 mg) in rock has been developed using ion chromatography after extraction by alkaline fusion. Powdered sample was mixed with sodium carbonate and zinc oxide at a mass ratio of 1:3:1, and was fused in an electric furnace at 900 °C for 30-40 minutes. An aqueous solution obtained by dissolving the fused silicate rock was diluted to the appropriate concentration of sodium carbonate (< ∼ 24 mmol l-1) to minimise the tailing effect on F- during ion chromatography caused by the large amount of carbonate species originating from the flux. Fluorine and chlorine contents were then determined by a standard additions method. Based on the relative standard deviation of the backgrounds, detection limits of both fluorine and chlorine were ∼ 4 μg g-1, when 30 mg test portions were fused and diluted by a factor of 1200. We also report new fluorine and chlorine contents in nine GSJ (Geological Survey of Japan) reference materials, including peridotite (JP-1), granite (JG-1a), basalts (JB-1b, 2 and 3), andesites (JA-1 and 2) and rhyolites (JR-1 and 2). Fluorine and chlorine contents in the reference materials in this study were consistent with previously reported values. Reproducibilities were < 10 % for samples with F and Cl concentrations of > 20 μg g-1 and < 20 % with F and Cl < 20 μg g-1. Une méthode simple et précise de détermination des concentrations en chlore et fluore dans des petits échantillons (∼ 30 mg) de roches a été développée, basée sur l'utilisation de la chromatographie ionique après extraction par fusion alcaline. l'échantillon en poudre est mélangé avec du carbonate de sodium et de l'oxyde de zinc dans un rapport massique de 1 :3 :1 et est fondu dans un four électrique à 900 °C pendant 30-40 minutes. La solution aqueuse obtenue par dissolution du verre de fusion est diluée à une concentration de carbonate de sodium qui permette de minimiser les effets de queue sur F durant la chromatographie ionique, effet causé par la grande quantité d'espèces de carbonates provenant du fondant. Les teneurs en fluore et chlore sont alors déterminées par la méthode de l'addition de standards. A partir des écarts types relatives des bruits de fond, les limites de détection pour le fluor et le chlore ont été estimées à∼ 4 μg g-1, pour un échantillon test de 30 mg fondu puis dilué d'un facteur 1200. Nous présentons aussi de nouvelles mesures de concentrations en chlore et fluor dans neuf matériaux de référence du GSJ (Service Géologique du Japon): la péridotite (JP-1), le granite (JG-1a), les basaltes (JB-1b, 2 et 3), les andésites (JA-1 et 2), les rhyolites (JR-1 et 2). Les teneurs en fluor et en chlore de ces matériaux se sont révélées être en accord avec les valeurs reportées précédemment. Les reproductibilités sont < 10% pour des échantillons ayant des concentrations supérieures à 20 μg g-1 et < 20% pour des teneurs de F et Cl < 20 μg g-1.

Determination of halogens via molecules in the air–acetylene flame using high-resolution continuum source absorption spectrometry: Part I. Fluorine

The particular capabilities of a high-resolution continuum source absorption spectrometer were exploited to the determination of halogens in an ordinary air–acetylene flame. In the first part of the studies, a simple method was developed, which allows the determination of fluorine by measuring GaF molecular absorption. The molecules are generated in the presence of an excess of Ga in the flame. Under such conditions, all fluorine is converted into GaF, yielding an evaluable signal for the fluorine determination. Molecular bands of GaF were found between 211 and 214 nm; the strongest absorption band head at 211.248 nm was examined in detail to prove its applicability to analytical measurements. To this end, potential chemical and spectral interferences were tested, using various highly concentrated acids and metallic salt solutions. Since no serious interferences were found, the new method proved to be very reliable. As limit of detection, 1 mg L − 1 fluorine in the presence of 10 g L − 1 Ga was achieved, using a measurement time of five seconds. The linear dynamic range covers more than three orders of magnitude. Accuracy and precision were verified by analysis of a standard reference material (BCR No. 33).

Behavior of fluorine and chlorine in volcanic ash of Sakurajima volcano, Japan in the sequence of its eruptive activity

Abstract At Sakurajima volcano, strombolian eruptions forerun vulcanian explosions, and volcanian explosions are often followed by continuous ash eruptions. Change in the mode of its eruptive activity is drastic and release of volatiles from magma corresponding to its eruptive activity is examined by determination of fluorine and chlorine in volcanic ash. The F contents of all the ash samples are markedly higher than the arithmetic mean value of Japanese volcanic rocks (ca. 300 μg/g). Further, the water-soluble Cl contents of almost all the ash samples are also extremely higher than those of Japanese volcanic rocks (less than 50 μg/g). This is attributed to fixation of F and Cl in hot gas onto the volcanic ash particles in the crater and/or eruption plumes. The differences in those contents among the “strombolian eruption”-, “vulcanian explosion”- and “continuous ash eruption” groups are significant, which implies that hot gas rich in F and Cl are issued during strombolian eruptions, while those halogens are less concentrated in hot gas after strombolian eruptions. The water-insoluble Cl content of the “strombolian eruption” group is significantly higher than those of the other groups. This result implies that Cl and the other volatiles are intensely released from magma during the doming period before vulcanian eruptions. Yet, it is inferred that continuous ash eruption is the final phase of vulcanian one.

Determination of non-metals via molecular absorption using high-resolution continuum source absorption spectrometry and graphite furnace atomization

This work describes investigations on the determination of the non-metals fluorine, chlorine, sulfur and phosphorus in a graphite furnace atomizer using high-resolution continuum source absorption spectrometry. With this technique, the general problem of limited accessibility to the non-metal resonance lines, all located in the vacuum ultraviolet wavelength region, could be avoided by evaluation of narrow-band molecular absorption in the ultraviolet spectral region. The absorption originates from diatomic molecules produced under certain conditions in the graphite atomizer in the presence of the element in question. In detail, an excess of the metals gallium and aluminium was used to convert fluorine and chlorine to their molecular forms GaF and AlCl, respectively. In a similar manner, sulfur could be converted to CS and phosphorus to PO molecules. For all species, narrow spectral structures, belonging to specific band heads or individual rotational lines, could be found at well-accessible wavelengths between 211 and 261 nm. Using these absorption structures, analytical parameters were evaluated for the determination of the four non-metals. The obtained values for the characteristic masses and the limits of detection are as follows: 13 pg and 9 pg for fluorine; 300 pg and 70 pg for chlorine; 12 ng and 2.3 ng for sulfur; 4.4 ng and 0.9 ng for phosphorus. All methods developed were confirmed by measurements on certified reference materials. In comparison to previous investigations with an air–acetylene flame system, an improvement of up to three orders of magnitude in the limits of detection was achieved.

Chemical analysis of phosphate rock using different methods—advantages and disadvantages

Many analytical methods are considered for chemical analysis of phosphate rock because the accuracy of analysis is very important. In the present investigations, spectrophotometric and x-ray spectrometric methods were used to determine P2O5 whereas SiO2, CaO, MgO, Al2O3 and Fe2O3 were determined by gravimetric and x-ray spectrometric methods. Volumetric and x-ray spectrometry methods are necessary for fluorine determination. The investigations revealed that x-ray spectrometry is a precise and accurate technique, which is cost effective and so better than other methods. Spectrophotometric, volumetric and gravimetric methods are expensive, time consuming and laborious. X-ray spectrometry is suggested for commercial companies using regular analyses to save chemicals, time and labour and to maintain quality. Copyright © 2006 John Wiley & Sons, Ltd.

Improvements in the Determination of Fluorine in Fuel and Lubricants by Oxidative Combustion and Ion-Selective Electrode Detection

Abstract Oxidative combustion combined with ion-selective electrode detection is one of several techniques available for the analysis of fluorine in fuels and lubricants to the petroleum and petrochemical industry. This technique was first developed in the mid-1990s to provide an alternative to the widely used Wickbold method, which is very time consuming and extremely hazardous. The early designs were marginally successful due to the lack of sensitivity and stability, the use of large volumes of solvents, inconsistent delivery of fluids, plugging of catch and hold valves, numerous sources of contamination, and long analysis times. The design has been refined to enhance the sensitivity, stability, and accuracy of the fluoride determination. Enhancements include improved ion-specific electrodes with increased sensitivity, the use of circulating baths to stabilize temperature fluctuations, improved sample introduction and flow systems, and redesigned electronic circuitry.