Total Fluorine Content Research Articles

Fluorine in the rocks and sediments of volcanic areas in central Italy: total content, enrichment and leaching processes and a hypothesis on the vulnerability of the related aquifers

Rock, sediment and water samples from areas characterised by hydrothermal alterations in the Sabatini and Vico Volcanic Districts, near Rome and the large city of Viterbo, respectively, were collected and analysed to determine the total fluorine (F) content and to understand the F geochemical background level in the volcanic districts of central Italy. Leaching and alteration processes controlling the high concentration of F in water were also investigated. Fluorine concentrations were directly determined (potentiometrically) by an F selective electrode in water samples, while the procedure for rock samples included preliminary F dissolution through alkaline fusion. F concentrations higher than 800 mg kg(-1) were commonly found in the analysed rocks and sediments; the concentration depended on the lithology and on the distance from the alteration areas. A specific successive sampling campaign was conducted in three areas where the F content in sediments was particularly high; in the same areas, measurements of CO(2) flux were also performed to investigate the possible deep origin of F. To verify the relationships among the high F contents in rocks and sediments, the leaching processes involved and the presence of F in the aquifer, we also collected water samples in the western sector of the Sabatini Volcanic District, where hydrothermal manifestations and mineral springs are common. The data were processed using a GIS system in which the F distribution was combined with morphological and geological observations. The main results of our study are that (1) F concentrations are higher in volcanic and recently formed travertine (especially in hydrothermally altered sediments) than in sedimentary rocks and decrease with distance from hydrothermal alteration areas, (2) F is more easily leached from hydrothermally altered rocks and from travertine and (3) sediments enriched with F may indicate the presence of deep regional fractures that represent direct pathways of hydrothermal fluids from the crust to the surface.

Potential release of hydrogen fluoride from domestic coal in endemic fluorosis area in Guizhou, China

Almost half of the total rural area of Guizhou Province and many regions within the 11 adjacent provinces in southwestern China have a long history (at least 70 years) of endemic fluorosis, including dental fluorosis and osteofluorosis along with its associated deformities and disabilities. Over decades of research, this specific type of endemic fluorosis has been defined as coal-burning fluorosis, which is distinct from drinking-water fluorosis. It is generally acknowledged that indoor burning and combustion of high-fluorine coal leads to food contamination, and fluorine then enters the human body. However, the exact chemical form of fluorine during its release and transfer to the body is still unknown. In the present study, 21 domestic coal samples from outcrop and semi-outcrop coal collected in five villages with fluorosis were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The total mass fraction of sulfur in the samples ranged from 0.24%–5.58% and total fluorine content ranged 90.2–149.2 mg/kg. H3O+, H2SO 4 + and HSO 4 − were detected in the samples by TOF-SIMS, which indicated that sulfuric acid hydrate (H2SO4·H2O) was present in the samples. F− was detected in all of these, which suggested the samples contain ionic fluorine compounds. Under certain circumstances, such as heating or burning, the prevalence and coexistence of the acid (H2SO4·H2O) and base (F−) would lead to a neutralization reaction producing volatile hydrogen fluoride (HF, bp = 19.5°C). This would be the chemical form of fluorine released from the coal. Further studies using HF and SO2 test tubes on headspace gas over coal samples heated to 200°C in the laboratory and on headspace gas over stoves or chimney tops at rural residences confirmed the release of HF.

Rapid quantification of inflammation in tissue samples using perfluorocarbon emulsion and fluorine-19 nuclear magnetic resonance.

Quantification of inflammation in tissue samples can be a time-intensive bottleneck in therapeutic discovery and preclinical endeavors. We describe a versatile and rapid approach to quantitatively assay macrophage burden in intact tissue samples. Perfluorocarbon (PFC) emulsion is injected intravenously, and the emulsion droplets are effectively taken up by monocytes and macrophages. These 'in situ' labeled cells participate in inflammatory events in vivo resulting in PFC accumulation at inflammatory loci. Necropsied tissues or intact organs are subjected to conventional fluorine-19 ((19)F) NMR spectroscopy to quantify the total fluorine content per sample, proportional to the macrophage burden. We applied these methods to a rat model of experimental allergic encephalomyelitis (EAE) exhibiting extensive inflammation and demyelination in the central nervous system (CNS), particularly in the spinal cord. In a cohort of EAE rats, we used (19)F NMR to derive an inflammation index (IFI) in intact CNS tissues. Immunohistochemistry was used to confirm intracellular colocalization of the PFC droplets within CNS CD68+ cells having macrophage morphology. The IFI linearly correlated to mRNA levels of CD68 via real-time PCR analysis. This (19)F NMR approach can accelerate tissue analysis by at least an order of magnitude compared with histological approaches.

A fast and accurate method for the determination of total and soluble fluorine in toothpaste using high-resolution graphite furnace molecular absorption spectrometry and its comparison with established techniques

A fast and reliable method has been developed for the determination of total and soluble fluorine in toothpaste, important quality control parameters in dentifrices. The method is based on the molecular absorption of gallium mono-fluoride, GaF, using a commercially available high-resolution continuum source atomic absorption spectrometer. Transversely heated platform tubes with zirconium as permanent chemical modifier were used throughout. Before each sample injection, a palladium and zirconium modifier solution and a gallium reagent were deposited onto the graphite platform and thermally pretreated to transform them into their active forms. The samples were only diluted and introduced directly into the graphite tube together with additional gallium reagent. Under these conditions the fluoride was stable up to a pyrolysis temperature of 550 °C, and the optimum vaporization (molecule formation) temperature was 1550 °C. The GaF molecular absorption was measured at 211.248 nm, and the limits of detection and quantification were 5.2 pg and 17 pg, respectively, corresponding to a limit of quantification of about 30 μg g −1 (ppm) F in the original toothpaste. The proposed method was used for the determination of total and soluble fluorine content in toothpaste samples from different manufactures. The samples contained different ionic fluoride species and sodium monofluorophosphate (MFP) with covalently bonded fluorine. The results for total fluorine were compared with those obtained with a modified conventional headspace gas chromatographic procedure. Accuracy and precision of the two procedures were comparable, but the proposed procedure was much less labor-intensive, and about five times faster than the latter one.

Comparison of total fluorine, extractable organic fluorine and perfluorinated compounds in the blood of wild and pefluorooctanoate (PFOA)-exposed rats: Evidence for the presence of other organofluorine compounds

The widespread occurrence and environmental persistence of perfluorinated compounds (PFCs) received worldwide attention recently. Exhaustive analysis of all fluorinated compounds in an environmental sample can be daunting because of the constraints in the availability of analytical standards and extraction methods. Combustion ion chromatographic technique for trace fluorine analysis was used to assess the concentrations of known PFCs (e.g., PFOS, PFOA) and total fluorine (TF) in the blood of wild rats collected from Japan. The technique was further validated using tissues from PFOA-exposed rats. Six PFCs (PFOS, PFOSA, PFUnDA, PFDA, PFNA, and PFOA) were detected in all of the wild rat blood samples. Concentrations of extractable organic fluorine (EOF) in fraction 1 (Fr1; MTBE extraction) of wild rats ranged 60.9–134 ng F mL −1, while those in fraction 2 (Fr2; hexane) were below LOQ (32 ng F mL −1); TF concentrations in the blood of wild rats ranged from 59.9–192 ng F mL −1. The contribution of known PFCs in EOF-Fr1 (MTBE) varied from 9% to 89% (56% on average), and known PFC concentrations in TF content were less than 25%. In contrast, TF concentrations in the blood of PFOA-exposed rats ranged from 46900 to 111000 ng F mL −1, with PFOA contributing over 90% of TF. A comparison of results from the samples analyzed in this study and the literature revealed three distinct groups with PFOA/known PFC and TF levels (i.e., wild rats and general population, occupationally exposed workers, and PFOA-exposed laboratory rats). The mass balance analysis of the different forms of fluorine in blood suggested the presence of other forms of organic fluorine in addition to known PFCs.

Properties of low surface energy fluorocarbon polymers with fluoro-acrylic resins

The low surface energy fluorocarbon polymer from the synthesized fluoro-acrylic resins was developed. Then the molecule orientation principle of nonpolar and polar functional groups in the polymers was analyzed. And the contact angles of pure water drops on the surfaces of various fluoro-monomer homopolymers and interpolymers were measured. So the relation of polymers’ fluoro-content with the surface energy was determined. The distribution of fluoric functional groups in the polymers was investigated. And the test results show that though the total fluorine content of the fluorocarbon polymers is relative few, their surface energy is really low due to the enrichment of fluoro-chains on the polymers surface.

Fluorine speciation in topsoils of three active volcanoes of Sicily (Italy)

Fluorine is one of the many environmental harmful elements released by volcanic activity. The content of total oxalate-extractable and water-extractable fluorine was determined in 96 topsoils of three active volcanic systems of southern Italy (Mt Etna, Stromboli and Vulcano). Total fluorine (F) content (FTOT) ranges from 112 to 7,430 mg kg−1, F extracted with oxalate (FOX) ranges from 16 to 2,320 mg kg−1 (2–93% of FTOT) and F extracted with distilled water ( \( F_{{{\text{H}}_{{\text{2}}} {\text{O}}}} \)) ranges from 1.7 to 159 mg kg−1 (0.2–40 % of FTOT). Fluorine in the sampled topsoils derives both from the weathering of volcanic rocks and ashes and from the enhanced deposition due to volcanic gas emissions either from open-conduit passive degassing (Mt Etna and Stromboli) or from a fumarolic field (Vulcano). Fluorine accumulation in the studied soils does not generally present particular environmental issues except for a few anomalous sites at Vulcano, where measured contents could be dangerous both for vegetation and for grazing animals.

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.

Laser and Physical Properties of BODIPY Chromophores in New Fluorinated Polymeric Materials

We report on the synthesis and photophysical and lasing properties of new linear and cross-linked fluorinated polymeric materials doped with two BODIPY chromophores such as PM567 and PM597. The total fluorine content of the matrixes was varied adding to methyl methacrylate (MMA) different volumetric proportions of monomers with increased number of fluorine atoms: 2,2,2-trifluoromethyl methacrylate, 2,2,3,3,3,-pentafluoropropyl methacrylate (PFMA), and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate. The rigidity of the materials was modified adding to PFMA di-, tri-, and tetra-functionalized comonomers such as ethyleneglycol dimethacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate. When the fluorine-modified organic matrixes were transversally pumped at 532 nm, highly stable laser operation with high, not-optimized efficiencies up to 42% was obtained. The highest photostability was recorded for PM597 doped MMA/PFMA 70/30 linear matrix, with no sign of degradation in the laser output aft...

Structural forms of fluorides in bone tissue of animals under chronic fluoride intoxication

High-resolution solid-state 19F NMR method has been used to examine the chemical structural forms of fluorine introduced into the bone tissue of experimental animals (Vistar rats) exposed to 30 day fluoride inhalation. It is shown that in the bone tissue three structural forms of fluorides are deposited: a solid phase of F-apatite and mobile nanoparticles of CaF2 and MgF2 (or KMgF3) with the ratio of fluorine concentration in these three forms ∼2:2:1. During the following 30 day rehabilitation this ratio remains constant, the total fluorine content in the bone tissue decreases ∼3 times and the F-apatite phase transforms into disordered (F, OH)-apatite. A protective effect of the zeolitic enterosorbent (klinoptilolite) on fluorine binding in the intoxication process was found, as well as the promotional effect of this enterosorbent on fluorine excretion during the postfluoride rehabilitation.

Depth profiling of latex blends of fluorinated and fluorine‐free acrylates with laser‐induced secondary mass spectrometry

AbstractWe explored phase separation and self‐assembly of perfluoroalkyl segments at the surface of polymer films obtained from latices of semifluorinated acrylate copolymers and the corresponding latex blends of nonfluorinated and semifluorinated polyacrylates. With laser‐induced secondary mass spectrometry the fluorine distribution was measured after annealing above the minimum film‐forming temperature of the polymers up to a depth of several micrometers. Depth profiles of a semifluorinated acrylate homopolymer and latex blends thereof with fluorine‐free alkylacrylates with 25, 50, and 75 mol % semifluorinated acrylate as well as a copolymer comprised of alkyl acrylate and semifluorinated acrylate (50/50 mol %) were investigated. In the case of latex blends containing both semifluorinated polyacrylates and fluorine‐free or low‐fluorine polymers, self‐assembly accounted for enrichment of the perfluoroalkyl segments at the surface. Coatings exhibiting low surface energy and having a substantially reduced total fluorine content were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 360–367, 2003

Plasma assisted surface coating of porous solids

Surface modification of high-porosity solids using RF plasma has been investigated. Hydrophobic coatings were deposited on a stack of five porous filter papers using four types of plasma from different fluorine-containing monomers (TDFO, PDFOA, PFDD and PFMCH). Surface chemistry and water contact angles of each layer were analyzed using X-ray photoelectron spectroscopy (XPS) and video contact angle (VCA) measurements. It is seen that CF 2 and CF 3 groups are responsible for hydrophobic behavior and contact angle values correlates very well with total surface fluorine content. As the average surface fluorine concentration increases to about 15%, the surface becomes abruptly hydrophobic. This study indicates that a very thin coating (average thickness smaller than 1–2 nm) is needed for hydrophobic behavior. Additional deposition increases coating thickness, but has no effect on contact angle. All the monomers are equally effective in coating the “external” surfaces of the stack, but the extent of permeation of the plasma into the inner layers varies with monomer structure. PDFOA produces more penetrating plasma compared to other molecules. The molar ratio of the two hydrophobic functional groups (CF 2/CF 3) in all coatings is lower than that in the original monomer due to molecular fragmentation in the plasma. In the straight chain monomers studied, CF 2/CF 3 ratio of the coating follows the same trend as in the starting molecule. However, in the cyclic monomer studied, this ratio is significantly lower indicating greater fragmentation of such molecules. These results indicate that plasma-induced coatings can modify surface properties of high-porosity materials and that the extent of permeation can be controlled.

Analysis of the role of fluorine content on the thermal stability of a-C:H:F thin films

The effect of fluorine incorporation on the thermal stability of hydrogenated amorphous carbon (a-C:H) films was investigated by Raman spectroscopy, infrared (IR) absorption, X-ray photoelectron spectroscopy (XPS), as well as measurements of the film thickness. Results of IR and XPS analysis suggest that the total fluorine content after annealing corresponds to the amount of fluorine bonded to carbon in the as-deposited films. The evolution of Raman spectra obtained on films before annealing indicates that progressive fluorine incorporation is accompanied by graphitisation. In particular, the decrease in the optical bandgap is interpreted as a clustering of the existing sp2 carbon sites. Under thermal annealing, the film structures are very stable and the films do not show any change in refractive index values with respect to the original as-deposited films, for all fluorine contents. This behaviour is most likely due to extended graphitisation, with no sp2 clustering. The experimental findings suggest that the strength of the CF bonding configuration promotes thermal stability of the films.

Fluorine content in soils of Northern Pomoravlje

Soil sampling was carried out in the Velika Morava river valley, covering the area from Velika Plana to the mouth of Morava to the Danube. The composite soil samples, representing alluvial soils (22 samples), cambisols (14) and smonitzas (4), were taken from plough layers, based on a regular square grid with intervals set at 5x5 km, covering total area of 100,000 ha. The total and available fluorine contents were determined in the soils samples. The highest average amount of total fluorine was found for alluvial soils (391 mg kg-1), then for smonitzas (348 mg kg-1) and the lowest one for cambisols (285 mg kg-1). These amounts are within normal fluorine content for soils (150-400 mg kg-1), although the maximum found levels were even about 500 mg kg-1. The available fluorine content was very low (< 1 mg kg-1), being mostly less than 0.2 % from its total amount, so it could be concluded that there was no danger from fluorine accumulation in the plants. Statistically significant correlation coefficient between total and available fluorine contents was not obtained. The total and available fluorine contents have mostly been in the correlation (with positive sign) with soil pH and the content of mechanical fraction silt+clay. Significant correlation coefficients between total fluorine content and the content of some heavy metals (Cr, Ni, Co, Cu, As) were also found, which indicated their mutual geochemical origin.

Part 3. Copolymers of 1H,1H,2H,2H‐perfluorodecyl acrylate and 2,2,2‐trifluoroethyl methacrylate with butyl methacrylate

AbstractCopolymers of 2,2,2‐trifluoroethyl methacrylate, or 1H,1H,2H,2H‐perfluorodecyl acrylate (XFDA) and butyl methacrylate (BMA) have been irradiated in air under artificial solar light and their photo‐oxidative stability has been investigated. Molecular and chemical changes occurring during the treatments have been monitored by weight loss and gel content determination, size exclusion chromatography and FTIR spectroscopy. It has been determined that the overall behaviour of both copolymers is controlled by the BMA units, independently of the total fluorine content. The photo‐ageing takes place mainly via the mechanism of oxidation of methacrylic polymers containing long side ester groups, whose flexibility favours macroradical coupling reactions. The tendency to crosslink is balanced only in the case of the initial stages of degradation of XFDA/BMA by the scission reactions derived from the direct attack of oxygen on the fluorinated acrylic units.© 2001 Society of Chemical Industry

SeF 4 and SF 4 fluorination of BPL activated carbon surfaces

Fluorination of the surfaces of activated carbons has been proposed as a method to enhance the resistance of the activated carbon to the unwanted adsorption of water. In addition, the fluorination would increase the efficiency of the activated carbon to adsorb hydrophobic compounds. This study details the fluorination of BPL activated carbon with two selective fluorinating agents, selenium tetrafluoride (SeF 4) and sulfur tetrafluoride (SF 4). SeF 4 and SF 4 have been used previously to replace oxygen atoms with fluorine atoms. The BPL activated carbon was oxidized with nitric acid to increase the number of surface oxides present on the activated carbon. These surface oxides were the intended targets for the SeF 4 and SF 4 fluorinations. Results presented in this report include the reaction procedures used and the elemental chemical analysis of the products. Total fluorine content of the products and changes in the atomic percentages of carbon and oxygen from before the fluorination reactions to after reactions were completed are reported. Also, results of water uptake, surface acidity and surface area analysis studies are provided.

Compositional and sequential analysis of poly(ethylene-tetrafluoroethylene) by pyrolysis-gas chromatography

Compositional and sequential analysis of PETFE (poly(ethylene (E)-tetrafluoro-ethylene (TFE)-perfluoroalkylethylene (RfCHCH 2))) are carried out after optimization of pyrolysis-gas chromatography (Py-GC) experimental conditions. The content of RfCHCH 2 is readily obtained by Py-GC using standard samples whose compositions are known by conventional techniques ( 19F NMR and total fluorine content analysis). Reproducibility of the determination of each composition by Py-GC stands up to comparison with the conventional techniques. The amount of TFE-TFE sequence in the terpolymer is estimated from seven selected peaks on the pyrogram, so that a rough indication of the TFE E ratio is obtained. Consequently, a quick and easy determination method by Py-GC is established. Furthermore, it is found that crystallinity due to the decrease in the alternating character of the TFE-E sequence may cause the decrease in melting point of the terpolymer.

Foam concentration measurement techniques

Three types of foam concentration measurement techniques are examined: total fluorine content, optical absorption, and specific conductivity. Specific conductivity was found to be the most useful for field measurements and was therefore compared with the traditional refractive index approach. It was found that electrical conductance provides a more accurate method of estimating the concentration of AFFF solution than does the refractive index technique described in NFPA 11.

Measurement of fluorine total concentration in dental enamel using fast-neutron activation

Fluorine which is present in dental enamel, at the level of a few tens to a few hundred ppm, plays an important role in the behaviour of this tissue. Therefore its quantitative determination is of interest for particular studies of the dental system. We present a nuclear nondestructive method to determine the total fluorine content in dental enamel by cyclotron-produced fast-neutron activation. The 19F(n, 2n) reaction leads to 18F which is a β + emitter with a 109.8 min half-life. The irradiated sample activity is measured by detecting in coincidence the annihilation photons. A fluorine standard is used for calibration. The detection limit is of the order of 1 ppm, while the reproducibility is better than 95%.

Fluorine redistribution in a chemical vapor deposited tungsten/polycrystalline silicon gate structure during heat treatment

Fluorine redistribution during heat treatment of chemical vapor deposited tungsten/polycrystalline silicon gate structures was analyzed by the nuclear resonance broadening technique. The tungsten layer was deposited from a hydrogen/tungsten hexafluoride gas mixture. Upon heat treatment in the temperature range 1020–1325-K tungsten disilicide formation was observed using Rutherford backscattering spectrometry. In the as-deposited sample, the fluorine was accumulated at the tungsten/polycrystalline silicon interface. After silicide formation the fluorine was observed at the tungsten disilicide/polycrystalline silicon interface. At temperatures above 1120 K fluorine starts to diffuse through the polycrystalline silicon layer. A variation in the total fluorine content between the samples was also observed. The origin of the fluorine redistribution as well as the variation in the total fluorine content is discussed in connection to conceivable mechanisms.