Comparison of extraction methods for per- and polyfluoroalkyl substances (PFAS) in human serum and placenta samples-insights into extractable organic fluorine (EOF).

Since the detection of per- and polyfluoroalkyl substances (PFAS) in humans and different environmental media in the last two decades, this substance group has attracted a lot of attention as well as increasing concerns. The fluorine mass balance approach, by comparing the levels of targeted PFAS after conversion to fluorine equivalents with those of extractable organic fluorine (EOF), showed the presence of unidentified organofluorine in different environmental samples. Out of the thousands of PFAS in existence, only a very small fraction is included in routine analysis. In recent years, liquid chromatography coupled with tandem-mass spectrometry (LC-MS/MS) has demonstrated the ability to analytically cover a wide spectrum of PFAS. In contrast, conventional extraction methods developed 10 to 15 years ago were only evaluated for a limited number of PFAS. The aim of the present study was to evaluate the advantages and disadvantages of three different extraction methods, adapted from the literatures without further optimization (ion-pair liquid-liquid extraction, solid-phase extraction (SPE), using hydrophilic-lipophilic (HLB) or weak anion exchange (WAX) sorbents), for human biomonitoring of 61 PFAS in serum and placental tissue samples. In addition, levels of EOF were compared among these extraction methods via spiked samples. Results showed that performance, in terms of recovery, differed between the extraction methods for different PFAS; different extraction methods resulted in different EOF concentrations indicating that the choice of extraction method is important for target PFAS and EOF analysis. Results of maternal serum samples, analyzed in two different laboratories using two different extraction methods, showed an accordance of 107.6% (± 21.3); the detected perfluoroalkyl acids (PFAAs) in maternal and cord serum samples were in the range of 0.076 to 2.9 ng/mL.Graphical abstract.

Photocatalytic defluorination of perfluorooctanoic acid by surface defective BiOCl: Fast microwave solvothermal synthesis and photocatalytic mechanisms.

There is an urgent need for developing cost-effective methods for the treatment of perfluorooctanoic acid (PFOA) due to its global emergence and potential risks. In this study, taking surface-defective BiOCl as an example, a strategy of surface oxygen vacancy modulation was used to promote the photocatalytic defluorination efficiency of PFOA under simulated sunlight irradiation. The defective BiOCl was fabricated by a fast microwave solvothermal method, which was found to induce more surface oxygen vacancies than conventional solvothermal and precipitation methods. As a result, the as-prepared BiOCl showed significantly enhanced defluorination efficiency, which was 2.7 and 33.8 times higher than that of BiOCl fabricated by conventional solvothermal and precipitation methods, respectively. Mechanistic studies indicated that the defluorination of PFOA follows a direct hole (h+) oxidation pathway with the aid of •OH, while the oxygen vacancies not only promote charge separation but also facilitate the intimate contact between the photocatalyst surface and PFOA by coordinating with its terminal carboxylate group in a bidentate or bridging mode. This work will provide a general strategy of oxygen vacancy modulation by microwave-assisted methods for efficient photocatalytic defluorination of PFOA in the environment using sunlight as the energy source.

Targeted expression and purification of fluorine labelled cold shock protein B by using an auxotrophic strategy.

High resolution NMR spectroscopy is a seminal method in modern structural biology to obtain insights into proteins' structure, dynamics and function at dilute condition as well as in a cell-like environment or even intracellularly. Usually, 1H, 15N or 13C nuclei are predominantly used for the characterization of the protein of interest. These measurements are limited due to the wealth of chemical shifts and background signals arising from all molecules present in the NMR test tube. On top of that, the protein under study has to be isotopically enriched in nitrogen and/or carbon nuclei enabling to overcome the inherently low natural abundance of 13C and 15N NMR active isotopes. In this way switching to 19F NMR spectroscopy strongly reduces the total amount of signals seen in an NMR spectrum as it turns off background signals and is for this reason extremely attractive for highly-resolved investigations of proteins performance measured directly in cells or in a cell-like environment. Here we show the effective expression and purification of cold shock protein B from Bacillus subtilis (BsCspB) using fluorine labelled phenylalanine or fluorine labelled tryptophan residues. We reveal that fluorine labelled BsCspB represents the same fold on a secondary as tertiary level as seen for the wild type protein independent of the labelling position illuminating the soft character of fluorine insertion. This experimental setup of targeted fluorine labelling sets a profound ground for a broad range of highly-resolved 19F NMR applications to be performed in a complex cellular environment.

Thermal mineralization behavior of PFOA, PFHxA, and PFOS during reactivation of granular activated carbon (GAC) in nitrogen atmosphere.

Waste disposal site is one of the important sinks of chemicals. A significant amount of perfluoroalkyl and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexanoic acid (PFHxA) have been brought into it. Because of their aqueous solubility, PFASs are released to landfill effluent waters, from which PFASs are efficiently collected by adsorption technique using granular activated carbon (GAC). The exhausted GAC is reactivated by heating processes. The mineralization of PFASs during the reactivation process was studied. Being thermally treated in N2 atmosphere, the recovery rate of mineralized fluorine and PFC homologues including short-chained perfluorocarboxylic acids was determined. If the reagent form of PFOA, PFHxA, and PFOS were treated at 700 °C, the recovery of mineralized fluorine was less than 30, 46, and 72 %, respectively. The rate increased to 51, 74, and 70 %, if PFASs were adsorbed onto GAC in advance; moreover, addition of excess sodium hydroxide (NaOH) improved the recovery to 74, 91, and 90 %. Residual PFAS homologue was less than 1 % of the original amount. Steamed condition did not affect destruction. The significant role of GAC was to suppress volatile release of PFASs from thermal ambient, whereas NaOH enhanced destruction and retained mineralized fluorine on the GAC surface. Comparing the recovery of mineralized fluorine, the degradability of PFOS was considered to be higher than PFOA and PFHxA. Whole mass balance missing 9~26 % of initial amount suggested formation of some volatile organofluoro compounds beyond analytical coverage.

Biopolymer-induced morphology control of brushite for enhanced defluorination of drinking water.

Due to the relatively lower potential health risks as well as the good affinity for fluoride anion, calcium-based minerals have been widely carried out for the adsorption of fluoride. The improvement of adsorption capacity can be accomplished by regulation of particle size, shape and structure. Thus, here we report the controllable synthesis of petal-like nanosheets of brushite by using chitosan as a regulator. The addition of chitosan polymer in calcium precursor not only could serve ideal nucleation sites but also could play a vital role in confining the calcium phosphate aggregates and thus controlling the size of the brushite flakes. When the concentration of chitosan was 0.01wt%, the as-synthesized brushite showed nanosheet-structured with the dimensions ranged from 100 to 200nm and displayed outstanding fluoride adsorption capacity of 231.5mg/g according to the fitted Langmuir model, which was comparatively higher than that of the previously reported calcium-based adsorbents. Moreover, the pH change and common co-existing anions in solution almost presented less negative effect on the F- adsorption onto petal-like brushite nanosheets. We hope that these petal-like nanosheets based on green nanotechnology can help to achieve the intention of safe drinking water.

Analysis of Small Ions with Capillary Electrophoresis.

Small inorganic ions are easily separated through capillary electrophoresis because they have a high charge-to-mass ratio and suffer little from some of the undesired phenomenon affecting higher molecular weight species like adsorption to the capillary wall, decomposition, and precipitation. This chapter is focused on the analysis of small ions other than metal ions using capillary electrophoresis. Methods are described for the determination of ions of nitrogen, phosphorus, sulfur, fluorine, chlorine, bromine, and iodine.

[Feasibility and Economic Analysis of Denitrification of Photovoltaic Wastewater Containing High Fluorine].

In order to reduce acid and alkali dosing in wastewater treatment process of polycrystalline silicon by using denitrification after fluoride removal. This experiment studied the feasibility of first removing nitrogen using the denitrification process by start-up denitrifying reactor before fluoride removal. The results showed that the F⁻ concentration in the waste water to had a certain influence on the denitrification. When the concentration of F⁻ was controlled to about 750 mg · L⁻¹, the activity of denitrifying bacteria was not significantly influenced; when the concentration of F⁻ continued to increase, the denitrification efficiency of denitrifying sludge gradually reduced. In wastewater treatment of polycrystalline silicon, if the concentration of F⁻ was kept below 800 mg · L⁻¹, the denitrification performance of denitrifying sludge was not obviously affected. After 93 d operation, the total nitrogen in effluent was stabilized below 50 mg · L⁻¹, the total nitrogen removal efficiency reached 90%, and the removal rate reached 5 kg · (m³ · d)⁻¹. The calculation result showed, compared with the conventional denitrification process after fluoride removal, the proposed process could save about 70% of acid and 100% of alkali dosing, greatly reducing the cost of wastewater treatment.

[Feasibility of Sulfur-based Autotrophic Denitrification of Photovoltaic Wastewater Containing High Fluorine].

Effect of different influent F- concentrations on nitrogen removal efficiency of sulfur-based autotrophic denitrification was researched at room temperature(20-25℃) using domesticated biofilm reactor to explore the feasibility of sulfur-based autotrophic denitrification of photovoltaic wastewater containing high fluorine. The results indicated that when the influent F- concentration was in the range of 0-700 mg·L-1, the nitrogen removal efficiency promoted with rising influent F- concentration. The maximum TN removal rate of 1.0 kg·(m3·d)-1 was attained with the influent F- concentration was 700 mg·L-1. When the influent F- concentration increased to 700-900 mg·L-1, the removal rate of TN reached a stable level at 0.81-0.87 kg·(m3·d)-1 after short-term domestication. When the influent F- concentration was above 900 mg·L-1, the removal efficiency of reactor lowered with rising influent F- concentration. The minimum TN removal rate was 0.4-0.5 kg·(m3·d)-1. Photovoltaic wastewater was used as the influent of the reactor. After 50 d operation, the reactor gained steady denitrification efficiency. With the influent NO3--N concentration of 390-420 mg·L-1, F- concentration of 800 mg·L-1, and HRT of 8.8 h, the maximum TN removal rate of 1.1 kg·(m3·d)-1 was attained. The effluent TN concentration was 15-25 mg·L-1, which met the standard of sewage discharge. Costs of treating photovoltaic wastewater by disposing conventional denitrification and sulfur-based autotrophic denitrification were 2.468 Yuan·t-1 and 2.0728 Yuan·t-1, respectively. Compared with conventional denitrification, the sulfur-based autotrophic denitrification could save more costs.

Determination of fluorine contents in plant samples by means of facilitated extraction with enzyme.

In this study, facilitated extraction with enzyme was employed for the first time to extract fluorine (F) from plants. Feasibility of the proposed method for F analysis was assessed by comparing with the alkali fusion-ion selective electrode (ISE) method. In the extraction procedure, 30 mg of a protease and 0.1 g of a plant sample were added in 10 mL of deionized water. In the absence of sonication, the solution was mechanically shaken for 10 s. A variety of parameters (i.e., the amounts of enzymes used, physical treatment conditions applied, extraction time, temperature, and pH) were optimized to enhance the extraction efficiency of the proposed method. The suitability of the proposed method for various plant samples (i.e., grass, perilla, peanut, hot pepper, and eggplant) was also evaluated. The proposed method involves decreased operation time, simplified extraction procedures, and minimal consumption of hazardous reagents and solvents in comparison with other existing methods. Experimental results demonstrated that facilitated extraction with enzyme is appropriate for the rapid determination of F content in plant samples.

Reductive defluorination of perfluorooctanoic acid by hydrated electrons in a sulfite-mediated UV photochemical system.

A method for reductive degradation of perfluorooctanoic acid (PFOA) was established by using a sulfite/UV process. This process led to a PFOA removal of 100% at about 1h and a defluorination ratio of 88.5% at reaction time of 24h under N2 atmosphere, whereas the use of either UV irradiation or SO3(2-) alone induced little defluorination of PFOA under the same conditions. It was confirmed that the reductive defluorination of PFOA was achieved by hydrated electrons being generated from the photo-conversion of SO3(2-) as a mediator. Theoretical reaction kinetic analysis demonstrated that the generation of hydrated electrons was promoted by increasing either SO3(2-) concentration or solution pH, leading to the acceleration of the PFOA defluorination. Accompanying the reduction of PFOA, a small amount of short-chain perfluorocarboxylic acids, less fluorinated carboxylic acids and perfluorinated alkyl sulfonates were generated, all of which were able to be further degraded with further releasing of fluoride ions. Based on the generation, accumulation and distribution of intermediates, hydrated electrons induced defluorination pathway of PFOA was proposed in a sulfite-mediated UV photochemical system.

Recovery of fluorine from bastnasite as synthetic cryolite by-product.

This paper investigates the development of a new environment friendly approach for treatment of bastnasite. A new process was developed to recover fluorine from bastnasite as synthetic cryolite by-product. The conditions affecting the fluorine removal and recovery in the process, including contact time, acidity, Al(3+) concentration, Al/F molar ratio and different kinds of aluminum salts being used, were investigated. The results indicate that high acidity and large Al/F molar ratio were beneficial to fluoride removal, and that the reaction reached equilibrium after 15 min. The effect of the initial Al(3+) concentration at a certain total Al(3+) amount was slight. Aluminum nitrate was more efficient than aluminum sulfate for the removal of fluoride. Optimum operation parameters for synthesizing cryolite have been obtained and proposed for industrial applications.

A novel liquid plasma AOP device integrating microwaves and ultrasounds and its evaluation in defluorinating perfluorooctanoic acid in aqueous media.

A simplified and energy-saving integrated device consisting of a microwave applicator and an ultrasonic homogenizer has been fabricated to generate liquid plasma in a medium possessing high dielectric factors, for example water. The microwave waveguide and the ultrasonic transducer were interconnected through a tungsten/titanium alloy stick acting both as the microwave antenna and as the horn of the ultrasonic homogenizer. Both microwaves and ultrasonic waves are simultaneously transmitted to the aqueous media through the tungsten tip of the antenna. The microwave discharge liquid plasma was easily generated in solution during ultrasonic cavitation. The simple device was evaluated by carrying out the degradation of the perfluorooctanoic acid (PFOA), a system highly recalcitrant to degradation by conventional advanced oxidation processes (AOPs). PFOA is 59% degraded in an aqueous medium after only 90 s of irradiation by the plasma. Intermediates were identified by electrospray mass spectral techniques in the negative ion mode.

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.

Aluminum nitrate (Al(NO3)3) as defluoridating agent in drinking water soil pots (vessels of earthenware).

Presence of fluoride in drinking water above (and sometimes even below) permissible limit (1.5 ppm according to WHO) leads to fluorosis. Aluminum salts are commonly used as coagulants in water treatments. Aluminum fluoride is less toxic than other fluorides. The concentration of fluoride was determined by the fluoride ion selective electrode method. In this study, Al (NO3)3 was incorporated in different amounts in soil and prepared soil pots by the mixture. It is observed that these soil pots remarkably decrease the concentration of fluoride in drinking water. Langmuir and Freundlich isotherm studies were also carried out.

[Anolyte enhanced electrokinetic remediation of fluorine-contaminated soils].

An experimental study was carried out in order to determine the characteristics of migration and its influencing factor of soil fluorine in the electrokinetic process under different applied voltage and concentration of anolyte. The feasibility of anolyte enhanced on electrokinetic remediation of fluorine-contaminated soil was analyzed. The results show that when deionized water is used as anolyte with the 1.0 V/cm voltage gradient, the cumulative mass of fluorine in catholyte and anolyte are 8.2 mg and 47.7 mg respectively and the removal rate of fluorine is only 8.8%. Anolyte enhanced electrokinetic process can promote effectively the migration of fluoride in soil. When 0.02 mol/L NaOH solutionis employed as the anolyte, the removal rates are 25.9%, 31.2% and 47.3% with 1.0, 1.5 and 2.0 V/cm voltage gradient respectively. As the concentration of anolyte increased to 0.1 mol/L, the removal rates are 55.4%, 61.1% and 73.0%. The electromigration is the main transport mechanism and the electroosmotic flow has an effect on the migration of fluorine in soil. The voltage gradient and the concentration of anolyte are the main factors influencing the removal rate of fluorine in soil. Appropriate anolyte enhanced electrokinetic method can be applied to remediate fluorine from contaminated soil.

[A experimental study on the effect of fluorine capture of calcium based coal briquette].

OBJECTIVE: To study on the fluorine capture effect of calcium based coal briquette with fluorine capture additive in coal-burning fluorosis area. METHODS: Add proper proportions of calcium based fluorine capture additive in high fluorine coal for making coal briquette were added, and were added the fluorine in coal cinder in order to reduce its emission. Meanwhile, to determine the composes of coal briquette were added, the percentage of fluorine in coal cinder and the concentration of fluoride, sulfur dioxide and PM10 were determinated, to evaluate the effect of fluorine capture and the level of door air pollution. RESULT: After pilot-scale studying on the effect of fluorine capture in 30 households at coal-burning fluorosis area in Guiding of Guizhou Province. The average fluorine capture rate were 71.8%, and the average concentration of fluoride were 0.0052 mg/m3, which reduces by 27.8% in comparison with control group and were lower than environmental air quality standard (0.007 mg/m3); and the average concentration of SO2 were 0.67 mg/m3, which reduces 52.8% in comparison with control group and slightly higher than those of indoor air quality standard (0.5 mg/m3). CONCLUSION: The application of the coal briquette made by calcium based fluorine capture additive could reduce the pollution caused by high fluorine coal, could improve the quality of indoor air.

Electrokinetic remediation of fluorine-contaminated soil: conditioning of anolyte.

The feasibility of anolyte conditioning on electrokinetic remediation of fluorine-contaminated soil was investigated with a field soil. The initial concentration of fluorine, pH and water content in the soil were 414mg/kg, 8.91 and 15%, respectively. Because the extraction of fluorine generally increased with the soil pH, the pH of the anode compartment was controlled by circulating strong alkaline solution to enhance the extraction of fluorine during electrokinetic remediation. The removal of fluorine increased with the concentration of the alkaline solution and applied current density and fluorine removed up to 75.6% within 14 days. Additionally, anolyte conditioning sharply increased the electro-osmotic flow, which enhanced the removal of fluorine in this study. In many respects, anolyte conditioning in electrokinetic remediation of fluorine-contaminated soil will be a promising technology.

Perfluorinated compounds and total and extractable organic fluorine in human blood samples from China.

An improved extraction (ion pairing) and cleanup (ENVI-carb and solid phase extraction) method was developed for analysis of perfluorinated compounds (PFCs) in human whole blood samples from China. Ten PFCs including PFOS, PFHxS, PFOSA, PFDoDA, PFUnDA, PFDA, PFNA, PFOA, PFHpA, and PFHxA were detected in the blood samples (n=30) from five cities (Jintan, Nanjing, Guiyang, Beijing, and Shenyang). PFOS was found to be the dominant PFC ranging from 0.446-83.1 ng/mL. Total fluorine (TF) and extractable organic fluorine (EOF) also were measured in the blood samples using combustion ion chromatography for fluorine. Analysis of known PFCs and extractable organic fluorine showed that known PFCs could account for >70% of EOF in samples from Beijing, Shenyang, and Guiyang, whereas known PFCs could only account for approximately 30% of EOF in samples from Jintan. Results of the present study indicated the presence of substantial amounts of unidentified organic fluorine in human blood samples from Jintan. Characterization and identification of these unidentified fluorinated compounds will be instructive.

[Contents of different soil fluorine forms in North Anhui and their affecting factors].

By the method of consecutive extraction, this paper studied the contents and vertical distribution of soil fluorine (F) forms in North Anhui, with their relations to the soil physical and chemical properties analyzed. The results showed that the soil total F (T-F) content in North Anhui was ranged from 265.8 mg . kg(-1) to 612.8 mg . kg(-1), with an average of 423.7 mg . kg(-1), and decreased in the sequence of vegetable soil > fluvo-aquic soil > paddy soil > shajiang black soil > yellow brown soil. Among the T-F, residual F (Res-F) was the main form, occupying > 95% of total F, followed by water soluble F (Ws-F), being about 1.5% of the total, and organic-F (Or-F), Fe and Mn oxide-F (Fe/Mn-F) and exchangeable-F (Ex-F) only had very small amount. The Ws-F content in test soils ranged from 1.35 mg . kg(-1) to 17.98 mg . kg(-1), with a mean value of 6.62 mg . kg(-1). Vegetable soil, fluvo-aquic soil and shajiang black soil had a relatively higher content of Ws-F, while yellow brown soil was in adverse. Soil pH and the contents of soil organic matter, total and available phosphorus, and physical clay were the main factors affecting the contents of various F forms. Soil Ws-F was significantly positively correlated with soil pH and soil total and available phosphorus, soil Ex-F was significantly positively correlated with soil clay ( < 0.01 mm and <0.001 mm), soil Fe/Mn-F was significantly positively correlated with soil total phosphorus, and soil Or-F had a significant positive correlation with soil organic matter. Soil Ws-F content also had a close connection to the parent material. The soil developed from shallow lacustrine and marsh sediments usually had the highest Ws-F content, followed by those developed from Huang River alluvial deposit, Q3 loess, Huaihe River alluvial deposit, and light-texture yellow brown soil, with the mean Ws-F content being 9.05, 8.12, 2.97, 2.05 and 1.91 mg . kg(-1), respectively. The contents of soil Or-F and Fe/Mn-F decreased with increasing soil depth, and those of T-F and Ws-F in vegetable soil were higher in upper than in deeper soil layers.

[Sequential extraction experiments applied to study chemical mobility of fluorine in rocks].

Sequential extraction experiments were used to study the chemical mobility of fluorine in rocks. The results show that there are quite big differences in chemical mobility of fluorine in rocks of different types. Fluorine in carbonate rock is very active, in which the proportion of leachable fluorine is generally more than 75%. Fluorine in black rocks of Lower Cambrian is closely related to their different metamorphosed grades, in which fluorine in black carbonaceous slate with higher metamorphosed grade mostly has lower leachability than black shale and black siliceous rock. Generally speaking, the leachable percentage of fluorine is high in phosphorite rocks and low in phyllite. The leachable fluorine in diabase is in direct proportion to its fluorine concentration. There are some differences in chemical mobility of fluorine in stone coal of different ages. Fluorine in stone coal of Silurian has higher leachability than stone coal of Cambrian.