Perfluorooctanoate Sulfonate Research Articles

Role of LiOH in Aqueous Electrocatalytic Defluorination of Perfluorooctanoic Sulfonate: Efficient Li-F Ion Pairing Prevents Anode Fouling by Produced Fluoride.

Per- and polyfluoroalkyl substances (PFAS) pose a significant environmental and health threat due to their high toxicity, widespread use, and persistence in the environment. Electrochemical methods have emerged as promising approaches for PFAS destruction, offering cost-effective and energy-efficient solutions. We established recently that electrocatalysis with nonprecious materials enabled the complete defluorination of perfluorooctanesulfonate (PFOS) in aqueous 8.0 M LiOH. Here, we reveal the mechanistic role of LiOH in the efficient aqueous electrocatalytic PFOS defluorination. Our results demonstrate that synergistic effects of high lithium and high hydroxide ion concentrations are essential for complete PFOS defluorination. Two-dimensional NMR data of electrolytes post pulsed electrolysis provide experimental evidence for Li-F ion pairing, which plays a crucial role in preventing anode fouling by produced fluoride, thus enabling sustained C-F bond cleavage. This Li-F ion pairing was increased at high pH, and elevated temperatures enhanced diffusion of Li-F ion pairs into the bulk electrolyte. High hydroxide ion concentrations additionally removed fluoride from the anode surface by competitive adsorption, corroborated by XPS data. Our findings provide quantitative mechanistic insights into the electrocatalytic defluorination process and offer a general route of enhancing the efficiency of anodic PFAS defluorination.

Perfluoroalkyl functionalized-Au nanoparticle sensor: Employing rate of spectrum shifting for highly selective and sensitive detection of per- and polyfluoroalkyl substances (PFASs) in aqueous environments

Per- and polyfluoroalkyl substances (PFASs) are emerging contaminants detected ubiquitously and have negative impacts on human health and ecosystem; thus, developing in-situ sensing technique is important to ensure safety. Herein, we report a novel colorimetric-based sensor with perfluoroalkyl receptor attached to citrate coated gold nanoparticles (Citrate-Au NPs) that can detect several PFASs including perfluorocarboxylates with different chain lengths (PFHxA, PFOA, PFNA, PFDA), perfluorooctanoic sulfonate (PFOS), and perfluorooctanoic phosphonate (PFOPA). The sensor detects PFASs utilizing fluorous interaction between PFASs and the perfluoroalkyl receptor of Citrate-Au NPs in a solution at a fixed salt concentration, inducing changes in nanoparticle dispersity and the solution color. The rate of spectrum shift was linearly dependent on PFASs concentrations. Citrate-Au NPs with size between 29 – 109 nm were synthesized by adjusting citrate/Au molar ratios, and 78 nm showed the best sensitivity to PFOA concentration (with level of detection of 4.96 µM). Citrate-Au NPs only interacted with PFASs with perfluoroalkyl length > 4 and not with non-fluorinated alkyl compound (nonanoic acid). The performance of Citrate-Au NP based sensor was strongly dependent on the chain length of the perfluoroalkyl group and the head functional group; higher sensitivity was observed with longer chain over shorter chain, and with sulfonate functional group over carboxylate and phosphonate. The sensor was tested using real water samples (i.e., tap water, filtered river water), and it was found that the sensor is capable of detecting PFASs in these conditions if calibrated with the corresponding water matrix. While further optimization is needed, this study demonstrated new capability of Citrate-Au NPs based sensor for detection of PFASs in water.

Occurrence of Major Perfluorinated Alkylate Substances in Human Blood and Target Organs.

Human exposure to perfluorinated alkylate substances (PFASs) is usually assessed from the concentrations in serum or plasma, assuming one-compartment toxicokinetics. To characterize body distributions of major PFASs, we obtained and extracted tissue samples from 19 forensic autopsies of healthy adult subjects who had died suddenly and were not known to have elevated levels of PFAS exposure. As target organs of toxicological importance, we selected the liver, kidneys, lungs, spleen, and brain, as well as whole blood. Samples weighing about 0.1 g were analyzed by liquid chromatography coupled to triple mass spectrometers. Minor variations in PFAS concentrations were found between the kidney cortex and medulla and between lung lobes. Organ concentrations of perfluorooctanoic sulfonate (PFOS) and perfluorononanoate (PFNA) correlated well with blood concentrations, while perfluorooctanoate (PFOA) and perfluorohexanoic sulfonate (PFHxS) showed more variable associations. Likewise, the liver concentrations correlated well with those of other organs. Calculations of relative distributions were carried out to assess the interdependence of organ retentions. Equilibrium model predictions largely explained the observed PFAS distributions, except for the brain. Although the samples were small and affected by a possible lack of homogeneity, these findings support the use of blood-PFAS concentrations as a measure of PFAS exposure, with the liver possibly acting as the main organ of retention.

Ultra-low current electrospray ionization of chloroform solution for the analysis of perfluorinated sulfonic acids.

Femtoamp and picoamp electrospray ionization (ESI) characteristics of a nonpolar solvent were explored. The direct ESI mass spectrometry analysis of chloroform extract solution enabled rapid analysis of perfluorinated sulfonic acid analytes in drinking water. Neat chloroform solvent and extracts were directly used in a typical wire-in ESI setup using micrometer emitter tips. Ionization currents were measured with femtoamp sensitivity while ramping the spray voltage from 0 to -5000 V. Methanol was used as a comparison to illustrate thecharacteristics of electrospraying chloroform. The effects of spray voltage and inlet temperature were studied. A liquid-liquid extraction workflow was developed to analyze perfluorooctanoate sulfonate (PFOS) in drinking water using an ion-trap mass spectrometer. The ionization onset of chloroform solution was 41 ± 17 fA at 300 V. The ionization current gradually increased with voltage while remaining below 100 pA when using voltages up to -5000 V. The ion signal of PFOS was significantly enhanced to improve the limit of detection (LoD) to 25 ppt in chloroform. Coupled with a liquid-liquid extraction workflow, LoD of 0.38-5.1ppt and a quantitation range of 5-400 ppt were achieved for perfluorinated sulfonic compounds in 1-ml water samples. Femtoamp and picoamp modes expand the solvent compatibility range of ESI and can enable quantitative analysis in parts per trillion (ppt) concentrations.

Multi-head cationic siloxane based “turn on” fluorescent system for selective detection of perfluorooctanoic sulfonate (PFOS)

Perfluorooctane sulfonate (PFOS) has attracted more and more attention because of its persistence, bioaccumulation and potential ecotoxicity. Although the electrostatic interaction between surfactant and dye has been used for PFOS detection, there still exist a problem in selectivity and some phenomenon also should be explored. Herein, two types of multi-head cationic siloxanes (M1 and D1) based “turn on” fluorescent system were designed for PFOS detection and were further used for exploring interaction between surfactant and dye. Cationic group (quaternary ammonium salt) was introduced into siloxane via thiol-ene click reaction. Two types of multi-head siloxanes with different amounts of cationic group and steric structure were obtained and showed a high selective detection for PFOS. More important, we further explored the possible response mechanism by contracting fluorescence behavior of three types of cationic molecules (single-head, two-head, and four-head cationic group) and speculated the high selectivity was derived from the synergistic effect between electrostatic interaction and steric hindrance. Furthermore, the exploration about surfactant-dye interaction in this work provide a deeper understanding for electrostatic action and its application.

Cheap and Simple Electrochemical Sensors with Closed-Cell MIP-Coated Bipolar Electrode Arrays for Sub-Ppb Detection of PFOS in Water

Growing public awareness of the health risks associated with long-term exposure to poly- and perfluoroalkyl substances (PFAS) has necessitated the development of low-cost, point of use, and accessible methods for detection in water. Efforts to develop such methods have been stymied by their very low concentrations (part per trillion level) and remarkable chemical stability. Recently, our group has developed a new technique termed optical anodic stripping voltammetry (o-ASV) which couples a closed-cell continuous bipolar electrochemical (BPE) sensor with cathodic electrochemiluminescence (ECL) reporting for the simple, rapid, and point-of-use detection of heavy metal ions in water. The work presented here, on the other hand, is aimed at adapting this same sensor transduction scheme to the quantitation of PFAS compounds. The primary challenge is accommodating the electrochemical inactivity exhibited by most PFAS compounds. This presentation will describe development of a molecular imprint polymer (MIP) layer on the surface of the sensor BPE to promote both selectivity and sensitivity in detection. The MIP layer works in combination with a proxy redox probe, ferrocene carboxylate (FcCOOH), to transduce the current signal to an optical readout that can be read with a digital camera like those on most modern cellular phones. This presentation will focus on describing the nature of the sensor transduction principle as applied to non-redox active PFAS compounds like perfluorooctanoic sulfonate (PFOS). A specific discussion of the operative mechanistic components of detection will be addressed, including the interplay between molecular adsorption, diffusion, and electrochemical transformation. Details of the stability and functional longevity of the electropolymerized MIP layer will be discussed along with its application to other isomorphic PFAS compounds. Finally, a new simple device fabrication procedure will be highlighted as it pertains to the open-source production of these novel sensors.

Regeneration of per- and polyfluoroalkyl substance-laden granular activated carbon using a solvent based technology

Per- and polyfluoroalkyl substances (PFAS) are a large class of chemicals widely used for many commercial and industrial applications and have resulted in contamination at sites across globally. Pump-and-treat systems, groundwater extraction, and ex situ treatment using granular activated carbon (GAC) are being implemented, either in full or pilot scale, to treat PFAS-impacted groundwater and drinking water. The only current method of regenerating spent GAC is to reactivate it at temperatures greater than 1000 °C, which requires large amounts of energy and is quite expensive. This research focused on development and demonstration of an effective GAC regeneration technology using a solvent-based method for PFAS-laden GAC used in water treatment. Two different organic solvents (ethanol and isopropyl alcohol) with 0.5% and 1.0% ammonium hydroxide (NH4OH) as a base additive were tested to determine the most effective regenerant solution to remove PFAS from the contaminated GAC. Based on column tests using laboratory-contaminated GAC with perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS), the solvent-base mix (SBM) of ethanol with 0.5% NH4OH was found to be the optimum performing regenerant solution. The GAC life span assessment showed that solvent-regenerated GAC performed similar to virgin GAC without losing its optimal performance of PFAS sorption. Further, the solvent-regenerated GAC showed optimal performance even after four cycles of solvent regenerations tested using the optimum SBM. Average percent removal in laboratory-contaminated GAC using the optimum SBM was 65% and 93% for PFOS and PFOA, respectively. Four field-spent GAC samples were also regenerated using the optimum SBM. Percent removal from these samples was found to be in range of 55%–68%. The type of GAC used, level of contamination and type of PFAS present, water type and quality, and the presence of co-contaminants may have influenced the removal capacity. Distillation experiments have shown that it is feasible to concentrate the spent solvent prior to disposal, which reduces the amount of PFAS-contaminated solvent waste produced in regeneration cycles.

Associations between the serum levels of PFOS/PFOA and IgG N-glycosylation in adult or children

BackgroundPerfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS) have been shown to be associated with disease development. Immunoglobulin G (IgG) N-glycosylation plays a vital role in human immune system and inflammatory activities. Altered IgG glycosylation was one of the molecular markers of various disorders. However, whether the chemicals affect IgG glycosylation has not been investigated. MethodsSerum samples of 190 individuals including 95 adults and 95 children were selected based on the sex, age and PFOA/PFOS concentration. IgG N-glycome profile was obtained from glycan release, derivatization, and MALDI-MS analysis. One-factor ANOVA test was performed to analyze the association between different levels of PFOS/PFOA and IgG glycosylation changes. Evaluation of the diagnostic performance of significantly changed IgG glycosylation was performed by receiver operating characteristic curve. PFOS/PFOA concentrations were studied in relation to IgG glycosylation by 3D-nonlinear regression analysis. Results10 of the 28 individual IgG glycans were significantly altered between different levels of PFOS/PFOA in adult serum. Among children with high serum levels of PFOS or PFOA, a total of 12 IgG N-glycans were markedly different from those with lower serum PFOS/PFOA. The glycan derived traits for adults with higher serum PFOS or PFOA were marked by significant alterations in IgG digalactosylation, agalactosylation, fucosylation, fucosylated sialylation, and disialylation. Similarly, pronounced changes in agalactosylation, digalactosylation, mono-sialylation and total sialylation, as well as neutral and sialo bisection, were associated with elevated serum PFOS or PFOA in children. Several glycans gained moderately accurate scores of area under the curve for diagnosis of PFOS or PFOA pollution. Nonlinear surface fitting showed the independent or coordinate effect of PFOS or PFOA on the expression of IgG glycosylation. ConclusionsHigh levels of PFOS or PFOA in human serum were strongly associated with altered IgG glycosylation and therefore are a potential risk factor for the development of diseases.

Synergistic Effect of Metal-Organic Framework/Gallic Acid in Enhanced Laser Desorption/Ionization Mass Spectrometry.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has become an indispensable tool for high-throughput analysis of macromolecules, but many challenges still remain in detection of small molecules due to the severe matrix-related background interference in the low-molecular-weight ranges (MW < 700 Da). Herein, a gallic acid (GA)-functionalized zirconium 1,4-dicarboxybenzene metal-organic framework (MOF) (denoted as UiO-66-GA) was designed to serve as a new substrate, and a novel strategy on the basis of the synergistic effect of MOF and GA was developed to enhance the LDI process. In comparison with conventional organic matrices, the UiO-66-GA substrate showed superior LDI performance in the analysis of a wide variety of molecules including amino acids, unsaturated fatty acids, bisphenols (BPs), oligosaccharides, peptides, protein, and polyethylene glycol (PEG) of various average molecular weights from 200 to 10000. Perfluorooctanoic sulfonate (PFOS) was used to evaluate the ability of quantitative analysis, and its corresponding limit of detection as low as 1 fmol was achieved. High sensitivity and good salt tolerance of the UiO-66-GA-assisted LDI-MS were allowed to determine ultratrace PFOS in the spiked human urine and serum samples. In addition, the synergistic mechanism of MOF and GA in the enhanced LDI process was investigated by comprehensively comparing GA- and its analogue-functionalized UiO-66, and the results revealed that two aspects contributed to the enhanced LDI process: (1) an enhancement in the metal-phenolic coordination system of UiO-66-GA promoted laser absorption and energy transfer; (2) introduction of carboxyl and hydroxyl groups of GA onto UiO-66 facilitated the LDI process in both positive and negative ion modes. This work expands a new domain for the MOF applications and provides a promising alternative for various molecule analyses.

One-step hydrothermal synthesis of down/up-conversion luminescence F-doped carbon quantum dots for label-free detection of Fe3+

In this work, a kind of down/up-conversion luminescent F-doped carbon dots (F-CDs) with high fluorescence quantum yield was prepared by one-step hydrothermal treatment of perfluorooctanoic sulfonate (PFOS) and was used for the label-free detection of Fe3+. The obtained F-CDs have a uniform and monodispersed size at 4 nm, and show good properties such as down/up-conversion luminescence, good water-solubility, anti-photobleaching, salt tolerance, and high fluorescence quantum yield of about 35.2%. The down/up-conversion photoluminescence emissions both are independent on the excitation and both the emission peaks are at 447 nm, which indicates it is promising to be used as fluorescent whitening agent. Based on the quenching effect of iron ions, a simple, sensitive, low-cost and label-free fluorescent assay for iron ions has been developed with a liner range of 1–100 μM and a limit of detection (LOD) of 10 nM. Furthermore, the label-free nanoprobe has been successfully applied for the detection of Fe3+ in real samples.

Elucidating the fate of perfluorooctanoate sulfonate using a rainbow trout (Oncorhynchus mykiss) physiologically-based toxicokinetic model.

Per- and poly-fluorinated substances (PFAS) are widely found in freshwater ecosystems because of their resistance to degradation. Among them, several long-chain perfluoroalkyl acids bioaccumulate in aquatic vertebrates, but our understanding of the mechanisms of absorption, distribution and elimination is still limited in fish. For this purpose, we developed a 10-compartment physiologically-based toxicokinetic (PBTK) model to elucidate perfluorooctane sulfonate (PFOS) kinetics in adult rainbow trout. This PBTK model included various physiological characteristics: blood perfusion to each organ, plasmatic fraction, PFOS free fraction, and growth of individuals. The parameters were optimized using Bayesian inferences. First, only PFOS absorption by diet was considered in the model as well as its elimination by urine, bile and feces. Then two mechanistic hypotheses, assumed to govern PFOS toxicokinetics in fish, namely the enterohepatic cycle and the absorption and elimination though gills, were tested. Improvement of the model's fit to the data was studied in each organ by comparing predictions with observed data using relative error. The experimental data set was obtained from an exposure experiment, where adult rainbow trout were fed with a PFOS-spiked diet for 42 days, followed by a 35-day depuration period. In all cases, PFOS concentrations were accurately predicted in organs and feces by the model. The results of this PBTK model demonstrated that feces represented the major elimination route for PFOS while urine was a minor route. Also, PFOS branchial uptake can be substantial despite low concentrations of the compound in water, and elimination through gills should not be neglected. Finally, the enterohepatic cycle is likely to play a minor role in PFOS toxicokinetics. Overall, this PBTK model accurately described PFOS distribution in rainbow trout and provides information on the relative contribution of absorption and elimination pathways.

Influence of groundwater conditions and co‐contaminants on sorption of perfluoroalkyl compounds on granular activated carbon

AbstractPer and polyfluoroalkyl substances (PFAS) are emerging and persistent organic pollutants that have been detected in many environmental media, humans, and wildlife. A common method to effectively remove PFAS from water is adsorption by activated carbon. Preliminary sorption experiments were conducted using five characterized Calgon Corporation coal‐based granular activated carbon (GAC; F100, F200, F816, F300, and F400), one coconut‐based GAC (CBC‐OLC 12 × 30), and one Jacobi Corporation coal‐based GAC (Omni‐G 12 × 40). Sorption of four representative PFAS onto each GAC was measured to select the most favorable carbon sources. F400 and CBC were chosen based on their performance in preliminary PFAS sorption experiments and contrasting properties. Freundlich and Langmuir isotherm models were developed for perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS) at an initial concentration of 1 mg/L. Sorption capacities were determined for PFOA and PFOS individually and in the mixture. Individual compounds showed higher sorption than when present in the mixture for both PFOA and PFOS. PFOS showed higher sorption than PFOA both individually and in the mixture and F400 showed higher sorption capacity than CBC. The presence of co‐contaminants (kerosene, trichloroethylene, and ethanol), and variations in groundwater conditions (pH, presence of anions, naturally occurring organic matter, and iron oxides) demonstrated limited impact on the sorption of PFAS onto GAC under the experimental conditions tested.

Neuroprotective effects of blueberry anthocyanins against perfluorooctanoic sulfonate on planarian Dugesia japonica

In this study, the planarian Dugesia japonica was exposed to perfluorooctane sulfonate (PFOS) and blueberry anthocyanins (ANT) for 1–10 days to investigate the protective effects of ANT on neurotoxicity and DNA damage induced by PFOS. The expression of neural related genes (Djnlg, DjFoxD, DjFoxG, DjotxA, and DjotxB) in D. japonica following exposure was determined using quantitative real-time PCR (qPCR). Immunofluorescence was performed to determine the alterations in neural morphology. In addition, ELISA kits were used to measure level of the neurotransmitters Dopamine (DA), serotonin (5-HT) and γ-aminobutyric acid (GABA). Furthermore, single cell gel electrophoresis was measured to analyze DNA damage. In this study, PFOS treatment induced neural morphology defects, alterations in neural-related gene expression, alterations in neurotransmitter levels, and DNA damage. However, co-exposure to ANT and PFOS mitigated the damage to D. japonica induced by PFOS. Restoration of neurotransmitter contents and neural related genes expression were observed in planarians following co-application of ANT and PFOS, immunofluorescence showed that nerve morphology almost recovered, and DNA damage was decreased. The results of this study showed that ANT may have a protective effect against PFOS induced neurotoxicity and DNA damage.

Concentrations and trends of perfluorinated chemicals in potential indoor sources from 2007 through 2011 in the US

Certain perfluorinated chemicals (PFCs) in consumer products used indoors are potential indoor PFCs sources and have been associated with developmental toxicity and other adverse health effects in laboratory animals (Lao et al., 2007). The concentrations of selected PFCs including perfluorooctanoic acid (PFOA) and other perfluorocarboxylic acids (PFCAs), in 35 selected consumer products that are commonly used in indoors were measured from the year of 2007 through 2011. The products collected included carpet, commercial carpet-care liquids, household carpet/fabric-care liquids, treated apparel, treated home textiles, treated non-woven medical garments, floor waxes, food-contact paper, membranes for apparel, and thread-sealant tapes. They were purchased from retail outlets in the United States between March 2007 and September 2011. The perfluorocarboxylic acid (PFCA) contents in the products have shown an overall downward trend. However, PFOA (C8) could still be detected in many products that we analyzed. Reductions of PFCAs were shown in both short-chain PFCAs (sum of C4 to C7) and long-chain PFCAs (sum of C8 to C12) over the study period. There were no significant changes observed between short-chain PFCAs and long-chain PFCAs. Fourteen products were analyzed to determine the amounts of perfluoroalkyl sulfonates (PFASs) they contained. These limited data show the pronounced increase of perfluoro-butane sulfonate (PFBS), an alternative to perfluorooctanoic sulfonate (PFOS), in the samples. A longer and wider range of study will be required to confirm this observed trend.

Trace level determination of perfluorinated compounds in water by direct injection

A new, fast LC–MS/MS method for the determination of perfluorinated surfactants in water samples by direct injection without pre-concentration is reported. The current method requires only 4 min to analyze nine perfluoroalkyl compounds in a single analytical run. Standard addition and internal standard quantification were used to determine the level of some perfluorinated carboxylic and sulfonic acids, including perfluorooctanoic sulfonate (PFOS) and perfluorooctanoic acid (PFOA), in Great Lakes water samples. Statistically significant differences were observed between the results obtained using different quantification methods. A relatively small difference between the PFOS values obtained with the standard addition method, with and without peak area normalization, clearly indicates that standard addition is the best quantification method when mass-labeled standards are not available. Based on the paired t-test statistical analysis, the concentrations calculated using external standardization were the least accurate, with the highest mean difference from the standard addition calculated values. Both PFOS and PFOA were present at less than 10 ng l −1 in all Great Lake samples. Higher levels were detected in tributaries of Lake Ontario and effluents from sewage treatment plants.