Screening method for extractable organically bound fluorine (EOF) in river water samples by means of high-resolution-continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS)

An optimized method for PFAS analysis using HR-CS-GFMAS via GaF detection

The analysis of per- and polyfluoroalkyl substances (PFAS) via sum parameters like extractable organic fluorine (EOF) in combination with high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is highly promising regarding fluorine sensitivity and selectivity. However, the HR-CS-GFMAS method includes several drying and heating steps which can lead to losses of volatile PFAS before the molecular formation step using e.g., GaF formation. Hence, the method leads to a strong discrimination of PFAS within the EOF depending on their physical/chemical properties and is therefore associated with reduced accuracy. To reduce this discrepancy and to indicate realistic PFAS pollution values, an optimization of the HR-CS-GFMAS method for PFAS analysis is needed. Hence, we determined fluorine response factors of several PFAS with different physical/chemical properties upon application of systematic optimization steps. We could therefore improve the method's sensitivity for PFAS analysis using a modifier drying pre-treatment step followed by a sequential injection of sample solutions. The highest improvement in sensitivity of volatile PFAS was shown upon addition of a Mg modifier during drying pre-treatment. Thereby, during optimization the relative standard deviation of fluorine response factors could be reduced from 55 % (initial method) to 27 % (optimized method) leading to a more accurate determination of organofluorine sum parameters. The method provides an instrumental LOD and LOQ of β(F) 1.71 μg/L and 5.13 μg/L, respectively. Further validation aimed to investigate several matrix effects with respect to water matrices. Here, substance-specific behavior was observed. For example, perfluorooctanoic acid (PFOA) which was used as calibrator, showed signal suppressions upon high chloride concentrations (>50 mg/L). Hence, a thorough separation of Cl from analytes during sample preparation is needed for accurate sum parameter analysis.

A multi-platform approach for the comprehensive analysis of per- and polyfluoroalkyl substances (PFAS) and fluorine mass balance in commercial ski wax products

The unique properties of per- and polyfluoroalkyl substances (PFAS) have led to their extensive use in consumer products, including ski wax. Based on the risks associated with PFAS, and to align with PFAS regulations, the international ski federation (FIS) implemented a ban on products containing "C8 fluorocarbons/perfluorooctanoate (PFOA)" at all FIS events from the 2021/2022 season, leading manufactures to shift their formulations towards short-chain PFAS chemistries. To date, most studies characterising PFAS in ski waxes have measured a suite of individual substances using targeted analytical approaches. However, the fraction of total fluorine (TF) in the wax accounted for by these substances remains unclear. In this study, we sought to address this question by applying a multi-platform, fluorine mass balance approach to a total of 10 commercially available ski wax products. Analysis of TF by combustion ion chromatography (CIC) revealed concentrations of 1040-51700 μg F g-1 for the different fluorinated waxes. In comparison, extractable organic fluorine (EOF) determined in methanol extracts by CIC (and later confirmed by inductively-coupled plasma-mass spectrometry and 19F- nuclear magnetic resonance spectroscopy) ranged from 92 to 3160 μg g-1, accounting for only 3-8.8 % of total fluorine (TF). Further characterisation of extracts by cyclic ion mobility-mass spectrometry (IMS) revealed 15 individual PFAS with perfluoroalkyl carboxylic acid concentrations up to 33 μg F g-1, and 3 products exceeding the regulatory limit for PFOA (0.025 μg g-1) by a factor of up to 100. The sum of all PFAS accounted for only 0.01-1.0 % of EOF, implying a high percentage of unidentified PFAS, thus, pyrolysis gas chromatography-mass spectrometry was used to provide evidence of the nature of the non-extractable fluorine present in the ski wax products.

Determination of Fluorine by Ion-Selective Electrode and High-Resolution Continuum Source Graphite Furnace Molecular Absorption Spectrometry with Respect to Animal Feed Safety

Fluorine, depending on its concentration and chemical form, is essential or toxic to humans and animals. Therefore, it is crucial to be able to determine it reliably. In this study, fluorine was determined in animal feed after extraction with HCl (gastric juice simulation). The standard potentiometric method with a fluoride-selective electrode (ISE) and newly developed high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GFMAS) method was applied. Feed samples turned out to be a challenge for HR-CS GFMAS. Chemical interferences (formation of competing molecules, CaF, GaCl, and GaP, instead of the target GaF molecule) and spectral effects (including a phosphorous molecule spectrum and atomic lines) were identified. An additional difficulty was caused by reagent contamination with F and memory effects. Difficulties were eliminated/reduced. The quality of ISE analysis was multi-directionally verified (including comprehensive proficiency testing). A risk of inaccuracy at low F concentration, where the calibration relationship is nonlinear, was investigated. The results of both methods were consistent, which confirms the accuracy of the methods and informs that the extracted fluorine is in fluoride form. The results of extensive ISE tests conducted in Poland in 2021-2023 have shown that, in most cases, the fluoride content is significantly lower than the threshold values.

Second-order calibration high-resolution continuum source graphite furnace molecular absorption spectrometry-based determination of bromine and fluorine

In this study, we report the simultaneous determination of bromine and fluorine using Second-Order Calibration High-Resolution Continuum Source Graphite Furnace Molecular Absorption Spectrometry (HR CS MAS). The instrumental data acquired correspond to the time versus wavelength matrix per sample that were analyzed using Parallel Factor Analysis (PARAFAC), along with Unfold and N-way Partial Least Squares combined with a post-calibration step known as Residual Bilinearization (U and N PLS/RBL). Despite the significant difference in sensitivity between bromine and fluorine, all approaches provided reasonably accurate results when predicting both analytes in synthetic mixtures within a controlled environment. The relative prediction error (REP) values for bromine were 29.8 % (PARAFAC), 23.6 % (N-PLS/RBL), and 13.1 % (U-PLS/RBL), while for fluorine, the REP values were 3.4 % (PARAFAC), 3.5 % (N-PLS/RBL), and 3.2 % (U-PLS/RBL). When applying this approach to predict unknown samples, a comparison was made between the estimated nominal concentrations of fluorine and bromine obtained using either a reference method or based on labeled values or spiked mass, and those obtained using the proposed method. It was observed that PARAFAC was unable to predict the samples accurately, whereas the REP values for the prediction of bromine and fluorine using N-PLS/RBL and U-PLS/RBL methods were 19.3 %/19.2 % and 13.6 %/13.1 %, respectively.

From watersheds to dinner plates: Evaluating PFAS exposure through fish consumption in Southeast Michigan

Muscle tissue and organ samples of six different fish species were collected from ten locations in Southeast Michigan's Huron and Rouge watersheds. Per- and polyfluoroalkyl substances (PFAS) were analyzed in 36 samples comprising filets, liver, gut, and eggs using targeted analysis and the direct total oxidizable precursor (dTOP) assay on a subset of six samples. The median concentrations of the ∑PFAS in filets from the Huron and Rouge watersheds were 13 and 6.3 ng/g wet weight (w.w.), respectively. Perfluorooctane sulfonate (PFOS) was the most detected and abundant compound in fish organs, with the liver having the largest overall burden of PFAS. The highest percent increase in targeted PFAS after the dTOP assay was observed in the Catfish filet (552%) while the smallest increase was in the Catfish liver (32%) accounting for 1.3 and 8.1 nMole F/g dry weight (d.w.), respectively. The positive matrix factorization (PMF) analysis revealed three distinct PFAS sources, of which the one attributed to PFOS explained 73% of the data. Results from this work have important implications for fish consumption in Michigan waterways. Among the filet samples analyzed, the calculated daily consumption limit of total PFOS was exceeded in approximately 82% and 91% of samples for adults and children over the age of seven years old, respectively.

Non-extractable PFAS in functional textiles - characterization by complementary methods: oxidation, hydrolysis, and fluorine sum parameters

Per- and polyfluoroalkyl substances (PFAS) are widely used for durable water-repellent finishing of different fabrics and textiles such as outdoor clothing, carpets, medical textiles and more. Existing PFAS extraction techniques followed by target analysis are often insufficient for detecting widely used side-chain fluorinated polymers (SFPs) that are barely or non-extractable. SFPs are typically copolymers consisting of a non-fluorinated backbone with perfluoroalkyl side-chains to obtain desired properties. We compared the accessible analytical information and performance of complementary techniques based on oxidation (dTOP and PhotoTOP assays), hydrolysis (THP assay), standard extraction, extractable organic fluorine (EOF), and total fluorine (TF) with five functional textiles and characterized 7 further textiles only by PhotoTOP oxidation. The results show that when applied directly to textile samples, dTOP and PhotoTOP oxidation and also hydrolysis (THP) are able to capture large fractions of TF in the form of perfluoroalkyl side-chains present in the textiles while methods relying on extracts (EOF, target and non-target analysis) yield much lower fractions of TF (e.g., factor ∼25-50 lower). The conversion of large fractions of the measured TF into PFCAs or FTOHs from fluorinated side chains is in contrast to previous studies. Concentrations ranged from Collapse

Key Words Collapse

MESH Headings

• Fluorine
• Hydrolysis
• Textiles/analysis
• Fluorocarbon Polymers/analysis
• Fluorocarbon Polymers/chemistry
• Polymers
• Carboxylic Acids/analysis
• Fluorocarbons/analysis

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Affiliation(s)

Jonathan Zweigle Environmental Analytical Chemistry, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany.
Catharina Capitain Environmental Analytical Chemistry, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany.
Fabian Simon Federal Institute for Materials Research and Testing (BAM), Division 1.1 - Inorganic Trace Analysis, Richard-Willstätter-Straße 11, 12489 Berlin, Germany
Philipp Roesch Federal Institute for Materials Research and Testing (BAM), Division 4.3 - Contaminant Transfer and Environmental Technologies, Unter den Eichen 87, 12205, Berlin, Germany
Boris Bugsel Environmental Analytical Chemistry, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany.
Christian Zwiener Environmental Analytical Chemistry, Department of Geosciences, University of Tübingen, Schnarrenbergstraße 94-96, 72076 Tübingen, Germany.

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Water pollution risks by smoldering fires in degraded peatlands

Climate change may increase the overall susceptibility of peatlands to fire. Smoldering fires in peatlands can cause substantial emissions of greenhouse gases. It is, however, less clear how smoldering affects the soil pore water quality. In this study, soil samples were collected from agricultural fen and disturbed bog study sites in Germany and Lithuania to quantify the effect of peat burning on pore water composition. The samples were air dried and smoldered under ignition temperature (approximately 200 °C) with different durations (0, 2, 5, and 10 h). Pore water samples were extracted from the soil to determine dissolved organic carbon (DOC) concentrations, dissolved organic matter (DOM) fractions, fluoride, extractable organically bound fluorine (EOF), and sulfate concentrations. The results showed that soil smoldering changes the peat pore water chemistry and that changes differ between fens and bogs. The smoldering duration is likewise influential. For fen grasslands, 2 and 5 h of smoldering of peat caused a >10-fold increase in DOC (up to 1600 mg L^-1) and EOF concentrations. The fluoride (up to 60 mg L^-1) and sulfate concentrations substantially exceeded WHO drinking water guidelines. In contrast, the temperature treatment decreased the DOC concentrations of samples from raised bogs by 90 %. The fluoride concentrations decreased, but sulfate concentrations increased after smoldering of the bog samples. DOC, fluoride, and sulfate concentrations of bogs varied significantly between the smoldering duration treatments. For all peat samples, the extracted DOM was dominated by humic-like substances before smoldering, but the fraction of low molecular weight substances increased after smoldering combustion. In conclusion, smoldering alters the biogeochemical processes in both peatland types and possibly impair the water quality of adjacent water resources especially in fen peat landscapes.

Quantification and characterization of PFASs in suspended particulate matter (SPM) of German rivers using EOF, dTOPA, (non-)target HRMS

In this study, we compare analytical methods for PFAS determination-target analysis, non-target screening (NTS), direct total oxidizable precursor assay (dTOPA) and extractable organically bound fluorine (EOF). Therefore, suspended particulate matter (SPM) samples from German rivers at different locations in time series from 2005 to 2020 were analyzed to investigate temporal and spatially resolved trends. In this study 3 PFAS mass balances approaches were utilized: (i) PFAA target vs. PFAS dTOPA, (ii) PFAS target vs. EOF and (iii) PFAS target vs. PFAS dTOPA vs. organofluorines NTS vs. EOF. Mass balance approach (i) revealed high proportions of precursor substances in SPM samples. For the time resolved analysis an increase from 94% (2005) to 97% in 2019 was observable. Also for the spatial resolved analysis precursor proportions were high with >84% at all sampling sites. Mass balance approach (ii) showed that the unidentified EOF (uEOF) fraction increased over time from 82% (2005) to 99% (2019). Furthermore, along the river courses the uEOF increased. In the combined mass balance approach (iii) using 4 different analytical approaches EOF fractions were further unraveled. The EOF pattern was fully explainable at the sampling sites at Saar and Elbe rivers. For the time resolved analysis, an increased proportion of the EOF was now explainable. However, still 27% of the EOF for the time resolved analysis and 25% of the EOF for the spatial resolved analysis remained unknown. Therefore, in a complementary approach, both the EOF and dTOPA reveal unknown gaps in the PFAS mass balance and are valuable contributions to PFAS risk assessment. Further research is needed to identify organofluorines summarized in the EOF parameter.

Substances of emerging concern in Baltic Sea water: Review on methodological advances for the environmental assessment and proposal for future monitoring

The Baltic Sea is among the most polluted seas worldwide. Anthropogenic contaminants are mainly introduced via riverine discharge and atmospheric deposition. Regional and international measures have successfully been employed to reduce concentrations of several legacy contaminants. However, current Baltic Sea monitoring programs do not address compounds of emerging concern. Hence, potentially harmful pharmaceuticals, UV filters, polar pesticides, estrogenic compounds, per- and polyfluoroalkyl substances, or naturally produced algal toxins are not taken into account during the assessment of the state of the Baltic Sea. Herein, we conducted literature searches based on systematic approaches and compiled reported data on these substances in Baltic Sea surface water and on methodological advances for sample processing and chemical as well as effect-based analysis of these analytically challenging marine pollutants. Finally, we provide recommendations for improvement of future contaminant and risk assessment in the Baltic Sea, which revolve around a combination of both chemical and effect-based analyses.

A fast and simple PFAS extraction method utilizing HR-CS-GFMAS for soil samples

Here, we describe an optimized fast and simple extraction method for the determination of per- and polyfluorinated alkyl substances (PFASs) in soils utilizing high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). To omit the bias of the solid phase extraction (SPE) step commonly used during the analysis of extractable organically bound fluorine (EOF) we optimized a fast and simple SPE-free extraction method. The developed extraction method consists of a liquid-solid extraction using acidified methanol without any additional SPE. Four extraction steps were representative to determine a high proportion of the EOF (>80% of eight extractions). Comparison of the optimized method with and without an additional SPE clean-up step revealed a drastic underestimation of EOF concentrations using SPE. Differences of up to 94% were observed which were not explainable by coextracted inorganic fluoride. Therefore, not only a more accurate but also a more economic as well as ecologic method (bypassing of unnecessary SPE) was developed. The procedural limit of quantification (LOQ) of the developed method was 10.30 μg/kg which was sufficient for quantifying EOF concentrations in all tested samples. For future PFAS monitoring and potential regulative decisions the herein presented optimized extraction method can offer a valuable contribution.

Fluorine mass balance analysis of selected environmental samples from Norway

The presence of unidentified organofluorine compounds (UOF) has been investigated in recent publication, but their environmental occurrence is still poorly understood. Fluorine mass balance analysis was performed on environmental samples from lake Mjøsa and river Alna (surface water (n = 9), sediment (n = 5) and fish liver (n = 4)) and sewage samples from Oslo (n = 5), to reveal to the fraction of UOF. In samples that had extractable organofluorine (EOF) concentrations above the limit of detection (LoD), more than 70% of their EOF could not be accounted for by the 37 PFAS monitored in this study. The surface water samples from lake Mjøsa had EOF concentrations several times higher than what has been reported elsewhere in Nordic nations. The flux of EOF in river Alna and selected sewage pipes revealed that it was 1-2 orders of magnitude higher than the flux of the measured PFAS. The elevated concentrations of EOF in all samples pose a potential health and environmental hazard, as their composition remains mostly unknown.

Method development for determination of organic fluorine in gasoline and its components using high-resolution continuum source flame molecular absorption spectrometry with gallium fluoride as a target molecule

High-resolution continuum source molecular absorption spectrometry (HR-CS MAS) has been developing fast for fluorine determination, but neither flame nor graphite furnace technique have ever been applied for the analysis of petroleum or its products. Hydrogen fluoride can be applied in technologies of gasoline components production, unfortunately, arising organic fluorides can contaminate final product. The aim of this work was development of fast and simple HR-CS MAS method, with an ordinary air-acetylene flame, for determination of organic F in gasoline and its components. Gallium fluoride as a target molecule was the imposing choice, because Ga undergoes atomization at relatively low temperature, and the GaF molecule is known to provide good sensitivity in F determination. Severe difficulties have arisen to get higher concentration of gallium (as Ga(III)acetylacetonate) in the measured (xylene) solution. Furthermore, depending on the flame character, the spectrum of the GaF molecule at the most sensitive 211.248 nm rotational "line"could have been disturbed by intensive noise (a case of too rich flame) or overlapped by the OH molecule spectrum (a case of too lean flame). The effects, as well as sensitivity of F determination, depended on the sample volatility and its dilution ratio. The difficulties have been overcome by adjusting the solution aspiration rate and the additional air flow rate to get not-disturbed baseline. The least square background correction (LSBC) with the OH molecule spectrum as the correction spectrum (the OH molecule spectrum intentionally generated for the first time) and the standard addition calibration have been also applied. Huge difference in sensitivity, up to one order of magnitude, depending on the F compound volatility and its chemical character was stated. A standard giving the best sensitivity (heptafluorobutanol) turned out to be the most suitable for calibration in analysis of real samples (satisfactory agreement with results of combustion ion chromatography). It was found that HF introduced into the solution of the investigated sample does not contribute to the increase of F signal. Using 5000 mg L^-1 of Ga in a solution, the best characteristic concentration and detection limit are 3.2 mg L^-1 and 0.93 mg L^-1, respectively. The developed method enabled to identify high contamination of some gasoline components with organic F species, which constituted significant corrosion and environmental threat.

Determination of organically bound fluorine sum parameters in river water samples-comparison of combustion ion chromatography (CIC) and high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS)

In this study, we compare combustion ion chromatography (CIC) and high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) with respect to their applicability for determining organically bound fluorine sum parameters. Extractable (EOF) and adsorbable (AOF) organically bound fluorine as well as total fluorine (TF) were measured in samples from river Spree in Berlin, Germany, to reveal the advantages and disadvantages of the two techniques used as well as the two established fluorine sum parameters AOF and EOF. TF concentrations determined via HR-CS-GFMAS and CIC were comparable between 148 and 270 μg/L. On average, AOF concentrations were higher than EOF concentrations, with AOF making up 0.14–0.81% of TF (determined using CIC) and EOF 0.04–0.28% of TF (determined using HR-CS-GFMAS). The results obtained by the two independent methods were in good agreement. It turned out that HR-CS-GFMAS is a more sensitive and precise method for fluorine analysis compared to CIC. EOF and AOF are comparable tools in risk evaluation for the emerging pollutants per- and polyfluorinated alkyl substances; however, EOF is much faster to conduct.