Gas chromatography–tandem mass spectrometry with atmospheric pressure chemical ionization for fluorotelomer alcohols and perfluorinated sulfonamides determination

Target and non-target analyses of neutral per- and polyfluoroalkyl substances from fluorochemical industries using GC-MS/MS and GC-TOF: Insights on their environmental fate

Novel and emerging per- and polyfluoroalkyl substances (PFAS) are a key issue of concern in global environmental studies. In this study, air, sediment, and wastewater samples were collected from areas in and/or surrounded by fluorochemical-related industrial facilities to characterize the contamination profiles of neutral and novel PFAS (n-PFAS) using a gas chromatograph-based target and non-target analyses. Fluorotelomer alcohols were predominant in the samples, accounting for 80 % of the n-PFAS, followed by fluorotelomer acrylates. Air samples collected proximate to the durable water repellent (DWR) facility had the highest concentration of n-PFAS, which was approximately two orders of magnitude higher than those found in others. Non-target analysis identified fluorotelomer iodides and fluorotelomer methacrylate in multiple matrices near DWR facilities, indicating significant contamination of n-PFAS. Levels of both C6- and C8-based PFAS reflected a shift in usage patterns from C8- to C6-based fluorochemicals. Matrix-dependent profiles of n-PFAS revealed that shorter-chain (e.g., C6) and longer-chain (>C8) PFAS were predominant in air and sediment, respectively, implying that air and sediment are mobile and secondary sources of PFAS. Untreated and treated industrial wastewater also contained n-PFAS and their transformation products. The findings shed light on our understanding of the multi-matrix distribution and transport of PFAS.

Molecular detection of per- and polyfluoroalkyl substances in water using time-of-flight secondary ion mass spectrometry

Detection of per- and polyfluoroalkyl substances (PFASs) is crucial in environmental mitigation and remediation of these persistent pollutants. We demonstrate that time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a viable technique to analyze and identify these substances at parts per trillion (ppt) level in real field samples without complicated sample preparation due to its superior surface sensitivity. Several representative PFAS compounds, such as perfluorooctanesulfonic acid (PFOS), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluoheptanoic acid (PFHpA), and perfluorononanoic acid (PFNA), and real-world groundwater samples collected from monitoring wells installed around at a municipal wastewater treatment plant located in Southern California were analyzed in this work. ToF-SIMS spectral comparison depicts sensitive identification of pseudo-molecular ions, characteristic of reference PFASs. Additionally, principal component analysis (PCA) shows clear discrimination among real samples and reference compounds. Our results show that characteristic molecular ion and fragments peaks can be used to identify PFASs. Furthermore, SIMS two-dimensional (2D) images directly exhibit the distribution of perfluorocarboxylic acid (PFCA) and PFOS in simulated mixtures and real wastewater samples. Such findings indicate that ToF-SIMS is useable to determine PFAS compounds in complex environmental water samples. In conclusion, ToF-SIMS provides simple sample preparation and high sensitivity in mass spectral imaging, offering an alternative solution for environmental forensic analysis of PFASs in wastewater in the future.

Rapid, efficient, and green analytical technique for determination of fluorotelomer alcohol in water by stir bar sorptive extraction

Fluorotelomer alcohols (FTOHs) are one of the major classes of per- and polyfluoroalkyl substances (PFAS). Due to their potential toxicity, persistence, and ubiquitous presence in the environment, some common PFAS are voluntarily phased out; while FTOHs are used as alternatives to conventional PFAS. FTOHs are precursors of perfluorocarboxylic acids (PFCAs) and therefore they are commonly detected in water matrices, which eventually indicate PFAS contamination in drinking water supplies and thus a potential source of human exposure. Even though studies have been conducted nationwide to evaluate the degree of FTOHs in the water environment, robust monitoring is lacking because of the unavailability of simple and sustainable analytical extraction and detection methods. To fill the gap, we developed and validated a simple, rapid, minimal solvent use, no clean-up, and sensitive method for the determination of FTOHs in water by stir bar sorptive extraction (SBSE) coupled with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Three commonly detected FTOHs (6:2 FTOH, 8:2 FTOH, and 10:2 FTOH) were selected as the model compounds. Factors such as extraction time, stirring speed, solvent composition, salt addition, and pH were investigated to achieve optimal extraction efficiency. This "green chemistry" based extraction provided good sensitivity and precision with low method limits of detection ranging from 2.16 ng/L to 16.7 ng/L and with an extraction recovery ranging 55%-111%. The developed method were tested on tap water, brackish water, and wastewater influent and effluent. 6:2 FTOH and 8:2 FTOH were detected in two wastewater samples at 78.0 and 34.8 ng/L, respectively. This optimized SBSE-TD-GC-MS method will be a valuable alternative to investigate FTOHs in water matrices.

Multi-excitation wavelength of gold nanocluster-based fluorescence sensor array for sulfonamides discrimination

Sulfonamides (SAs) are widely used in many fields because of their advantages, including low price, wide antibacterial spectrum, and high stability. However, their accumulation in the human body leads to a variety of serious diseases. Therefore, it is necessary to design a convenient, effective, and sensitive method to detect SAs. Moreover, the fluorescence excitation spectrum has rich information characteristics, especially for the interaction between fluorophore and quencher via various mechanisms. However, the excitation wavelength-guided sensor array construction does not draw proper attention. To address these issues, we used BSA-AuNCs as a single probe to construct a sensor array for the detection of five SAs. The selected SAs showed different quenching effects on the fluorescence intensities of BSA-AuNCs. The changes in the fluorescence intensity at different excitation wavelengths (λ = 230, 250, and 280 nm) have been applied to construct our sensor array and address the distinguishability between the selected SAs. With helping of pattern recognition methods, five different SAs have been identified at three different concentrations. Additionally, qualitative analysis at different moral ratios and quantitative analysis at nanogram concentrations have been considered. Moreover, the proposed sensor array was successfully used to distinguish between different SAs in commercial milk with an accuracy of 100 %. This study provides a simple and powerful approach to SAs detection. Also, it shows a broad application prospect in the field of food and drug monitoring.

Iron-Doped Bimodal Mesoporous Silica Nanomaterials as Sorbents for Solid-Phase Extraction of Perfluoroalkyl Substances in Environmental Water Samples

In this work, sorbets based on UVM-7 mesoporous silica doped with Fe were synthesized and applied to solid-phase extraction of perfluoroalkyl substances from environmental water samples. These emerging pollutants were then determined by liquid chromatography coupled with a mass spectrometry detector. Thus, Fe-UVM-7 mesoporous silica materials with different contents of iron, as well as different pore sizes (by using alkyltrimethilamonium bromide surfactants with different organic tail lengths) were synthesized, and their structure was confirmed for the first time by transmission electron microscopy, nitrogen adsorption–desorption, X-ray diffraction, and Raman spectroscopy. After comparison, Fe50-UVM-7-C₁₂ was selected as the best material for analyte retention, and several extraction parameters were optimized regarding the loading and elution step. Once the method was developed and applied to real matrices, extraction efficiencies in the range of 61–110% were obtained for analytes with C₈–C₁₄ chain length, both perfluoroalkyl carboxylates, and perfluoroalkyl sulfonates. Likewise, limits of detection in the range of 3.0–8.1 ng L⁻¹ were obtained for all target analytes. In the analysis of real well-water samples, no target compounds were detected. Spiked samples were analyzed in comparison to Oasis WAX cartridges, and statistically comparable results were achieved.

Analysis of Dechlorane Plus and related compounds in gull eggs by GC-HRMS using a novel atmospheric pressure photoionization source

Here, a new gas chromatography-atmospheric pressure photoionization-high-resolution mass spectrometry (GC-APPI-HRMS) method combined with selective pressurized liquid extraction (sPLE) has been developed for the selective determination of Dechlorane Plus (DP) and its related compounds in gull egg samples used as a bioindicator of contamination. To the best of our knowledge, this is the first time these compounds have been analyzed by GC-MS using atmospheric pressure photoionization (APPI). Negative ion dopant-assisted APPI using vapors of diethyl ether and a source temperature of 250 °C provided high ionization efficiencies and mass spectra characterized by intense in-source fragment ions as well as the presence of molecular ion and characteristic cluster ions containing oxygen atoms in their chemical structure. This made it possible to improve the selectivity in the determination of these compounds compared to that obtained with traditional GC-MS ion sources. Under optimized conditions, the sPLE GC-APPI-HRMS (Orbitrap) method provided high recoveries (> 91%), good precisions (RSD% < 12%), and low method limits of detection (0.1-3.5 pg g^-1 wet weight). The developed methodology has been applied to the determination of DP and related compounds in eggs of two gull species (L. michahellis and L. audouinii) from several Spanish protected areas. The results obtained showed significant differences in the DP concentration profiles in eggs from different gull breeding locations and between gull species of the same protected area. These results demonstrated the good performance of the GC-APPI-HRMS system to achieve a selective and sensitive determination of DP and related compounds in complex environmental samples.

Characterizing chain-end structures formed during initiation reactions of radical polymerization for MMA-St-BA terpolymer using pyrolysis-gas chromatography/atmospheric pressure chemical ionization high-resolution time-of-flight mass spectrometry

RATIONALE

Analyzing polymer end groups using pyrolysis (Py) gas chromatography/mass spectrometry (GC/MS) in multi-component polymer samples is not an easy task because of the insufficient sensitivity, selectivity, and mass resolution of conventional Py-GC/MS systems.

METHODS

A new Py-GC/MS system using an atmospheric pressure chemical ionization (APCI) source combined with high-resolution time-of-flight mass spectrometry (TOFMS) was used for end-group analysis of a methyl methacrylate (MMA)-styrene (St)-butyl acrylate (BA) terpolymer (P (MMA-St-BA)), which was radically polymerized using 2,2'-azobis(2-methylbutyronitrile) (AMBN) as an initiator.

RESULTS

Five possible pyrolyzates, comprising an AMBN fragment and a monomer unit, formed during the initiation reactions from one of the three types of end groups, were selectively detected and exclusively identified in their respective extracted ion chromatograms for molecule-related ions, such as M⁺ and [M + H]⁺ , with a narrow mass window of ±2 milli m/z units.

CONCLUSIONS

It was demonstrated that Py-APCI-TOFMS is a powerful technique to characterize in detail the complex end groups in multi-component polymer samples, because of the soft ionization nature of APCI and the high mass resolution of TOFMS.

Development of an Atmospheric Pressure Chemical Ionization Interface for GC-MS

A closed atmospheric pressure chemical ionization (APCI) ion source as interface between a gas chromatograph (GC) and a triple quadrupole mass spectrometer (QqQ-MS) was developed. The influence of different ion source conditions, such as humidity, make-up gas flow, and the position of the GC column, were investigated and determined as main factors to increase sensitivity and repeatability of the system. For a performance test under real conditions, the new APCI ion source was used for the determination of plant protection products in commercially available coffee beans from Vietnam. The ionization behavior was investigated and the majority of the analytes were detected as [MH]+, [M]+∙, or as characteristic fragment ions, which have been assigned to ion source fragmentation. The developed GC-MS methods are based on tandem MS (MS/MS) and revealed for the plant protection products limits of detection (LOD) between 1 and 250 pg on column and relative standard derivations for all compounds < 16%. The used ultrasonic solid-liquid extraction yielded recovery rates of approximately 60 to 100%. Residues of herbicide methyl esters, organophosphorus compounds, and organonitrogen compounds have been detected in the analyzed coffee beans.

The overlooked short- and ultrashort-chain poly- and perfluorinated substances: A review

Poly- and perfluorinated substances (PFAS) comprise more than 3000 individual compounds; nevertheless, most studies to date have focused mainly on the fate, transport and remediation of long-chain PFAS (C > 7). The main objective of this article is to provide the first critical review of the peer-reviewed studies on the analytical methods, occurrence, mobility, and treatment for ultra-short-chain PFAS (C = 2-3) and short-chain PFAS (C = 4-7). Previous studies frequently detected ultra-short-chain and short-chain PFAS in various types of aqueous environments including seas, oceans, rivers, surface/urban runoffs, drinking waters, groundwaters, rain/snow, and deep polar seas. Besides, the recent regulations and restrictions on the use of long-chain PFAS has resulted in a significant shift in the industry towards short-chain alternatives. However, our understanding of the environmental fate and remediation of these ultra-short-chain and short-chain PFAS is still fragmentary. We have also covered the handful studies involving the removal of ultra-short and short-chain PFAS and identified the future research needs.

A Cu(II)-anchored unzipped covalent triazine framework with peroxidase-mimicking properties for molecular imprinting-based electrochemiluminescent detection of sulfaquinoxaline

The authors describe a method of electrochemiluminescent quantitation of the antibiotic sulfaquinoxaline (SQX). It relies on the use of a molecularly imprinted polymer and a Cu(II)-anchored unzipped covalent triazine framework (UnZ-CCTF) with excellent dispersibility, electrical conductivity, and peroxidaze-like activity. The framework was prepared by unzipping a covalent triazine framework under retention of basic triazine units. It was morphologically and structurally characterized by a range of instrumental techniques. The excellent peroxidase-mimicking effect of UnZ-CCTF on the electrochemiluminescence of the luminol/H₂O₂ system was exploited to design an ultrasensitive SQX assay with a 1.0-20 pM detection range and a detection limit of 0.76 pM (at 3δ/m). The technique was used for SQX quantitation in spiked milk samples, achieving recoveries of 94.0-104.8%. Graphical abstract Scheme of the sulfaquinoxaline molecularly imprinted electrochemiluminescence sensor based on Cu-anchored unzipped covalent triazine frameworks.

Quantum dot based multiplex fluorescence quenching immune chromatographic strips for the simultaneous determination of sulfonamide and fluoroquinolone residues in chicken samples

Quantum dot based fluorescence quenching immune chromatographic strips for simultaneous determination of sulfonamides and fluoroquinolones.

Upconversion Nanoparticles and Monodispersed Magnetic Polystyrene Microsphere Based Fluorescence Immunoassay for the Detection of Sulfaquinoxaline in Animal-Derived Foods

A novel fluorescence immunoassay for detecting sulfaquinoxaline (SQX) in animal-derived foods was developed using NaYF4:Yb/Tm upconversion nanoparticles (UCNPs) conjugated with antibodies as fluorescence signal probes, and monodisperse magnetic polystyrene microspheres (MMPMs) modified with coating antigen as immune-sensing capture probes for trapping and separating the signal probes. Based on a competitive immunoassay format, the detection limit of the proposed method for detecting SQX was 0.1 μg L(-1) in buffer and 0.5 μg kg(-1) in food samples. The recoveries of SQX in spiked samples ranged from 69.80 to 133.00%, with coefficients of variation of 0.24-25.06%. The extraction procedure was fast, simple, and environmentally friendly, requiring no organic solvents. In particular, milk samples can be analyzed directly after simple dilution. This method has appealing properties, such as sensitive fluorescence response, a simple and fast extraction procedure, and environmental friendliness, and could be applied to detecting SQX in animal-derived foods.

Gas Chromatography/Atmospheric Pressure Chemical Ionization-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Pyrolysis Oil from German Brown Coal

Pyrolysis oil from the slow pyrolysis of German brown coal from Schöningen, obtained at a temperature of 500°C, was separated and analyzed using hyphenation of gas chromatography with an atmospheric pressure chemical ionization source operated in negative ion mode and Fourier transform ion cyclotron resonance mass spectrometry (GC-APCI-FT-ICR-MS). Development of this ultrahigh-resolving analysis method is described, that is, optimization of specific GC and APCI parameters and performed data processing. The advantages of GC-APCI-FT-ICR-MS hyphenation, for example, soft ionization, ultrahigh-resolving detection, and most important isomer separation, were demonstrated for the sample liquid. For instance, it was possible to separate and identify nine different propylphenol, ethylmethylphenol, and trimethylphenol isomers. Furthermore, homologous series of different acids, for example, alkyl and alkylene carboxylic acids, were verified, as well as homologous series of alkyl phenols, alkyl dihydroxy benzenes, and alkoxy alkyl phenols.