Practical application guide for the discovery of novel PFAS in environmental samples using high resolution mass spectrometry.

BACKGROUND: The intersection of the topics of high-resolution mass spectrometry (HRMS) and per- and polyfluoroalkyl substances (PFAS) bring together two disparate and complex subjects. Recently non-targeted analysis (NTA) for the discovery of novel PFAS in environmental and biological media has been shown to be valuable in multiple applications. Classical targeted analysis for PFAS using LC-MS/MS, though growing in compound coverage, is still unable to inform a holistic understanding of the PFAS burden in most samples. NTA fills at least a portion of this data gap. OBJECTIVES: Entrance into the study of novel PFAS discovery requires identification techniques such as HRMS (e.g., QTOF and Orbitrap) instrumentation. This requires practical knowledge of best approaches depending on the purpose of the analyses. The utility of HRMS applications for PFAS discovery is unquestioned and will likely play a significant role in many future environmental and human exposure studies. METHODS/RESULTS: PFAS have some characteristics that make them standout from most other chemicals present in samples. Through a series of tell-tale PFAS characteristics (e.g., characteristic mass defect range, homologous series and characteristic fragmentation patterns), and case studies different approaches and remaining challenges are demonstrated. IMPACT STATEMENT: The identification of novel PFAS via non-targeted analysis using high resolution mass spectrometry is an important and difficult endeavor. This synopsis document will hopefully make current and future efforts on this topic easier to perform for novice and experienced alike. The typical time devoted to NTA PFAS investigations (weeks to months or more) may benefit from these practical steps employed.

Chitosan from crab shell waste for soft lithography of bioplastic diffraction gratings.

Bioplastic diffraction gratings are fabricated from chitosan prepared from crab shells through a soft lithography replication process. Atomic force microscopy and diffraction experiments with the chitosan grating replicas indicate the successful copying of periodic nanoscale groove structures corresponding to densities of 600 and 1200 lines/mm. First-order efficiency of bioplastic gratings is comparable to the output of elastomeric grating replicas.

Comparative proteomics reveals anticancer compounds from Lansium domesticum against NSCLC cells target mitochondrial processes.

Lansium domesticum is identified as a potential source of anticancer compounds. However, there are minimal studies on its anti-lung cancer properties as well as its mechanism of action. Here, we show the specificity of lanzones hexane (LH) leaf extracts to non-small cell lung cancer cells (A549) compared to normal lung fibroblast cells (CCD19-Lu) and normal epithelial prostate cells (PNT2). Subsequent bioassay-guided fractionation of the hexane leaf extracts identified two bioactive fractions with IC50 values of 2.694 µg/ml (LH6-6) and 2.883 µg/ml (LH7-6). LH 6-6 treatment (1 µg/ml concentration) also showed a significantly reduced migration potential of A549 relative to the control. Thirty-one phytocompounds were isolated and identified using gas chromatography-mass spectrometric (MS) analysis and were then subjected to network pharmacology analysis to assess its effects on lung cancer target proteins. Using liquid chromatography-tandem mass spectrometry proteomics experiments, we were able to show that these compounds cause cytotoxic effects through targeting mitochondrial processes in A549 lung cancer cells.

Trace organic chemical pollutants from the lake waters of San Pablo City, Philippines by targeted and non-targeted analysis.

More than half of the freshwater lakes in the Philippines are small with surface areas of <2 km2. The dynamics in these lakes are different from those in the bigger lakes. This study was conducted to determine the organic pollutants and their sources in three of the seven lakes of San Pablo City in Laguna, Philippines: lakes Palakpakin, Sampaloc, and Pandin. Gas Chromatography-Mass Spectrometry (GC-MS) and Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS) were used in the targeted and non-targeted analysis of the lake water samples. The three lakes are all volcanic crater lakes but are exposed to different anthropogenic activities, which includes domestic activities, livelihood (farming and aquaculture) and eco-tourism. Due to the presence of rice fields and fruit plantations, chlorpyrifos was detected in the three lakes while other pesticides like cypermethrin, picolinafen and quinoxyfen were additionally found in Lake Sampaloc, which is the biggest of the three lakes and located within the urbanized section of the city. Traces of different surfactants (linear alkylbenzene sulfonates, secondary alkyl sulfonates, alkyl sulfates, alkyl ether sulfates), biocide benzalkonium chloride, insect repellent diethyltoluamide, antibiotics (sulfadiazine and sulfamethoxazole), hypertension drug telmisartan, phosphate-based fire retardants, and artificial sweeteners (acesulfame, cyclamate, saccharin and sucralose) were detected in lakes Sampaloc and Palakpakin. The same surfactants, artificial sweeteners, insect repellant and phosphate-based fire retardants were also found in Lake Pandin, which is mainly used for eco-tourism activities like swimming and boating. The results of this study suggest that the organic pollutants present in the small lakes can be linked to the various human activities in the immediate lake environment. Because small lakes are more prone to environmental stresses, human activities in the said lakes must be regulated to ensure sustainable development.

Sampling and simultaneous determination of volatile per- and polyfluoroalkyl substances in wastewater treatment plant air and water.

Volatile per- and polyfluoroalkyl substances (PFASs) are often used as precursors in the synthesis of nonvolatile PFASs. The volatile PFASs, which include the perfluoroalkyl iodides (PFAIs), fluorotelomer iodides (FTIs), fluorotelomer alcohols (FTOHs), fluorotelomer olefins (FTOs), fluorotelomer acrylates (FTACs), and fluorotelomer methacrylates (FTMACs), are often produced starting from the telomerization process. These volatile compounds can be present in the air and water environment and can be transformed into highly persistent perfluoroalkyl carboxylic acids. With the exception of FTOHs, which are well studied, the determination of other volatile PFASs is also of prime importance in studying the sources and fate of PFASs. In this study, a method was developed to determine representative precursor compounds that included PFAIs, FTIs, FTOs, FTACs, and FTMACs in wastewater treatment plant (WWTP) air and water samples. The sampling and sample preparation step involved the use of solid-phase extraction (SPE) cartridges with HLB™ material to enrich the analyte. Gas chromatography with mass spectrometry was employed for the detection and quantification of the analytes. Method validation results showed high linearity and sensitivity in the positive electron ionization-selected ion monitoring mode (+EI-SIM). The absolute instrumental limits of detection were in the range of 0.5 to 2 pg. The method detection limit (MDL) in air was 1 ng/m3 with the exception of the FTACs which could be only be detected at concentrations higher than 40 ng/m3. The MDL in water was 10 ng/L. Direct spiking of the cartridges and analyte introduction by volatilization from the glass surface onto the SPE material had recoveries between 86 and 100%. The volatile PFASs were shown to readily partition into the air rather than into water. Consequently, large losses in the amount of PFASs were observed when these were spiked into the water. Graphical abstract Wastewater treatment plant air and water samples were passed through HLB™ solid-phase materials. The eluates were injected onto a GC-MS system to simultaneously determine the volatile PFASs.

Characterization of 3-Aminopropyl Oligosilsesquioxane.

The synthesis routes in the production of polysilsesquioxanes have largely relied upon in situ formations. This perspective often leads to polymers in which their basic structures including molecular weight and functionality are unknown [ Lichtenhan , J. D. ; et al. Silsesquioxane-siloxane copolymers from polyhedral silsesquioxanes Macromolecules , 1993 , 26 , 2141 - 2142 , http://dx.doi.org/10.1021/ma0060a053 ]. For a better understanding of the polysilsesquioxane properties and applications, there is a need to develop more techniques to enable their chemical characterization. An innovative method was developed to determine the molecular weight distribution (MWD) of an oligosilsesquioxane synthesized in-house from (3-aminopropyl)triethoxysilane. This method, which can be applied to other silsesquioxanes, siloxanes, and similar oligomers and polymers, involved separation using high performance liquid chromatography (HPLC) and detection using mass spectrometry (MS) with electrospray ionization (ESI). The novelty of the method lies on the unique determination of the absolute concentrations of the individual homologues present in the sample formulation. The use of absolute concentrations is necessary in estimating the MWD of the formulation when relative percentage, which is based solely on mass spectral ion intensities, becomes irrelevant due to the disproportionate response factors of the homologues. Determination of absolute concentration requires the use of single-homologue calibration standards. Because of commercial unavailability, these standards were prepared by efficient fractionation of the original formulation.

High Resolution Mass Spectrometry of Polyfluorinated Polyether-Based Formulation.

High resolution mass spectrometry (HRMS) was successfully applied to elucidate the structure of a polyfluorinated polyether (PFPE)-based formulation. The mass spectrum generated from direct injection into the MS was examined by identifying the different repeating units manually and with the aid of an instrument data processor. Highly accurate mass spectral data enabled the calculation of higher-order mass defects. The different plots of MW and the nth-order mass defects (up to n = 3) could aid in assessing the structure of the different repeating units and estimating their absolute and relative number per molecule. The three major repeating units were -C2H4O-, -C2F4O-, and -CF2O-. Tandem MS was used to identify the end groups that appeared to be phosphates, as well as the possible distribution of the repeating units. Reversed-phase HPLC separated of the polymer molecules on the basis of number of nonpolar repeating units. The elucidated structure resembles the structure in the published manufacturer technical data. This analytical approach to the characterization of a PFPE-based formulation can serve as a guide in analyzing not just other PFPE-based formulations but also other fluorinated and non-fluorinated polymers. The information from MS is essential in studying the physico-chemical properties of PFPEs and can help in assessing the risks they pose to the environment and to human health. Graphical Abstract ᅟ.

Degree of deacetylation of chitosan by infrared spectroscopy and partial least squares.

The determination of the degree of deacetylation of highly deacetylated chitosan by infrared (IR) spectroscopy was significantly improved with the use of partial least squares (PLS). The IR spectral region from 1500 to 1800 cm(-1) was taken as the dataset. Different PLS models resulting from various data pre-treatments were evaluated and compared. The PLS model that gave excellent internal and external validation performance came from the data that were corrected for the baseline and that was normalized relative to the maximum corrected absorbance. Analysis of the PLS loadings plot showed that the important variables in the spectral region came from the absorption maxima related to the amide bands at 1660 and 1550 cm(-1) and amine band at 1600 cm(-1). IR-PLS results were comparable to the results obtained by potentiometric titration. IR-PLS results were found to be more precise and rugged compared to the usual IR absorbance ratio method. This is consistent with the fact that IR spectral resolution is not really high and that the absorption at a single wavelength is influenced by other factors like hydrogen bonding and the presence of water.

The interaction of chitosan and olive oil: effects of degree of deacetylation and degree of polymerization.

The combined effects of degree of deacetylation (DD) and degree of polymerization (DP) on the ability of chitosan to interact with olive oil was studied. The oil-binding test, a method that makes use of olive oil as a representative fat, was adopted as a measure of the interaction of chitosan and olive oil. The oil-binding capacities of twelve chitosan samples with DPs ranging from 470 to 1450 and DDs of 75% to 95% were determined. The oil-binding capacities were then correlated to the DD and DP using partial least squares (PLS) regression. The generated PLS model had a root mean square error of prediction (RMSEP) of 9.1%. Results indicated that oil-binding capacity is a function of DD more than of DP. For chitosan with DD at the interval 50%90%, the observed deviation from the linear correlation increased. In this interval, free fatty acid anions facilitate the interaction of chitosan and olive oil. Free fatty acids form a stable ionic interaction with the former and a strong hydrophobic interaction with the latter.