Disposition of Fluorine on New Firefighter Turnout Gear.

Firefighter turnout gear is essential for reducing occupational exposure to hazardous chemicals during training and fire events. Per-and polyfluoroalkyl substances (PFASs) are observed in firefighter serum, and possible occupational sources include the air and dust of fires, aqueous film-forming foam, and turnout gear. Limited data exist for nonvolatile and volatile PFASs on firefighter turnout gear and the disposition of fluorine on the individual layers of turnout gear. Further implications for exposure to fluorine on turnout gear are not well understood. Three unused turnout garments purchased in 2019 and one purchased in 2008, were analyzed for 50 nonvolatile and 15 volatile PFASs by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF-MS) and gas chromatography-mass spectrometry (GC-MS), respectively. Particle-induced gamma ray emission (PIGE), a surface technique, and instrumental neutron activation analysis (INAA), a bulk technique, were used to measure total fluorine. Bulk characterization of the layers by pyrolysis-GC/MS (py-GC/MS) was used to differentiate fluoropolymer (e.g., PTFE) films from textile layers finished with side-chain polymers. The outer layer, moisture barrier, and thermal layers of the turnout gear all yielded measured concentrations of volatile PFASs that exceeded nonvolatile PFAS concentrations, but the summed molar concentrations made up only a small fraction of total fluorine (0.0016-6.7%). Moisture barrier layers comprised a PTFE film, as determined by py-GC-MS, and gave the highest individual nonvolatile (0.159 mg F/kg) and volatile PFAS (20.7 mg F/kg) as well as total fluorine (122,000 mg F/kg) concentrations. Outer and thermal layers comprised aromatic polyamide-based fibers (aramid) treated with side-chain fluoropolymers and had lower levels of individual nonvolatile and volatile PFASs. Equal concentrations of total fluorine by both PIGE and INAA on the outer and thermal layers is consistent with treatment with a side-chain fluoropolymer coating. New turnout gear should be examined as a potential source of firefighter occupational exposure to nonvolatile and volatile PFASs in future assessments.

Reactive Desorption Electrospray Ionization Mass Spectrometry To Determine Intrinsic Degradability of Poly(lactic-co-glycolic acid) Chains.

Because of its speed, sensitivity, and ability to scrutinize individual species, mass spectrometry (MS) has become an essential tool in analytical strategies aimed at studying the degradation behavior of polyesters. MS analyses can be performed prior to the degradation event for structural characterization of initial substrates or after it has occurred to measure the decreasing size of products as a function of time. Here, we show that MS can also be usefully employed during the degradation process by online monitoring the chain solvolysis induced by reactive desorption electrospray ionization (DESI). Cleavage of ester bonds in random copolymers of lactic acid (LA) and glycolic acid (GA) was achieved by electrospraying methanol-containing NaOH onto the substrates. Experimental conditions were optimized to generate methanolysis products of high abundance so that mass spectra can be conveniently processed using Kendrick-based approaches. The same reactive-DESI performance was demonstrated for two sample preparations, solvent casting for soluble samples or pressed pellets for highly crystalline substrates, permitting to compare polymers with LA/GA ratios ranging from 100/0 to 5/95. Analysis of sample fractions collected by size exclusion chromatography showed that methanolysis occurs independently of the original chain size, so data recorded for poly(LA-co-GA) (PLAGA) copolymers with the average molecular weight ranging from 10 to 180 kDa could be safely compared. The average mass of methanolysis products was observed to decrease linearly (R2 = 0.9900) as the GA content increases in PLAGA substrates, consistent with the susceptibility of ester bonds toward solvolysis being higher in GA than in LA. Because DESI only explores the surface of solids, these data do not reflect bulk degradability of the copolymers but, instead, their relative degradability at the molecular level. Based on a "reactive-DESI degradability scale" such as that established here for PLAGA, the proposed method offers interesting perspectives to qualify intrinsic degradability of different polyesters and evaluate their erosion susceptibility or to determine the degradability of those polymers known to degrade via erosion only.

Rapid Fingerprinting of High-Molecular-Weight Polymers by Laser Desorption-Ionization Using Through-Hole Alumina Membrane High-Resolution Mass Spectrometry.

Residual acid found in the desorption ionization using through-holes alumina membranes (DIUTHAME) induces a reproducible protonation/in-source dissociation of polymers made of ester, amide, or siloxane moieties during their surface-assisted laser desorption ionization (SALDI) mass analysis. Deposited on the DIUTHAME chips in solution (solvent-based) or in pure form by melting the polymer powder in situ (solvent-free), high-molecular-weight nylons, silicone, or functionalized celluloses among other polymers are instantly fingerprinted by laser DIUTHAME high-resolution mass spectrometry (MS) with specific patterns resembling their direct analysis in real-time (DART) single-stage or tandem mass spectra. Depending on the polymer, two main types of fingerprints are observed with either the protonated monomer or product ions revealing the nature of the repeating unit or its functionalization. This technique allows a rapid molecular analysis of industrial homopolymers regardless of their molecular weight and complementary to DART with simple or no sample preparation and also promisingly applicable for copolymers.

An arsenal of tools based on Kendrick mass defects to process congested electrospray ionization high-resolution mass spectra of polymers with multiple charging.

RATIONALE: Electrospray ionization (ESI) favors the multiple charging of high molecular weight polymer samples and allows their high-resolution mass analysis in the low-mass range. It also induces the detection of numerous ion series at different charge states with different adducts complicating the interpretation of the mass spectrum which should be facilitated by an appropriate data processing. METHODS: An arsenal of tools based on the Kendrick mass defect (KMD) is proposed to process congested ESI high-resolution mass spectra of poly(propylene oxide) (PPO) samples. The combination of regular, charge-dependent, and resolution-enhanced KMD plots in addition to a "remainders" plot and a new three-dimensional plot offers unrivaled capabilities of filtering for any minor series among thousands of points. The sequential data processing is conducted using Kendo, a spreadsheet developed in-house for an advanced KMD analysis. RESULTS: The charge-state distribution is easily evaluated by counting the parallel lines in a regular KMD plot. A charge-dependent resolution-enhanced KMD plot instantly reveals the variation of adducted ions at a given charge state, helping the user to choose the best analytical conditions. Ion series at different charge states from PPO oligomers carrying different end-groups are also efficiently extracted using several combinations of KMD and remainders plots and assigned using a new simulator tool. CONCLUSIONS: The innovative combination of existing and new KMD-related plots, selection tools, and simulator all combined in a single spreadsheet dramatically facilitates the processing and interpretation of complex ESI mass spectral data. The presented tools may be extended to any other class of homo-, co- and terpolymers.

Thermal desorption and pyrolysis direct analysis in real time mass spectrometry for qualitative characterization of polymers and polymer additives.

RATIONALE: Direct analysis in real time mass spectrometry (DART-MS) provides qualitative information about additives and polymer composition. However, the observed mass spectra are dependent on sampling conditions, in particular the DART gas temperature. This report describes the combination of a heated sample stage with DART-MS for polymer characterization. METHODS: Industrial polymers with different compositions were examined by thermal desorption and pyrolysis (TDPy) DART. Samples were heated on disposable copper stages from ambient temperature to 600°C, and the evolved gases were introduced directly into a DART ion source through a glass tee. Time- and temperature-dependent mass spectra were acquired using a high-resolution time-of-flight mass spectrometer. Kendrick mass analysis was applied to the interpretation of complex mass spectra observed for fluorinated polymers. RESULTS: Positive-ion DART mass spectra of common polymers exhibited peak series differing by monomer masses, often accompanied by a peak corresponding to the protonated monomer. Even polymers that did not exhibit a clear series of peaks produced characteristic mass spectra. Positive-ion and negative-ion mass spectra were recorded for fluorinated polymers, with polytetrafluoroethylene (PTFE) producing only negative ions. Thermal desorption provided characteristic temperature profiles for volatile species such as polymer additives and polymer pyrolysis products. CONCLUSIONS: In comparison with direct analysis by positioning sample directly in the heated DART gas stream, TDPy DART provides a more versatile sampling method and provides thermal separation and profiling of polymer additives, intact short polymer chains, and pyrolysis fragments.

Base-catalyzed C-alkylation of potassium enolates with styrenes via a metal-ene reaction: a mechanistic study.

Base-catalyzed, C-alkylation of potassium (K) enolates with styrenes (CAKES) has recently emerged as a highly practical and convenient method for elaboration or synthesis of pharmaceutically-relevant cores. K enolate-type precursors such as alkyl-substituted heterocycles (pyridines, pyrazines and thiophenes), ketones, imines, nitriles and amides undergo C-alkylation reactions with styrene in the presence of KOtBu or KHMDS. Surprisingly, no studies have probed the reaction mechanism beyond the likely initial formation of a K enolate. Herein, a synergistic approach of computational (DFT), kinetic and deuterium labelling studies rationalizes various experimental observations and supports a metal-ene-type reaction for amide CAKES. Moreover, our approach explains experimental observations in other reported C-alkylation reactions of other enolate-type precursors, thus implicating a general mechanism for CAKES.

Correction: Base-catalyzed C-alkylation of potassium enolates with styrenes via a metal-ene reaction: a mechanistic study.

Correction for 'Base-catalyzed C-alkylation of potassium enolates with styrenes via a metal-ene reaction: a mechanistic study' by Joshua P. Barham et al., Org. Biomol. Chem., 2020, DOI: 10.1039/c9ob02495f.

Well-organised two-dimensional self-assembly controlled by in situ formation of a Cu(II)-coordinated rufigallol derivative: a scanning tunnelling microscopy study.

The two-dimensional self-assembly of rufigallol derivatives and their metal coordination were studied by scanning tunnelling microscopy. Ex situ Cu(II)-coordinated rufigallol derivatives exhibited columnar structures with some defects, whereas regular and linear structures were formed upon in situ metal coordination at solid/liquid interfaces.

Mass Spectrometry-Based Analytical Strategy for Comprehensive Molecular Characterization of Biodegradable Poly(lactic-co-glycolic Acid) Copolymers.

An analytical methodology with mass spectrometry as the core technique was developed for precise characterization of end groups, size, and co-monomeric composition of poly(lactic-co-glycolic acid) (PLGA) copolymers, as a preliminary step to qualify their biodegradability. Four PLGA samples were studied, with GA molar content varying from 0 to 50% and Mw ranging from 18 to 75 kg mol-1 according to the supplier. Size exclusion chromatography (SEC) and liquid state nuclear magnetic resonance (NMR) were used as either complementary or validation techniques. As confirmed by tandem mass spectrometry (MS/MS) experiments, macrocycles were most prominent in the low mass range. Nevertheless, elemental compositions derived from high resolution (HR) mass measurements of linear species were consistent with chain terminations revealed by NMR. Off-line coupling of SEC with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) permitted calibration curves to be built based on absolute molecular weights and, although slightly overestimated, so-obtained Mn and Mw values compared well with SEC and NMR results. Homogeneity of the co-monomeric content of all chains within each PLGA sample was demonstrated using surface-assisted laser desorption/ionization in a reactive mode (reactive-SALDI), a newly developed technique that takes advantage of residual acid on desorption ionization using through-hole alumina membrane (DIUTHAME) chips to induce dissociation of high-molecular-weight polymers containing cleavable C-O bonds. All HRMS data were best handled with Kendrick analysis, which helped reveal minor species and allowed automated computation of congested mass spectra.

Simple Pretreatment for the Analysis of Additives and Polymers by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Using a Through-Hole Alumina Membrane as a Functional Substrate.

The analysis of additives and polymers was performed by desorption ionization using through-hole alumina membrane (DIUTHAME) as a functional substrate for both sample pretreatment and surface-assisted laser desorption/ionization (SALDI) mass spectrometry. Using the unique absorbing/filtering capabilities of DIUTHAME and investigating the solubility of analytes/bulk materials in some solvents, three pretreatment techniques were demonstrated with (1) the selective removal of hydrophilic poly(ethylene oxide) (PEO)-based components from a "PEO-monostearate" sample, (2) the on-chip filtration of solubilized decabromodiphenylether (DBDE) from a solution of polystyrene that had been preliminarily precipitated, and (3) the on-chip extraction of antioxidants (Irganox 1010, Irgafos 168, and dimyristyl 3,3'-thiodipropionate) from a suspension of polypropylene powder or from the powder itself. The extracted analytes were further mass-analyzed using a spiral high-resolution time-of-flight analyzer to assess their elemental composition or molecular distribution.

The Kendrick analysis for polymer mass spectrometry.

The mass spectrum of a polymer often displays repetitive patterns with peak series spaced by the repeating unit(s) of the polymeric backbones, sometimes complexified with different adducts, chain terminations, or charge states. Exploring the complex mass spectral data or filtering the unwanted signal is tedious whether performed manually or automatically. In contrast, the now 60-year-old Kendrick (mass defect) analysis, when adapted to polymer ions, produces visual two-dimensional maps with intuitive alignments of the repetitive patterns and favourable deconvolution of features overlaid in the one-dimensional mass spectrum. This special feature article reports on an up-to-date and theoretically sound use of Kendrick plots as a data processing tool. The approach requires no prior knowledge of the sample but offers promising dynamic capabilities for visualizing, filtering, and sometimes assigning congested mass spectra. Examples of applications of the approach to polymers are discussed throughout the text, but the same tools can be readily extended to other applications, including the analysis of polymers present as pollutants/contaminants, and to other analytes incorporating a repetitive moiety, for example, oils or lipids. In each of these instances, data processing can benefit from the application of an updated and interactive Kendrick analysis.

On the Kendrick Mass Defect Plots of Multiply Charged Polymer Ions: Splits, Misalignments, and How to Correct Them.

The Kendrick mass defect (KMD) analysis of multiply charged polymeric distributions has recently revealed a surprising isotopic split in their KMD plots-namely a 1/z difference between KMDs of isotopes of an oligomer at charge state z. Relying on the KMD analysis of actual and simulated distributions of poly(ethylene oxide) (PEO), the isotopic split is mathematically accounted for and found to go with an isotopic misalignment in certain cases. It is demonstrated that the divisibility (resp. indivisibility) of the nominal mass of the repeating unit (R) by z is the condition for homolog ions to line up horizontally (resp. misaligned obliquely) in a KMD plot. Computing KMDs using a fractional base unit R/z eventually corrects the misalignments for the associated charge state while using the least common multiple of all the charge states as the divisor realigns all the points at once. The isotopic split itself can be removed by using either a new charge-dependent KMD plot compatible with any fractional base unit or the remainders of KM (RKM) recently developed for low-resolution data all found to be linked in a unified theory. These original applications of the fractional base units and the RKM plots are of importance theoretically to satisfy the basics of a mass defect analysis and practically for a correct data handling of single stage and tandem mass spectra of multiply charged homo- and copolymers. Graphical Abstract ᅟ.