Discovery of C₅–C₁₇ Poly- and Perfluoroalkyl Substances in Water by In-Line SPE-HPLC-Orbitrap with In-Source Fragmentation Flagging

Abstract

The presence of unknown organofluorine compounds in environmental samples has prompted the development of nontargeted analytical methods capable of detecting new perfluoroalkyl and polyfluoroalkyl substances (PFASs). By combining high volume injection with high performance liquid chromatography (HPLC) and ultrahigh resolution Orbitrap mass spectrometry, a sensitive (0.003-0.2 ng F/mL for model mass-labeled PFASs) untargeted workflow was developed for discovery and characterization of novel PFASs in water. In the first step, up to 5 mL of water is injected to in-line solid phase extraction, chromatographed by HPLC, and detected by electrospray ionization with mass spectral acquisition in parallel modes cycling back and forth: (i) full scan with ultrahigh resolving power (RP = 120,000, mass accuracy ≤3 ppm), and (ii) in-source fragmentation flagging scans designed to yield marker fragment ions including [C2F5](-) (m/z 118.992), [C3F7](-) (m/z 168.988), [SO4H](-) (m/z 96.959), and [Cl](-) (m/z 34.9). For flagged PFASs, plausible empirical formulas were generated from accurate masses, isotopic patterns, and fragment ions. In the second step, another injection is made to collect high resolution MS/MS spectra of suspect PFAS ions, allowing further confirmation of empirical formulas while also enabling preliminary structural characterization. The method was validated by applying it to an industrial wastewater, and 36 new PFASs were discovered. Of these, 26 were confidently assigned to 3 new PFAS classes that have not previously been reported in the environment: polyfluorinated sulfates (CnFn+3Hn-2SO4(-); n = 5, 7, 9, 11, 13, and 15), chlorine substituted perfluorocarboxylates (ClCnF2nCO2(-); n = 4-11), and hydro substituted perfluorocarboxylates (HCnF2nCO2(-); n = 5-16). Application of the technique to environmental water samples is now warranted.

PFASs in the Nordic environment

“…Improvement and lower costs of advanced mass spectrometric (MS) instruments such as quadrupole time-of-flight (qToF) and Orbitrap in combination with ultra-high performance liquid chromatography (UHPLC) allows to apply high accuracy and high resolution chromatography in combination with high resolution MS (HRMS) for the unequivocal determination of PFASs in environmental samples (Wille et al, 2010). These techniques have also been applied for the quantitative identification of novel PFASs (Xiao, 2017, Liu et al, 2015, Yu et al, 2018, Newton et al, 2017, Fakouri Baygi et al, 2016, Strynar et al, 2015, Ruan and Jiang, 2017. However, data analysis and quality control of these advanced screening methods are usually very time consuming and quantification of new compounds might be uncertain if no suitable standards are available.…”

Hundreds of Unrecognized Halogenated Contaminants Discovered in Polar Bear Serum

“…A polyethersulfone stir bar-assisted sorptive method was developed for sample extraction and a non-target high resolution mass spectrometry (Nt-HRMS) method [6] coupled to HPLC was used for unknown discovery. A controlled mouse study, where mice were exposed to a PCB-mixture or vehicle control [7] , was then performed to confirm the novel PCB metabolites discovered in polar bears.…”

Identifying Per- and Polyfluorinated Chemical Species with a Combined Targeted and Non-Targeted-Screening High-Resolution Mass Spectrometry Workflow

“…For PFAS analysis, multiple solid retentive phases including non-polar, functionalized polar, and ion exchange columns have been used to varying extents for subclasses of fluorinated species in a wide variety of matrices 9,12,13,14,15,16 . Advances in SPE sample analysis using on-line setups greatly increase the throughput of the approach and improve the reproducibility of sample handling, but the fundamental process remains consistent 17 . Some efforts to remove the offline concentration of SPE using large volume injections have also been undertaken, but these require modifications to the chromatography that place them outside the realm of casual analysis 18,19 .…”