Nontarget Mass Spectrometry Reveals New Perfluoroalkyl Substances in Fish from the Yangtze River and Tangxun Lake, China

Since 2010, unknown PFAS discovery has been reported in commercial products, environmental samples, and biological matrices.

“Since 2010 there have been reports of unknown PFAS discovery in commercial products (e.g.aqueous film-forming foams (AFFFs) [29e31], surfactant concentrates [30e33]), in environmental samples (e.g.water [34e39], sediment [38], soil [40], airborne particulate matter [41] and concrete [40]) and in biological matrices (e.g.fish liver [42], polar bear [43] and human serum [44]).”

Some recent discoveries are legacy substances likely present in the environment for more than 40 years already.

“Among such recent contaminant discoveries, some are PFAA-precursors (e.g.perfluorooctaneamido quaternary ammonium salt [32]) that could contribute to environmental PFAA exposure for years to come [45], some are legacy substances likely present in the environment for more than 40 years already (e.g.chlorinated perfluoroether sulfonates [42]), while others are likely new current-use alternatives (e.”

Liu et al. [42] tentatively proposed a new class of perfluorinated N-heterocycles in fish liver with a confidence level of 3.

“For example, despite more than 5000 known PFASs in all available databases, Liu et al. [42] tentatively proposed a new class of perfluorinated N-heterocycles in fish liver with a confidence level of 3.”

TOF, Orbitrap, and FTICR are three HRMS technologies already proven as useful tools in PFAS discovery.

“TOF [29e32,35,39e41], Orbitrap [34,37,38,42] and Fouriertransform ion cyclotron resonance (FTICR) [30] are three HRMS technologies already proven as useful tools in PFAS discovery.”

Substantial direct evidence of unresolved structural isomers from electrochemical fluorination has been observed in some nontarget studies with chromatography, but other studies used infusion which masks isomers for each distinct homologue.

“Substantial direct evidence of such isomers has been observed in some nontarget studies with chromatography [30,31,42] (Table 2), but others used infusion which masks any isomers for each distinct homologue.”

Chromatography can help separate PFAS isomers, thereby maximizing discovery potential and revealing mass spectra of pure compounds.

“Moreover, commercially relevant PFASs are often composed of multiple structural isomers (i.e. with the same exact mass) [5,59], thus the use of chromatography can also help to separate isomers [31,42], thereby maximizing the discovery potential and revealing mass spectra of pure compounds.”

Novel PFAS have been identified by suspected and non-targeted screening of airborne particles, water, sediments and biological samples.

“Novel PFAS have been identified by suspected and non-targeted screening of airborne particles [16], water [17], sediments [17] and biological samples [18,19] (Table 1).”

New classes of PFAS have been identified in the environment and are gaining worldwide attention.

“New classes of PFAS have been identified in the environment and are gaining worldwide attention.”

Identification of novel PFAS in biological samples, including cations and zwitterions, has been initiated in various matrices.

“Furthermore, identification of novel PFAS in biological samples, including cations and zwitterions, has been initiated in various matrices [18].”

In addition to original PFAS, novel PFAS have been detected in biological samples in accordance with the phasing out of original PFAS and a shift toward manufacturing alternatives.

“In addition to original PFAS, novel PFAS have been detected in biological samples in accordance with the phasing out of original PFAS and a shift toward manufacturing alternatives [18,78,80,82,83].”

Over 300 novel PFAS belonging to 10 different classes were discovered in pooled fish liver samples collected in China.

“Discovery of over 300 novel PFAS belonging to 10 different classes in pooled fish liver samples collected in China [18]”

In-source fragmentation flagging scans for anionic PFAS have proved effective in some recent studies.

“In-source fragmentation flagging scans for anionic PFAS have proved effective in some recent studies [18].”

A recent report identified four new classes of PFAS consisting of more than 165 PFAS compounds in pooled fish samples collected downstream from a fluorochemical manufacturing site.

“A recent report identified four new classes of PFAS consisting of more than 165 PFAS compounds in pooled fish samples collected downstream from a fluorochemical manufacturing site [18].”