Abstract
There is a growing concern over a suspected presense of unknown perfluoroaliphatic substances (PFAS) in consumer goods and in the environment. Such unknown substances, possibly with high molecular weight, might be precursors of hazardous or controlled known PFAS. Recent studies confirmed that total organic fluorine (TOF) content often can not be explained by the measured target PFAS. One of the suspected classes of such unknowns are polymers with fluorotelomer alcohol (FTOH) residues in a side chain. In this report we suggest hydrolysis of precursors, as a complementary method to account for the unknown PFAS. It was shown here that hydrolysis allows to preserve structural information on the perlfuorinated parts of the precursors, which can be an advantage for the purpose of accurate risk assessment or source identification. A convenient procedure for hydrolysis with 4% sodium hydroxide in water-methanol mixture (1:9) at 60 °C for 16 h was shown to convert model substances - FTOH acrylate, methacrylate and isobutyrate esters as well as FTOH phenylcarbamate to free FTOHs. Analysis of extracts of textile samples with preliminary hydrolysis and without it showed up to 1300-fold higher level of “hidden” FTOHs.
Highlights
Two methods are available at present for detection of “hidden polyfluoroalkyl substances (PFAS)” e Total Organic Fluorine, total organic fluorine (TOF) and its modification, Extractable Organic Fluorine, EOF (Akhdhara et al, 2019; Dubocq et al, 2019; Loi et al, 2011; Lu et al, 2019; Musijowski et al, 2007; Schellenberger et al, 2019; Schultes et al, 2019; Taniyasu et al, 2015; Tokranov et al, 2019; Yeung et al, 2008, 2009a, 2009b, 2013) and Total Oxidizable Precursors, TOP (Casson et al, 2018; Mumtaz et al, 2019; Houtz et al, 2016; Houtz and Sedlak, 2012; Wang et al, 2020; Zhang et al, 2019)
Polymers with fluorotelomer side-chain have been identified as an important class of hidden PFAS precursors (Herzke et al, 2012)
fluorotelomer alcohol (FTOH) were analyzed by gas chromatography mass-spectrometry (GCeMS) using selected ion monitoring (SIM)
Summary
There are a growing concern and scientific evidence that perand polyfluoroalkyl substances (PFAS) included in monitoring programs are just a small part of the total PFAS burden (OECD 2019; Borg et al, 2017; Casson et al, 2018; Robel et al, 2017). The method has a good potential for quantitative determination of fluorine It results in a complete loss of information on the structure of precursors. In EOF a sample is first extracted with organic solvent followed by TOF analysis of the extract It has a potential of reflecting only organic fluorine, but the completeness of extraction is always under question. TOP is based on mild oxidation of non-fluorinated parts of precursors with conversion to perfluorocarboxylic or perfluorosulfonic acids, with subsequent analysis of those by target PFAS methods (Casson and Chiang, 2018; Mumtaz et al, 2019; Houtz et al, 2016; Houtz and Sedlak, 2012; Wang et al, 2020; Zhang et al, 2019). The purpose of the present work was development of a simple practical method for hydrolysis of FTOH derivatives and testing the method on textile samples
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