Elsevier

Chemosphere

Volume 193, February 2018, Pages 259-269
Chemosphere

Retention performance of three widely used SPE sorbents for the extraction of perfluoroalkyl substances from seawater

https://doi.org/10.1016/j.chemosphere.2017.10.174Get rights and content

Highlights

  • ā€¢

    Sorption characteristics of twelve PFASs on three widely used SPE sorbents at different conditions were investigated.

  • ā€¢

    The best extraction performance was achieved using OasisĀ® HLB and Strataā„¢-X at pH 8 and 50%/100% matrix seawater content.

  • ā€¢

    The best extraction conditions correspond to the natural properties of marine and brackish waters.

  • ā€¢

    Both analyte and sorbent acid-base behavior plays a crucial role in the extraction performance.

Abstract

Some per- and polyfluoroalkyl substances (PFASs) have been detected ubiquitously in the environment. Owing to the polar character conferred by the presence of the carboxylic or sulfonic acid groups and their resistance to degradation, aquatic environments became their major reservoirs, including marine waters. The procedure of PFAS analysis in aqueous matrices consists usually of solid-phase extraction (SPE) followed by high-performance liquid chromatography coupled to tandem mass spectrometry. Moreover, passive sampling approach using various SPE sorbents may be applied. This study deals with the assessment of retention characteristics of a selected group of PFASs in marine water on three sorbent media widely used in SPE or passive sampling techniques. The influence of type of sorbent, matrix pH, salinity and eluent on the PFAS recovery from aquatic samples was investigated. The best overall extraction conditions were found to be at pH 8 and 50%/100% matrix seawater content using OasisĀ® HLB/Strataā„¢-X as SPE sorbents and methanol as eluent. The matrix properties found to be the most appropriate for extraction of investigated PFASs from aqueous samples (i.e., pH and salinity levels) match well the natural properties of marine and brackish waters. Acid-base behavior was found to be the main driver influencing the recovery of PFASs. These research findings can be used to optimize PFAS extraction conditions from aquatic samples and also to develop efficient extraction procedures for multiresidual analyses.

Introduction

Per- and polyfluoroalkyl substances (PFASs) are manmade organic chemicals formed by a carbon backbone where majority or all hydrogen atoms are replaced with fluorine atoms. PFASs comprise a diverse group of molecules of different functionalities and sizes. Owing to unique physico-chemical properties, these substances have been used in many commercial and industrial applications for over 60 years, e. g., as emulsifiers, lubricants, components of fire-fighting foams, stain and soil repellent agents, textiles, electronics, food packaging and detergents (Buck etĀ al., 2011, Kissa, 2001).

During recent years, however, several PFASs have been recognized as ubiquitous environmental contaminants. Some perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonates (PFSAs) have been found routinely in terrestrial, freshwater and marine environments (Buck etĀ al., 2011, Jahnke etĀ al., 2007, Yamashita etĀ al., 2005), wildlife (Giesy and Kannan, 2001, Houde etĀ al., 2011, Houde etĀ al., 2006), food items (Ostertag etĀ al., 2009, PicĆ³ etĀ al., 2011) and humans (Kannan etĀ al., 2004, Vestergren and Cousins, 2009). PFCAs and PFSAs can be released from products following their use (BečanovĆ” etĀ al., 2016) or may originate from environmental transformations of precursor chemicals (e.g., FTOHs, FASAs and their derivatives) (Ellis etĀ al., 2003, Martin etĀ al., 2006). Toxicity and bioaccumulation of longer-chain PFCAs and PFSAs is well documented (Beach etĀ al., 2006, Conder etĀ al., 2008, Lau etĀ al., 2007). Due to their high environmental persistence, toxicity, bioaccumulative potential and global distribution, some PFCAs and PFSAs are priority substances for ecotoxicological research and regulation.

PFCAs and PFSAs are persistent against typical environmental degradation processes. Due to the carboxylic/sulfonic acid groups, they are less volatile and more soluble in water than legacy persistent organic pollutants (POPs) (Ding and Peijnenburg, 2013). As a result, aquatic environment is their major environmental reservoir. Transport to the marine deep waters and burial into sediments were identified as final sinks of the burden of persistent PFASs cycling in the environment (Ahrens, 2011, Prevedouros etĀ al., 2006, Sanchez-Vidal etĀ al., 2015, Yamashita etĀ al., 2008, Zareitalabad etĀ al., 2013). Pioneering work by Yamashita etĀ al. showed widespread occurrence of PFOA and PFOS in global oceans (Yamashita etĀ al., 2008, Yamashita etĀ al., 2005). Several studies have further focused on gathering data on a broader range of PFASs in open ocean waters along global transects (Ahrens etĀ al., 2010, Ahrens etĀ al., 2009, Benskin etĀ al., 2012a, Benskin etĀ al., 2012b, Cai etĀ al., 2012).

Considering the fate of PFASs in the environment, monitoring of those substances in the global oceans and seas is necessary. The analytical procedure of PFAS determination from aqueous matrices consists usually of solid-phase extraction (SPE) followed by high-performance liquid chromatography coupled to tandem mass spectrometry operated in the negative electrospray mode (HPLC/(āˆ’)ESI-MS/MS) or high resolution time-of-flight (TOF)-MS analysis (Ahrens, 2011). The SPE is beneficial for two main reasons: i) since the PFAS concentrations in the marine environment are often in the sub-ng/L range, extraction and pre-concentration of water samples prior instrumental analysis is necessary to enable detection; and ii) SPE works as a clean-up step which decreases the presence of interfering analytes and thus lowers their matrix effects in instrumental analysis (Andrade-Eiroa etĀ al., 2016).

In order to fulfill the increasing scientific and regulatory demand for good quality analytical data regarding the concentrations of PFASs in the marine environment, the use of an efficient SPE technique is necessary. Moreover, there is a growing demand for high-throughput multiresidue methods that can be used to determine, simultaneously, a broad variety of different pollutants (e.g., PFASs, pharmaceuticals, personal care products, currently used pesticides, etc.). Understanding the PFAS behavior on different extraction sorbents under different conditions is, therefore, necessary not only to find the best extraction method for this specific set of compounds, but also to know what extraction performance can be achieved using methods developed for other classes of contaminants. Moreover, better understanding of PFAS-sorbent interaction behavior at different conditions may prove valuable for the design and optimization of polar passive sampling devices that often use SPE sorbents. This is currently accentuated by the Aqua-gaps, a recent initiative aiming at global monitoring of persistent organic pollutants in the aquatic environment using passive sampling (Lohmann etĀ al., 2017).

The aim of the present study is to: i) investigate recovery characteristics of PFASs most commonly detected in the marine environment on three widely used SPE sorbents, i.e., OasisĀ® HLB, OasisĀ® WAX and Strataā„¢-X; and ii) describe the main drivers influencing the retention of PFASs on these SPE sorbents.

Section snippets

Chemicals and materials

All abbreviations used in this study are listed in TableĀ S1. The analytical standards for twelve target compounds (PFPA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFDoDA, PFTrDA, PFBS, PFHxS, PFOS, PFOSA, see TableĀ S2 for detailed description) and nine isotopically-labelled standards (13C2 PFHxA, 13C4 PFOA, 13C5 PFNA, 13C2 PFDA, 13C2 PFUnDA, 13C2 PFDoDA, 18O2 PFHxS, 13C4 PFOS, dMePFOSA, see TableĀ S3 for detailed description) were purchased from Wellington Laboratory Inc. (Guelph, Ontario, Canada). The

Results for QA/QC

Concentrations of PFASs detected in OasisĀ® HLB and Strataā„¢-X procedural blanks (both nĀ =Ā 3) were in most cases eitherĀ <Ā IQL or at least two orders of magnitude lower that the concentrations measured in the spiked samples (TableĀ S4 in the SI). In a few cases the concentrations in blanks were comparable to the values detected in the spiked samples (this concerned several samples from the 2nd elution fraction only). In this case, only values above the blank average plus three times the SD were

Conclusion

This study deals with the sorption characteristics of a selected group of environmentally relevant PFASs on three widely used SPE sorbents (OasisĀ® HLB, OasisĀ® WAX and Strataā„¢-X). The influence of the type of sorbent, matrix pH and salinity and composition of eluent on the PFAS recovery was investigated.

The best overall extraction conditions were found to be at pH 8 and matrix seawater content 50% (brackish waters) and 100% (marine waters) using either OasisĀ® HLB or Strataā„¢-X as extraction

Acknowledgments

This work was financially supported by the National Sustainability Programme of the Czech Ministry of Education, Youth and Sports (LO1214) and the RECETOX research infrastructure (LM2015051).

References (44)

  • N. Yamashita et al.

    Perfluorinated acids as novel chemical tracers of global circulation of ocean waters

    Chemosphere

    (2008)
  • P. Zareitalabad et al.

    Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in surface waters, sediments, soils and wastewater ā€“ a review on concentrations and distribution coefficients

    Chemosphere

    (2013)
  • L. Ahrens

    Polyfluoroalkyl compounds in the aquatic environment: a review of their occurrence and fate

    J.Ā Environ. Monit.

    (2011)
  • L. Ahrens et al.

    Longitudinal and latitudinal distribution of perfluoroalkyl compounds in the surface water of the Atlantic ocean

    Environ. Sci. Technol.

    (2009)
  • ASTM International

    ASTM D1141ā€“d1198(2013), Standard Practice for the Preparation of Substitute Ocean Water. West Conshohocken, PA

    (2013)
  • S.A. Beach et al.

    Ecotoxicological Evaluation of Perfluorooctanesulfonate (PFOS)

    (2006)
  • J.P. Benskin et al.

    Manufacturing origin of perfluorooctanoate (PFOA) in Atlantic and Canadian arctic seawater

    Environ. Sci. Technol.

    (2012)
  • J.P. Benskin et al.

    Perfluoroalkyl acids in the Atlantic and Canadian arctic oceans

    Environ. Sci. Technol.

    (2012)
  • R.C. Buck et al.

    Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins

    Integr. Environ. Assess. Manag.

    (2011)
  • M. Cai et al.

    Occurrence of perfluoroalkyl compounds in surface waters from the North Pacific to the Arctic ocean

    Environ. Sci. Technol.

    (2012)
  • J.M. Conder et al.

    Are PFCAs bioaccumulative? A critical review and comparison with regulatory criteria and persistent lipophilic compounds

    Environ. Sci. Technol.

    (2008)
  • G. Ding et al.

    Physicochemical properties and aquatic toxicity of poly- and perfluorinated compounds

    Crit. Rev. Environ. Sci. Technol.

    (2013)
  • Cited by (25)

    View all citing articles on Scopus
    View full text