Determination of PFAS in wastewaters and natural waters by solid phase extraction and UHPLC LTQ/Orbitrap MS for assessing occurrence and removals

Abstract

Perfluoroalkyl substances (PFAS) are known as highly fluorinated aliphatic compounds that are used in a wide variety of industrial and consumer products causing devastating effects on human health and environment. Wastewater treatment plants (WWTPs) have been suggested to be a point source for PFAS to the environment due to emission of effluent and sludge. In this study, an analytical method was established and validated for the analysis of 16 PFAS in environmental samples (seawater, lake and wastewater) and bi-distilled water. All samples were filtered after collection and extracted/purified/pre-concentrated by a weak-anion exchange solid-phase extraction (SPE) procedure. Ultra performance liquid chromatography (UPLC) coupled to Orbitrap mass spectrometry (Orbitrap-MS) employing electrospray ionization (ESI) interface operated in negative mode was used for the quantitative determination of these contaminants. The method was validated in all aqueous matrices with very good linearity (R2 > 0.99), recoveries (60–110%, for most of the compounds), detection/quantification limits (at ng L−1 scale), process efficiency (43%–119%), expanded measured uncertainty (<32%) and precision (<20%). After evaluation, the presented fully elaborated workflow was applied to real samples for determining dissolved phase concentrations from secondary influent and secondary, tertiary effluent of WWTP of Ioannina city (Greece) and from the secondary effluent of a hospital WWTP as well as samples from the lake Pamvotis located in Ioannina and samples from Ionian Sea. The most abundant PFAS in all the types of water was Perfluorooctanesulfonamide (PFOSA) and Perfluoro-n-octanoic acid (PFOA) with concentrations up to 21 ng L−1 (secondary influent) and 160 ng L−1 (hospital influent), respectively. This study showed that PFAS with high chain (C8–C13) contribute up to ∼ 38.5% to the total concentration of PFAS in secondary influent of municipal and hospital wastewaters. An average removal efficiency of ∑PFAS was observed at 60% in secondary treatment, with maximum average efficiencies being up to 80% in tertiary treatment. Finally, the concentrations of PFAS in sea and lake samples were generally non-detectable or lower than those detected in wastewaters.