Analysis of Perfluorinated Acids at Parts-Per-Quadrillion Levels in Seawater Using Liquid Chromatography-Tandem Mass Spectrometry

TLDR

Perfluorinated acids (PFAs) are a globally relevant class of environmental contaminants, yet measuring sub‑parts‑per‑trillion or parts‑per‑quadrillion concentrations in water is hindered by high procedural and instrumental blank levels. The study aims to develop ultratrace seawater methods that eliminate procedural and instrumental blank contamination, thereby improving limits of quantitation and enabling investigation of the oceans’ role in PFA transport and fate. By identifying and removing blank contamination sources, the authors created a liquid chromatography‑tandem mass spectrometry method that detects PFOS, PFHS, PFBS, PFOA, PFNA, and PFOSA at low picogram‑per‑liter levels in oceanic waters. The analysis revealed PFOA as the predominant PFA in seawater, with PFOS detected at the next highest concentration.

Abstract

Perfluorinated acids (PFAs) and their salts have emerged as an important class of global environmental contaminants. Determination of sub-parts-per-trillion or parts-per-quadrillion concentrations of perfluorinated acids in aqueous media has been impeded by relatively high background levels arising from procedural or instrumental blanks. To understand the role of the oceans in the transport and fate of perfluorinated acids, methods to determine ultratrace levels of these compounds in seawater are needed. In this study, sources of procedural and instrumental blank contamination by perfluorinated acids have been identified and eliminated, to reduce background levels in blanks and thereby improve limits of quantitation. The method developed in this study is capable of detecting perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHS), perfluorobutanesulfonate (PFBS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), and perfluorooctanesulfonamide (PFOSA) at low pg/L levels in oceanic waters. PFOA is the major perfluorinated compound detected in oceanic waters, followed by PFOS. Further studies are being conducted to elucidate the distribution and fate of perfluorinated acids in oceans.