Quantitative Determination of Perfluorochemicals in Sediments and Domestic Sludge

TLDR

Perfluorochemicals, especially PFOS, are increasingly studied, yet their presence in solid matrices such as sediments and sewage sludge—suspected major sinks—has received limited attention. The authors developed a quantitative LC‑MS/MS method involving liquid solvent extraction, solid‑phase extraction cleanup, and internal‑standard calibration, and applied it in a limited survey of domestic sludge and sediments. The method achieved limits of detection of 0.7–2.2 ng g⁻¹ in sludge and 0.041–0.246 ng g⁻¹ in sediments, revealing PFC concentrations of 5–152 ng g⁻¹ (perfluorocarboxylates) and 55–3370 ng g⁻¹ (PFSA) in sludge, low ng g⁻¹ to sub‑ng g⁻¹ levels in sediments, and precursor compounds often exceeding PFOS.

Abstract

Perfluorochemicals (PFCs) are the subject of increasingly intense environmental research. Despite their detection both in biota and in aqueous systems, little attention has been paid to the possible presence of this class of compounds in solid environmental matrixes. The limited available data indicate that some PFCs such as perfluorooctane sulfonate (PFOS) may strongly sorb to solids, and sewage sludge is widely suspected as a major sink of PFCs entering municipal waste streams. A quantitative analytical method was developed that consists of liquid solvent extraction of the analytes from sediments and sludge, cleanup via solid-phase extraction, and injection of the extracts with internal standards into a high-performance liquid chromatography (HPLC) system coupled to a tandem mass spectrometer (LC/MS/MS). The limits of detections of the method were analyte and matrix dependent, but ranged from 0.7 to 2.2 ng/g and 0.041 to 0.246 ng/g (dry weight) for sludge and sediment, respectively. A demonstration of the method was performed by conducting a limited survey of domestic sludge and sediments. The concentration of PFCs in domestic sludge ranged from 5 to 152 ng/g for total perfluorocarboxylates and 55 to 3370 ng/g for total perfluoroalkyl sulfonyl-based chemicals. Data from a survey of San Francisco Bay Area sediments suggest widespread occurrence of PFCs in sediments at the low ng/g to sub-ng/g level. Furthermore, substances that may be transformed to PFOS, such as 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA) and 2-(N-methylperfluorooctanesulfonamido) acetic acid (N-MeFOSAA), are present in both sediments and sludge at levels often exceeding PFOS.