Simultaneous determination of eighteen perfluorinated compounds in dissolved and particulate phases of wastewater, and in sewage sludge by liquid chromatography-tandem mass spectrometry

Abstract

Perfluorinated compounds (PFCs) are known chemicals that are used in a wide variety of industrial and consumer products, and have been reported to exist in the environment as contaminants. In this study, a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) method was developed for simultaneous determination of 10 perfluoroalkyl carboxylate acids (PFCAs), 5 perfluoroalkyl sulfonates (PFASs), and 3 perfluoroalkyl sulfonamides (PFSAs) (18 PFCs in total), in dissolved and particulate phases of wastewater (raw and treated), and in dewatered sewage sludge. The target PFCAs were perfluoropentanoic acid (PFPeA; C5), perfluorohexanoic acid (PFHxA; C6), perfluoroheptanoic acid (PFHpA; C7), perfluorooctanoic acid (PFOA; C8), perfluorononanoic acid (PFNA; C9), perfluorodecanoic acid (PFDA; C10), perfluoroundecanoic acid (PFUdA; C11), perfluorododecanoic acid (PFDoA; C12), perfluorotridecanoic acid (PFTrDA; C13), and perfluorotetradecanoic acid (PFTeDA; C14). The target PFASs were potassium perfluorobutanesulfonate (PFBS; C4), sodium perfluorohexanesulfonate (PFHxS; C6), sodium perfluoroheptanesulfonate (PFHpS; C7), sodium perfluorooctanesulfonate (PFOS; C8), and sodium perfluorodecanesulfonate (PFDS; C10), and the target PFSAs were perfluorooctane sulfonamide (PFOSA), N-methylperfluorooctane sulfonamide (N-MeFOSA), and N-ethylperfluorooctane sulfonamide (N-EtFOSA). Wastewater samples were filtered after collection and extracted/purified/pre-concentrated by a solid-phase extraction (SPE) procedure. Particulate matter and sludge samples were extracted by a liquid–solid extraction (LSE) and ultra-sonication procedure, and thereafter purified/preconcentrated by the same SPE procedure that was followed for the dissolved phase of wastewater. The internal standards, perfluoro-n-[1,2,3,4-¹³C₄]octanoic acid (¹³C₄-PFOA), sodium perfluoro-1-[1,2,3,4-¹³C₄]octanesulfonate (¹³C₄-PFOS), and N-methyl-d₃-perfluoro-1-octanesulfonamide (²D₃-N-MeFOSA) provided adequate compensation for variations in the extraction percentages and instrumental response. The limits of quantification (LOQs) ranged from 0.29 (PFHpS) to 3.0 ng L⁻¹ (PFDoA) for dissolved phase samples, and from 0.15 (PFHpS) to 1.5 ng g⁻¹ dry weight (dw) (PFDoA) for particulate matter and sludge samples. The developed methods were applied successfully to wastewater and sludge samples originated from Athens WWTP. PFC concentrations up to 113 ng L⁻¹ (PFUdA), 33 ng L⁻¹ (PFOA) and 1042 ng g⁻¹ (PFUdA) were determined in influent wastewater, treated wastewater and dewatered sludge, respectively. Analysis of PFCs in the particulate matter of wastewater is needed to avoid underestimation of their concentrations.