Determination of ten perfluorinated compounds in sludge amended soil by ultrasonic extraction and liquid chromatography-tandem mass spectrometry

Abstract

Sludge generated at wastewater treatment plants is normally applied to fields as soil amendment. Nevertheless, sludge may contain perfluorinated compounds that would also be added to soil in this way and then found in soil at different levels. To study the persistence and distribution of perfluorinated compounds in soil after amendment with sludge, a rapid and sensitive method for the analysis of these compounds is needed. An analytical method for the analysis of 10 perfluorinated compounds (five perfluoroalkyl carboxylates, three perfluoroalkyl sulfonates and two perfluoroalkyl sulfonamides) has been developed and validated in this work, using ultrasound assisted extraction followed by a dispersive solid phase extraction (DSPE) clean-up and analysis by LC-MS/MS. The proposed method uses very low volumes of organic solvent per sample, 2.5 mL in the sample preparation procedure and less than 5 mL in the LC analysis, employing a short time for the total performance. Recoveries range from 70 to 105% with good precision, and detection limits are lower than 0.1 ng g⁻¹. The developed method was successfully applied to the determination of perfluorinated compounds in soil and sludge amended soil at different times after sludge application. Low levels of these compounds, in the range of 0.13 to 18.3 ng g⁻¹, were found in the studied samples.