Simplifying EPA 1633 Analyses with an Improved Dual-Bed Solid-Phase Extraction Method

Abstract: Solid-phase extraction (SPE) is a valuable sample preparation technique for environmental matrices utilized in extracting pesticides, semivolatiles, and emerging contaminants from water samples. Despite its efficacy, SPE encounters challenges in non-potable water matrices where traditional ion-exchange SPE fails to remove certain matrix interferences, leading to the implementation of dispersive carbon protocols. Furthermore, solid particles in the sample can obstruct SPE cartridges, prolonging extraction or needing multiple cartridges to complete the analysis. The recent EPA Method 1633 aims at the analyses of PFAS in aqueous, solids, biosolids, and tissue samples where extract cleanup steps, as well as percent solids, can affect the overall length and performance of the sample preparation. In this work, WAX and Graphitized Carbon Black (GCB) dual-bed SPE cartridges were compared to conventional single-bed SPE formats towards precision, accuracy, and reduction of semi and nonvolatile residues. Furthermore, a novel filter aid was assessed for the mitigation of cartridge clogging and compared to glass wool using an ASTM substitute wastewater matrix. The recoveries for all 40 PFAS analytes in the fortified sample ranged from 80%-120%, and the relative standard deviation was less than 20% for most of the analytes. The advantage of the filter aid was significant as it provided 60% better filtration efficiency when compared to glass wool and over 90% when compared to the unfiltered SPE controls. The experimental SPE format offered a simplified and consistent approach when dealing with dirty matrices while meeting the accuracy and precision of EPA 1633. Details on the HPLC parameters afforded will also be discussed.