Comparison of PFAS Recoveries Between WAX/GCB vs. Dispersive GCB SPE Cartridge Formats

Polyfluoroalkyl Substances (PFAS) in the Environment
Poster Presentation

Prepared by R. Jack, S. Lodge
Phenomenex, 411 Madrid Avenue, Torrance, CA, 90501, United States

Contact Information: [email protected]; 408-242-2996


We will demonstrate that Strata PFAS single tube WAX/GCB sample preparation provides LC-MS/MS recovery and precision for non-drinking water PFAS analysis that is equivalent to WAX followed by dispersed GCB, thereby meeting DoD QSM 5.4 and the recent draft EPA 1633 requirements. Extensive LC-MS/MS analysis of drinking water samples has firmly established the efficacy of solid phase extraction with a weak anion exchange (WAX) sorbent to extract, pre-concentrate and purify a wide variety of PFAS compounds prior to analysis. However, the analysis of non-drinking water samples, such as treated wastewater, untreated wastewater, and stormwater runoff, is much more challenging. These more complex matrices can introduce additional chromatographic and spectral interferences which can unacceptably depress or inflate analyte recoveries. QSM 5.4 and EPA 1633 specify a two-step sample preparation step utilizing WAX followed by graphitized carbon black (GCB) for the analysis of all non-drinking water matrices. Initially, laboratories applied the WAX + GCB procedures sequentially by adding finely powdered GCB to the WAX treated eluent, thereby resulting in a dispersion (dGCB). The dGCB must then be removed by centrifugation and filtration and separately eluted to recover the adsorbed PFAS analytes. This time consuming and imprecise procedure was later improved by placing the GCB in a separate SPE tube. This results in a sequential, two-tube procedure (WAX followed by GCB) that is less error prone than WAX followed by dGCB. However, this two-step preparation process is still time consuming and increases laboratory cost through the addition of a second cartridge. A final improvement came when the WAX and GGB were combined in a single tube (Strata PFAS) to offer equivalent analytical performance, but with additional improvements in lower cost and higher laboratory productivity. Furthermore, owing to reduced sample handling, the single tube WAX/GCB sample preparation format reduces sample preparation time, material cost, and labor cost, thereby increasing laboratory productivity and sample throughput as compared to the traditional two-step sample preparation process.