Cleanup of Per- and Polyfluoroalkyl Substances in Solid Samples Using EPA Method 1633 with a Vacuum-based Automated Solid Phase Extraction System

Per- and Polyfluoroalkyl Substances (PFAS) in the Environment
Poster Presentation

Prepared by T. Hall, R. Addink
Fluid Management Systems, 900 Technology Park Drive, Billerica, Massachusetts, MA 01821, United States


Contact Information: [email protected]; 617-393-2396

ABSTRACT

USEPA 1633 is the most comprehensive PFAS method with analysis of forty native PFAS and twenty-four labeled surrogates. The method comprises a wide variety of matrices, including biosolids, fish tissue, ground water, landfill leachate, soil, surface water, and wastewater.

Extraction of solids in methanol for PFAS analysis followed by sample concentration, exchange into water, Solid Phase Extraction, and cleanup - one of the key processes described in the method - has prompted attempts to automate this last step. The method describes cleanup steps using loose carbon or cartridges containing carbon.

An automated vacuum-based system was designed with a minimum number of valves and a short and simple pathway from extract to cartridge. Although the system initially was meant for use with wastewater samples containing particulate, it can also be employed for cleanup over graphitized carbon black contained in a WAX (Weak Anion Exchange) cartridge.

The chemicals used in the process were 1% methanolic ammonium hydroxide, formic acid in water, reagent water, and formic acid in methanol. Sample loading was facilitated by a vacuum pump, while conditioning and elution were conducted using positive pressure. Cartridge drying was achieved with vacuum/nitrogen. Bottle rinses were done using nitrogen to spray the bottle. The resulting extracts were collected in polypropylene tubes without any further concentration. Additionally, relevant recovery standards were added before the LC/MS analysis.

Soil samples were manually extracted in 0.3% ammonium hydroxide/methanol, concentrated to a few mLs of methanol, diluted with water to 50 mLs and then underwent Solid Phase Extraction and cleanup as per the method described above. Labeled recoveries of the 24 surrogates were > 70%.

The results show the automated system can be effectively used for the cleanup part of PFAS analysis in solids with particularly good recoveries. Mixed WAX/graphitized carbon black cartridges perform excellent cleanup.