Direct Injection Method for LC-MS/MS Detection of Polyfluoroalkyl Substances in Water

Oral Presentation

Prepared by D. Stevens, K. Organitini
Waters Corporation, 34 Maple Street, Milford, MA, 01757, United States


Contact Information: doug_stevens@waters.com; 508-482-4672


ABSTRACT

Polyfluoroalkyl substances (PFASs) are common, man-made, persistent environmental contaminants that are used in the production of many consumer products. Common uses of PFASs in consumer goods are as non-stick coatings and for stain or water resistance. Widespread use of these compounds has led to their release into the environment, making them an important class of compounds for monitoring programs globally. Two of the most common PFASs, PFOS and PFOA, were included in the US EPA Third Unregulated Contaminant Monitoring Rule (UCMR 3) occurrence study and showed significant detection levels and occurrence frequency for water sources across the USA. These findings, combined with human health impact studies, have resulted in EPA establishing a drinking water health advisory level of 70ppt.
Currently, there are two main LC/MS/MS approaches used for the analysis of PFASs in water. The first involves SPE enrichment of drinking water samples as in EPA Method 537. The second uses direct injection of water samples. The focus of this presentation will be on the latter type of analysis utilizing direct injection of diluted water in accordance with ASTM 7979. Various sources of non-drinking water (i.e. influent, effluent, river water) were evaluated. Sample preparation consists of a dilution of the sample with methanol followed by syringe filtration. A volume of 50 ul was injected on a highly sensitive LC-MS/MS system equipped with PEEK tubing and an isolator column to remove PFAS contamination from the LC system. ASTM 7979 currently covers 21 PFAS compounds. The method used for this analysis extended the list of PFASs to 40 in order to include some emerging PFAS compounds. Isotopically labeled standards were used to evaluate recovery. Method detection limits for a majority of the compounds tested were at the single parts per trillion (ng/L) level.