PFASs, often referred to as "forever" chemicals, are widespread in various environments, including soils and aquatic systems, due to their extensive use. Surface waters in several European countries, particularly in marinas and ports with heavy boat traffic, need further investigation as potential sources of contamination. Reliable methods for the extraction and quantification of these emerging compounds are crucial. This study aimed to enhance an existing solid-phase extraction method for analyzing surface water from marinas and ports with varying salinities (2, 9, and 17 PSU).

The objectives were to 1) optimise the solid-phase extraction method, considering matrix salinity effects and cross-contamination; 2) validate the extraction and quantification method for 18 EPA 537.1 PFASs in estuarine surface waters, using Ultra-High-Performance Liquid Chromatography–Quadrupole Time–Of–Flight Tandem Mass Spectrometry, and 3) apply the optimised method to PFAS quantification in three Portuguese marinas.

All the ICH criteria were successfully validated at 9 PSU. The limits of quantification ranged from 117.80 ng/L to 385 ng/L, with the exception of that for PFHpA (645.85 ng/L). The PFAS levels (PFOA, HFPO-DA, PFBS, PFHxS, and PFOS) were relatively low, with a maximum of <0.32 ng/L observed only for PFOA. In Freixo Marina, the total average concentrations were slightly higher (∑PFAS= 1.02 ng/L) compared to those found in Cais da Ribeira Port (∑PFAS= 0.94 ng/L) and Afurada Marina (∑PFAS= 0.81 ng/L). The PFOS concentrations were below the limit values set by the Environmental Quality Standards (36000 ng/L of PFOS for inland surface water), similar to findings in other Portuguese river studies. This study facilitated the development of a precise and reliable method for the extraction and quantification of PFASs in estuarine surface waters, particularly from marinas. This method can be readily applied to analyzing PFASs in other estuarine samples.