An Insight into the Use of Polyethersufone Membrane as a Single-Phase Passive Sampler for Emerging Contaminants in Water

The Polar Organic Chemical Integrative Sampler (POCIS) is a passive sampler principally used for the detection of hydrophilic molecules in aqueous matrices. The standard configuration of POCIS consists of a receiving phase sandwiched between two polyethersufone (PES) membranes. Recently, the uptake of several analytes (hydrophilic and hydrophobic) has been assessed both in the sorbent phase and in the PES membranes. Due to its sorption ability, the PES polymer was used as integrative passive sampler for several emerging contaminants (ECs) in hollow fibers or flat sheet membranes configuration. This study focused on the use of the POCIS PES membrane as a passive sampler itself for ten ECs which showed good uptake onto the membrane in a previous study: five UV filters, Bisphenol A, Triclosan and three estrogens. The aim was to assess the sorption kinetics of analytes with different hydrophobicity (LogD at pH = 8 between 2.67 and 6.78), to determine the membrane-water partition coefficients (Kmw) and the sampling rate (Rs), where a linear accumulation trend was observed. Several experiments were conducted by exposing the membranes in beakers containing water spiked with the selected ECs. The first calibration was carried out using the static renewal techniques to evaluate the analytes uptake during 96h of deployment. In a second experiment (8 hours calibration), the impact of different hydrodynamic condition (static vs. agitation) on the sorption kinetics was assessed. Finally, the Kmw were determined using the single dose design. After the exposure experiments, the membranes were eluted with methanol under gentle agitation and analytes detection was carried out using liquid chromatography coupled to tandem mass spectrometry. A test involving a spike directly on the membrane and a subsequent extraction was performed to verify recovery and matrix effect (possibly due to impurities released by the PES material) of the procedure. The data obtained showed a linear uptake during at least 96 hours for six analytes (Type I), while four compounds (Type II) reached the equilibrium in almost 24 hours. Rs were thus determined only for Type I analytes. Concerning the flow sensitivity of the sampler, two behaviors were observed: the more hydrophobic analytes (LogKow > 5) were sensitive to the hydrodynamic changes, while for substances with LogKow < 5 the flow rate had not influence on the uptake during the first 2-4 hours. Finally, thanks to the Kmw values obtained, the capacity of the sampler was estimated. The application of PES membranes in water as kinetic sampler for Type I compounds and as equilibrium sampler for Type II chemicals was demonstrated. Future developments involve the evaluation of the linear uptake regime during longer deployments as well as the application to real samples (deployment of the samplers in surface waters).