An optimized processing method for polar organic chemical integrative samplers deployed in seawater: Toward a maximization of the analysis accuracy for trace emerging contaminants

Passive sampling of emerging contaminants (ECs) in seawater represents a challenge in environmental monitoring. A specific protocol for Polar Organic Chemical Integrative Sampler (POCIS) processing may be necessary when dealing with marine applications, due to the peculiarity of the considered matrix. Herein, both the instrumental LC-MS/MS analysis and the sampler processing for the determination of 22 ECs in seawater were carefully optimized. The study entailed a test simulating POCIS sorbent expo-sure to seawater as well as the processing of replicated field POCIS with different elution solvents. The final method involved washing the sorbent with water, to eliminate most salts, and a two-step elution, by using methanol and a small volume of a dichloromethane-isopropanol mixture. With this protocol, recoveries between 58 and 137% (average 106%) were obtained for most analytes, including non-steroidal anti-inflammatory drugs, UV-filters, perfluorinated substances and caffeine. Still, the protocol was not suitable for very hydrophilic compounds (recovery under 20% for artificial sweeteners and the pharmaceutical salbutamol), which also showed remarkable ion suppression (matrix effects in the range 4-46%). For all other chemicals, the matrix effects were in the range 67-103% (average 86%), indicating satisfactory ac-curacy. Also, the overall method showed high sensitivity (detection limits in the range 0.04-9 ng g-1 of POCIS sorbent) and excellent specificity, thanks to the monitoring of two "precursor ion-product ion" MS transitions for identity confirmation. The method was applied to samplers deployed in the Ligurian coast (Italy), detecting caffeine, bisphenol A, ketoprofen and two UV-filters as the most concentrated in the POCIS sorbent.