Effect of salinity and pH on the calibration of the extraction of pharmaceuticals from water by PASSIL.

High salinity and a relatively high pH are two factors characterizing the marine water environment, which is one of the main final reservoirs receiving pharmaceutical residues. The same factors have an undeniable impact on the extraction efficiency and kinetics of uptakes of polar analytes from water by sorbent-based passive sampling techniques. Recently, we presented a novel passive sampling technique, in which ionic liquids are applied as receiving phases for pharmaceutical monitoring in water (the Passive Sampling with Ionic Liquids technique). In this paper we test the impact of salinity and pH on the PASSIL calibration (sampling rate determination) and the extraction efficiencies of sulfonamides, beta-blockers and nonsteroidal anti-inflammatory drugs selected as model contaminants. Trihexyl(tetradecyl)phosphonium dicyanamide ([P666-14][N(CN)2]) was taken as the stable liquid receiving phase. It selectively extracted neutral and negatively charged analytes from donor solutions of different pH (1, 3, 7 and 9). The presence of salt (7, 20 and 35 PSU) decreased the efficiency (by 5-65%) and Rs (by 0.017Lday-1 to 0.574Lday-1) of PASSIL for all target compounds. The general conclusion is that salinity and pH have a significant impact on the calibration of passive dosimeters for ionizable compounds, both for the new PASSIL technique and standard POCIS techniques.