Polar Organic Chemical Integrative Samplers (POCIS) with two supporting polyethersulfone (PES) membranes and a strong adsorbent in between are frequently used to determine the concentrations of polar organic contaminants in the aqueous environment. The solute transfer rate (SRs) through PES is a key parameter affecting the critical membrane/water partitioning coefficient (Rmw) of polar organic molecules, which in turn affects the concentration of these molecules on the adsorbent and the accuracy of POCIS measurement. However, information on SRs and Rmw in the literature is very limited. Prolonged use of POCIS in the measurement of organic compounds may lead to membrane fouling by the retained organic compounds. The relationship between the properties of the polar organic compounds and their different accumulation behaviors in POCIS is not yet clear. This study aimed to measuring the solute transfer rate of four polar organic compounds (atrazine, caffeine, ibuprofen, and atenolol). The results indicated that atrazine had the highest SR of 0.49 mL day-1. Both caffeine and atenolol had an SRs of approximately 0.3 mL day-1. Ibuprofen had the lowest SR of 0.23 mL day-1. The results further revealed that the tendency of the organic solutes to adsorb onto interstitial spaces of the PES polymer was associated with their hydrophobicity and molecular structures.
Keywords: Mechanism; PES membrane; Passive sampler; Polar organic compounds; Solute transfer rate.