Comparison of different triolein-based composite semipermeable membranes for passive sampling of organochlorine pesticides

Passive sampling methods have been widely used for more than 20 years because they can provide information on time-weighted average concentrations (C _TWA) of hydrophobic organic contaminants in water. Many factors affect the efficiency and applicability of a passive sampling process. Among others, selection of the sampler design and choice of the supporting membrane material are important factors that determine the performance of passive samplers. In this work, the influences of some critical properties of membranes, such as membrane density, hydrophilicity of the membrane surface, and chemical and mechanical resistances, on the uptake of organic chlorinated pesticides (OCPs) were evaluated. Four membrane materials, namely cellulose acetate (CA), cellulose acetate butyrate (CAB), a cellulose acetate-cellulose triacetate blend (CA-CTA), and cellulose triacetate (CTA), and their triolein-embedded samplers were selected for the study. The four membranes are all hydrophilic; CAB has the highest contact angle and CA has the lowest. CTA is chemically and mechanically resistant, and has better tensile strength than the other membranes have. CAB does not have good chemical resistance and dissolves in hexane/dichloromethane solvent. CA and CTA alone showed lower uptake rates for the selected OCPs than with triolein-embedded passive samplers, indicating that triolein increased the accumulation capacity. Triolein-embedded CA (TECAM), CA-CTA (TECA-CTA), CTA (TECTA), and CAB (TECAB) as passive samplers showed similar uptake patterns; TECTA showed the highest uptake rates and TECAB showed the poorest accumulation. In summary, TECTA gave the best performance among all the tested composite semipermeable membranes.