Calibration of silicone rubber passive samplers: experimental and modeled relations between sampling rate and...

Sampling rates (Rs) for silicone rubber (SR) passive samplers were measured under two different hydrodynamic conditions. Concentrations were maintained in the aqueous phase by continuous equilibration with SR sheets of a large total surface area which had been spiked with polycyclic aromatic hydrocarbons and/or polychlorinated biphenyls. Test sheets made of the same SR but of much smaller surface area were used to measure the uptake rate. Measured Rs values decreased with increasing passive sampler-water partition coefficient (Kpw) according to Rs approximately Kpw(-0.08) under both hydrodynamic conditions. This decrease is not significantly different from modeled values if the uncertainty of the diffusion coefficients in water is included. Modeling also confirmed that uptake of the test compounds under the experimental conditions was entirely controlled by diffusion in the water phase. A model using Rs approximately M(-0.47) is suggested for extrapolation of Rs estimated from the dissipation of performance reference compounds to target compounds in a higher hydrophobicity range.