Accelerated solvent extraction (ASE) to support the implementation of silicone passive sampler-based monitoring of hydrophobic contaminants.

Aquatic silicone passive samplers are increasingly used to measure hydrophobic micropollutant concentrations, such as polychlorobiphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs), because of their high sampling rate. However, extraction is often time- and resource-consuming, usually done by traditional solvent-based techniques followed by column chromatography clean-up. This study assessed the potential of accelerated solvent extraction (ASE) for simultaneous extraction and clean-up of silicone passive samplers for large-scale monitoring of hydrophobic contaminants. Nine ASE methods were tested with hexane and dichloromethane as extraction solvents and silica gel and aluminium oxide as clean-up adsorbents. Recovery rates for the three compound families were 10-20% lower than with Soxhlet extraction followed by column chromatography clean-up. The method using 25 g of adsorbents (1:1, w:w), a 3:1 hexane/dichloromethane solvent ratio and a temperature of 103 °C was chosen for its high recovery rates, low variability and low solvent and adsorbent use. This ASE method halved extraction time compared to Soxhlet extraction and was successfully tested on field-deployed passive samplers with relative recovery rates around 80% compared to Soxhlet, and relative standard deviation (%RSD) around 30%. Its application on the monitoring of 21 sampling sites in the Geneva Lake Basin showed satisfying results, with median relative errors of 11% on sampling rates (and extrapolated water concentration), compared to 7% for the Soxhlet method. The slightly lower concentrations did not impact the detection of pollution problems. The developed ASE method proved to be more efficient than Soxhlet extraction in the monitoring of hydrophobic compounds.