Calibration comparison between two passive samplers -o-DGT and POCIS- for 109 hydrophilic emerging and priority organic compounds

The Polar Organic Chemical Integrative Samplers (POCIS) is the most widely used passive sampler for hydrophilic compounds, but unsuitable for certain ionic organic contaminants. The Diffusive Gradient in Thin-Film technique (o-DGT) has shown positive results for both ionic and hydrophilic compounds. However, a calibration step is now needed to evaluate kinetic constant of accumulation for a wide range of molecules.In this study, o-DGT and POCIS were compared for the sampling of three families of micropollutants of potential risk to aquatic environments: 53 pesticides, 36 pharmaceuticals and 20 hormones. A calibration experiment was conducted to compare the kinetic models and constants from a scientific and practical perspective. The results are discussed in a sin-gle table that summarizes the performance of both passive samplers for the 109 compounds of interest. The advantage of o-DGT is that it allows linear accumulation for 72 compounds versus only 33 with POCIS. The mean times to equi-librium obtained with o-DGT are higher than those obtained with POCIS. These results confirm that the presence of a diffusion gel delays the achievement of equilibrium during compound accumulation. Therefore, o-DGT can be consid-ered for situations where POCIS cannot be used due to non-linear accumulation over a typical 14-day deployment pe-riod. However, overall sampling rates and mass transfer coefficients also appear reduced with o-DGT, which is explained by the smaller exchange surface area, as well as the consideration of an additional diffusive layer in this de-vice. This paper also showed that the most appropriate membrane to sample polar compounds with o-DGT was a pol-yethersulfone polymer with a pore size of 5 mu m.

Automated summary

The performance of POCIS and o-DGT as passive samplers for micro pollutants was compared. It was found that o-DGT can be used in situations where POCIS is not suitable, but overall sampling rates and mass transfer coefficients are lower.