Optimisation, calibration and field testing of passive sampling devices for monitoring of polar
organic compounds

Jakub Urík

Masaryk University, Research Centre for Toxic Compounds in the Environment (RECETOX), Kamenice
753/5, 625 00 Brno, Czech Republic

The concept of passive sampling, where sampler accumulates compounds from sampled medium passively
via diffusion, has been extensively developing over last decades and is nowadays commonly used in
monitoring of trace contaminants in the environment. However, passive samplers for polar compounds
in water pose a challenge, as their use is limited due to effect of hydrodynamic conditions,
especially water flow rate, on uptake of compounds. Hydrogel-based samplers were recently
introduced as a possible solution to the issue. The samplers contain thick diffusive layer of
hydrogel with properties similar to stationary water, thus minimising the effect of water flow rate
on sampling.

Suitability of 1.5% agarose hydrogel as a diffusive medium for diverse group of emerging polar
contaminants (currently used pesticides, pharmaceuticals, personal care products and perfluorinated
compounds) was tested. For most compounds, no sorption to pure hydrogel was found. Diffusion
coefficients in hydrogel were measured at different temperatures, which allows the prediction of
sampling rates even without further calibration. Diffusion coefficients of few selected compounds
were also measured in water with comparable results. 1.5% agarose hydrogel thus proved suitable for
use in a passive sampler.

Agarose hydrogel sampler based on diffusion gradient in thin films (DGT) with Oasis HLB sorbent and
sampling area of 3.1 cm^2 was calibrated in laboratory conditions. The overall sampling rate was
too low, reaching values down to 1.1 mL/day. Therefore, a novel sampler design was proposed, with
the sampling area of 22.7 cm^2. This design was tested on several field locations and compared with
other passive samplers, spot samples and composite samples. Findings prove that the novel agarose
hydrogel‑based passive sampler can be reliably used for monitoring of spatial trends of water
contamination by trace pollutants and determining time-weighted average water concentration values
below ng/L.