Implementation of an easy and cost-effective method for POCIS in situ calibration using o-DGT for pharmaceutical...

To address the lack of representativeness of sampling rate (R_s) for Polar Organic Chemical Integrative Sampler (POCIS) for water quality study using passive sampling, a novel approach was explored involving Diffusive Gradients in Thin film for organic compounds (o-DGT) as a calibration tool to determine site-specific R_s. In contrast to POCIS, effects of the diffusive boundary layer on water concentration (C_w) determination can be considered for o-DGT. In this approach, o-DGT and POCIS, with similar Oasis® HLB binding phases and polyether sulfone membranes, were exposed under identical conditions. The underlying hypothesis is that both devices will yield the same C_w. Based on this, R_s can be calculated from the masses accumulated by the two devices and the o-DGT calibration parameters. In controlled lab conditions, this study demonstrated the consistency of R_s determined by o-DGT with conventional experimental methods across various hydrodynamic conditions. During field deployments, the limitations of R_s determined by the usual methods were highlighted: C_w sometimes too low for quantification by grab sampling, high uncertainty and strong desorption of Performance Reference Compound (PRC) due to the hydrodynamic conditions. Conversely, the R_s obtained by o-DGT were systematically determined and within the same magnitude as those determined by other available methods. The advantages of this method lie in the readily available o-DGT parameters for each deployment condition and in the measurement of C_w which can be challenging. This calibration method allows to determine site-specific R_s easily and at a low cost. In the context of monitoring programs, deploying o-DGT during initial campaigns could facilitate R_s determination under specific environmental conditions, which can then be applied to subsequent campaigns. Nevertheless, for compounds with low affinity for o-DGT, as Paroxetine, the proposed method is limited to obtain robust R_s.