from the conferences organized by TANGER Ltd.
Transport and reactivity mapping of pharmaceuticals in soil and aquatic environments is vitally important for environmental safety. Pharmaceuticals can interact with organic matter which can result in their partial immobilization and suppression of their migration, bioavailability, and toxicity. Humic substances as important constituents of natural organic matter play important role in this self-healing ability of soils. In this work, they were used for the preparation of hydrogel medium for the monitoring of drug transport accompanied by the interactions between humic substances and drug. Humic hydrogel can be considered as a model system of soil with characteristic content of organic matter. Diclofenac was chosen for the investigation of their transport in hydrogels as a representative of widely used non-steroidal anti-inflammatory drugs. The method of instantaneous planar source was used for the transport and reactivity mapping of diclofenac in humic hydrogel. The method is based on a small defined amount of diffusing substance placed on the circular surface of cylinder-shaped hydrogel (placed in glass tube to achieve one-dimensional diffusion). The method can provide diffusion parameters as effective diffusion coefficients characterizing drug transport affected by interactions with active sites of humic substances and apparent equilibrium constant between immobilized and free movable drug particles. The difference between values based on slope and intercept of linearized mathematical model indicated relatively strong interactions between humic substances as active constituents of hydrogel and diclofenac. The interactions were confirmed by results of adsorption/desorption experiments when around 50 % of diclofenac was not leachable and remained in immobilized form.
Keywords: Diffusion, immobilization, humic substances, hydrogel, diclofenac, adsorption, desorption© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.