The presence of pharmaceuticals in nature systems poses a threat to the environment, plants, animals, and, last but not least, human health. Their transport in soils, waters, and sediments plays important roles in the toxicity and bioavailability of pharmaceuticals. The mobility of pharmaceuticals can be affected by their interactions with organic matter and other soil and water constituents. In this study, a model agarose hydrogel enriched by humic acid as a representative of organic matter is used as a transport medium for pharmaceuticals. Sulphapyridine (as a representative of sulphonamide antibiotics) and diclofenac (as a representative of widely used non-steroidal anti-inflammatory drugs) were chosen for experiments in diffusion cells. Pharmaceuticals were passed through the hydrogel from the donor solution to the acceptor compartment and could interact with humic acids incorporated in the hydrogel. The lag time was prolonged if the hydrogel was enriched by humic acids from 134 to 390 s for sulphapyridine and from 323 to 606 s for diclofenac. Similarly, the incorporation of humic acids in the hydrogel resulted in a decrease in the determined diffusion coefficients. The decrease was stronger in the first stage of the experiment when diffusing particles could interact with vacant binding sites.

• Keywords
• diclofenac, humic acid, hydrogel, sulphapyridine, transport,
• MeSH
• Diffusion MeSH
• Diclofenac * chemistry   MeSH
• Humic Substances * analysis   MeSH
• Hydrogels * chemistry   MeSH
• Pharmaceutical Preparations chemistry   MeSH
• Sepharose * chemistry   MeSH
• Sulfapyridine chemistry   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Diclofenac * MeSH
• Humic Substances * MeSH
• Hydrogels * MeSH
• Pharmaceutical Preparations MeSH
• Sepharose * MeSH
• Sulfapyridine MeSH

The transport properties of agarose hydrogels enriched by humic acids were studied. Methylene blue, rhodamine 6G and Cu(II) ions were incorporated into hydrogel as diffusion probes, and then their release into water was monitored. Cu(II) ions as well as both the dyes studied in this work have high affinity to humic substances and their interactions strongly affected their diffusion in hydrogels. It was confirmed that humic acids retarded the transport of diffusion probes. Humic acids' enrichment caused the decrease in the values of effective diffusion coefficients due to their complexation with diffusion probes. In general, the diffusion of dyes was more affected by the complexation with humic acids in comparison with Cu(II) ions. The effect of complexation was selective for the particular diffusion probe. The strongest effect was obtained for the diffusion of methylene blue. It was assumed that metal ions interacted preferentially with acidic functional groups. In contrast to Cu(II) ions, dyes can interact with acidic functional groups, and the condensed cyclic structures of the dye probes supported their interactions with the hydrophobic domains of humic substances.

• Keywords
• agarose, diffusion, humic acid, hydrogel, reactivity,
• Publication type
• Journal Article MeSH