Thesis subject

MSc - Speciation of diclofenac in aqueous nanoparticle dispersions

Pharmaceuticals and their metabolites are common contaminants occurring in the aquatic environment. Their concentrations are typically highest in wastewaters but can also be relevant in surface waters, where they may give rise to toxic effects on living organisms.

In the environment, pharmaceuticals generally occur in combination with compounds like their own metabolites, and as associates with other pollutants such as heavy metals, industrial chemicals, pesticides and recently with nanoparticles. Possible mixture effects are therefore relevant and triggered an environmental risk assessment for those kind of complexes, and this forms the motivation for the present project. The idea is to sort out the dynamic speciation of pharmaceuticals (i.e. the different forms in which they occur and the transition between those forms) in aqueous medium containing silica nanoparticles to which they may adsorb. The results in terms of reactivity of the various species will be translated into the corresponding predictions of their bioavailability in aquatic ecosystems.

The project is aiming on explaining the relationships between the different physicochemical forms of the compound – diclofenac, and their ensuing reactivities, mobilities and bioavailabilities in the environment. The laboratory of Physical Chemistry and Colloid Science has been studying the speciation dynamics of metals and organic compounds for several years. While the theoretical concepts for dynamic speciation analysis of metals in colloidal dispersions are well developed, there are still a lot of questions on the behaviour of organic compounds and their nanoparticulate species.

Solid-phase microextraction (SPME) will be applied to characterize the dynamic speciation of a well-known anti-inflammatory drug – diclofenac in a dispersion of silica nanoparticles. The amount of organic pollutant that accumulates into an SPME device with a given hydrophobicity will be correlated with its bioavailable concentration. This will allow determination of the lability characteristics of the nanoparticle-bound species as derived from the dynamics of the process of sorption/desorption by the nanoparticles.

Supervisor: Katarzyna Zielinska

Techniques may include several of the following themes:

Theoretical framework:

  • Dynamic speciation in homogeneous solutions.
  • Dynamic speciation in colloidal ligand systems.
  • Adsorption/desorption kinetics of nanoparticulate-bound pharmaceutical.
  • Lability of bound pharmaceuticals.
  • Extraction kinetics.

Experimental techniques:

  • Solid phase microextraction (SPME)
  • Dynamic light scattering (DLS).
  • High-performance liquid chromatography (HPLC).