Speciation Analysis of Aqueous Nanoparticulate Diclofenac Complexes by Solid-Phase Microextraction

• Published in: Langmuir Vol. 28; no. 41; pp. 14672 - 14680
• Main Authors: Zielińska, Katarzyna, van Leeuwen, Herman P, Thibault, Sylvain, Town, Raewyn M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 16.10.2012
• Subjects: adsorption; Animals; antiinflammatory drugs; aquatic environment; bovine serum albumin; capillary-electrophoresis; Cattle; Chemistry; Colloidal state and disperse state; desorption; diclofenac; Diclofenac - chemistry; dispersions; drug binding-sites; Exact sciences and technology; General and physical chemistry; mass-spectrometry; metal-complexes; nanoparticles; Nanoparticles - chemistry; nd-spme; Physical and chemical studies. Granulometry. Electrokinetic phenomena; prediction; Serum Albumin, Bovine - chemistry; silica; Silicon Dioxide - chemistry; Solid Phase Microextraction; Surface physical chemistry; Thermodynamics; walled carbon nanotubes; Water - chemistry; water samples; Water; Binary compound; Nanoparticle; Silica; Solid; Thermodynamics; Dynamics; Rate constant; Diffusion; Ungulata; Organic compounds; Partition; Bovine; Prediction; Desorption; Serum albumin; Equilibrium; Dispersion; Sorption; Vertebrata; Mammalia; Adsorption; Silicon oxides; Affinity; Artiodactyla; Solid phase; Interface
• ISSN: 0743-7463; 1520-5827; 1520-5827
• DOI: 10.1021/la303143w

The dynamic sorption of an organic compound by nanoparticles (NPs) is analyzed by solid-phase microextraction (SPME) for the example case of the pharmaceutical diclofenac in dispersions of impermeable (silica, SiO2) and permeable (bovine serum albumin, BSA) NPs. It is shown that only the protonated neutral form of diclofenac is accumulated in the solid phase, and hence this species governs the eventual partition equilibrium. On the other hand, the rate of the solid/water partition equilibration is enhanced in the presence of the sorbing nanoparticles of SiO2 and BSA. This feature demonstrates that the NPs themselves do not enter the solid phase to any appreciable extent. The enhanced rate of attainment of equilibrium is due to a shuttle-type of contribution from the NP-species to the diffusive supply of diclofenac to the water/solid interface. For both types of nanoparticulate complexes, the rate constant for desorption (k des) of bound diclofenac was derived from the measured thermodynamic affinity constant and a diffusion-limited rate of adsorption. The computed k des values were found to be sufficiently high to render the NP-bound species labile on the effective time scale of SPME. In agreement with theoretical prediction, the experimental results are quantitatively described by fully labile behavior of the diclofenac/nanoparticle system and an ensuing accumulation rate controlled by the coupled diffusion of neutral, deprotonated, and NP-bound diclofenac species.