Desorption of pharmaceutical hydrochlorides from transition metal oxide nanoparticles – investigation by capillary electrophoresis

Abstract

The binding affinity of pharmaceutical hydrochlorides onto transition metal oxide nanoparticles (TMONPs) was investigated through a consecutive process of adsorption and desorption. Mexiletine (MEX) was chosen as a model pharmaceutical hydrochloride that bound onto TMONPs' surface through electrostatic interactions and coordination bonding. Response surface methodology was applied for their optimal separation by capillary electrophoresis to achieve accurate quantitation. Linear and quadratic regressions were applied to model peak resolution and migration times. The response surface methodology was next applied to investigate the maximum desorption percentages of mexiletine (MEX) from the surface of TiO₂ and Co₃O₄ nanoparticles. ANOVA indicated a positive correlation between the MEX desorption results with pH, metformin (MET) competitive desorption agent concentration, Na₂HPO₄ concentration (hence ionic strength), and Na₂S₂O₅ reducing agent concentration. The MEX desorption increased from TiO₂ (46 ± 1%) to Co₃O₄ (63 ± 1%), suggesting a stronger binding interaction between MEX and TiO₂ nanoparticles. TiO₂ exhibited the order of pH > [MET] > [Na₂HPO₄] > [Na₂S₂O₅]; Co₃O₄ exhibited the order [Na₂HPO₄] > pH > [MET] > [Na₂S₂O₅]. This novel finding demonstrates the potential of TMONPs for use as efficient adsorbents to remove pharmaceutical compounds that accidently enter environmental water sources, with feasible regeneration.