Electrochemical removal of antiretroviral drug - raltegravir from aquatic media: Multivariate optimization, degradation studies and transformation products characterization

Electrochemical degradation of the antiretroviral drug raltegravir was investigated using different electrode materials (platinum, glassy carbon and boron-doped diamond). After preliminary studies with the use of multivariate chemometric method, electrochemical degradation was conducted with a boron-doped diamond electrode and phosphate buffer at pH 9. To assess the role of different variable in degradation kinetics, final experiments were conducted with varying applied current densities, chloride and humic acid concentrations, and using a natural river water sample. The results showed that raltegravir degradation generally followed pseudo-first-order kinetics. The degradation rate was inhibited by the presence of humic acid, while increasing the applied current density or chloride concentration enhanced the removal of raltegravir. Degradation process performed in the river water sample followed second-order kinetics and led to almost complete degradation of raltegravir within 30 min, highlighting the impact of natural matrices on reaction kinetics. Total organic carbon analysis was utilized, showing that even rapid degradation of the parent compound did not ensure total mineralization. Additionally, the energy consumption analysis revealed that the presence of chloride ions significantly improves efficiency of the organic carbon elimination. With the use of high-resolution mass spectrometry fourteen transformation products were elucidated, and their aquatic toxicity was predicted using in silico approach. Half of the identified transformation products were found to possess higher aquatic toxic potential than the parent compound, emphasizing the necessity of the mineralization assessment.