Radiation induced degradation of antiepileptic drug primidone in aqueous solution

• Electron beam irradiation was efficient for removal of primidone in aqueous solution.
• The degradation kinetics of primidone conformed to pseudo-first-order equation.
• Hydroxyl radical was shown to be the most reactive species in primidone radiolysis.
• Possible pathways of primidone degradation were proposed.

The present study was to determine the effectiveness of electron beam irradiation for degradation of the antiepileptic drug primidone (PMD) in aqueous solution. The results showed that PMD degradation followed pseudo-first-order kinetics. The dose constant determined in this study ranged from 1.26 to 4.59 kGy−1, and decreased with an increase in the PMD initial concentration, whereas the initial radiation chemical yield for the loss of PMD decreased with increasing of absorbed dose and increased as the PMD concentration increased. The effects of medium pH, the presence of SO42−, SO32−, CO32−, HCO3−, NO3− and NO2− anions, H2O2, iso-propanol, and saturated solutions of N2, O2, N2O were also investigated. The results demonstrated that the OH took the most important role in the degradation of PMD, while the reductive eaq− and H took the less important role in PMD degradation. Major degradation products of PMD, including degradation intermediates, low weight organic acids and some inorganic ions were detected by LC/MS/MS and IC. Formic acid, acetic acid, oxalic acid, maleic acid and NO3−, NH4+ were identified in the irradiated solutions. Possible pathways for PMD decomposition by electron beam irradiation in aqueous solution were proposed.