How septum materials affect H2O2 accumulation under gamma-irradiation of water in sealed vials: A comparative study on polysiloxane rubber, PTFE, and aluminium

Journal article, 2026

This study investigates the influence of septum materials on the radiolytic generation and steady-state concentration of hydrogen peroxide (H2O2) in deionized water produced through γ-irradiation with a Co-60 source at a dose rate of 3 kGy/h. The experimental findings reveal that polysiloxane rubber septa significantly reduce the steady-state concentration of H2O2 by up to 90 % compared to polytetrafluoroethylene (PTFE) and aluminium septa when in contact with the headspace above the solution. The suppression of H2O2 accumulation was observed exclusively during irradiation. This indicates a radiation-mediated interaction between the silicone rubber and the air-saturated, closed system of the irradiated vials. A plausible explanation is that the O2 in the headspace reacts with Si- and C-centered radicals formed upon irradiation of the silicone. The consumption of the O2 from the head space will lead to the depletion of O2 in the solution as the equilibrium between the gas phase and the liquid must be maintained. This, in turn, explains the lower H2O2 concentrations in the liquid phase since O2 is a precursor for H2O2. These results have implications for the design of experimental setups and the choice of materials in systems where radiolytic processes are significant.