Production, shelf life and surface sanitizing efficacy of plasma-treated liquids

In recent years, the importance of plasma-activated water (PAW) and plasma-treated liquids (PTL) as an alternative to conventional sanitization and disinfection methods has steadily increased, as they offer several advantages over conventional methods. We have therefore produced PTL using a dielectric barrier discharge plasma jet and an arc discharge plasma system and investigated the suitability as surface disinfectants. The formation and durability of the reactive species in the PTL were investigated indirectly via the pH value, the electrical conductivity and the oxidation-reduction potential as well as directly by measuring the concentration of dissolved ozone. Additionally, microbiological tests were carried out to evaluate the antibacterial efficacy of PTL against Escherichia coli, inoculated on varying material types. In our studies on the production of PTL, we were able to identify differences between the plasma discharge types and the resulting characteristics of the PTL. Storage studies on PTL showed that the shelf life increases with increasing plasma treatment time and lasts for over 300 days. The antibacterial efficacy depended on the volume of PTL used, the incubation time, the substrate material inoculated with bacteria and the plasma source used to produce PTL. Depending on the parameters, a bacterial inactivation of up to 4 log was demonstrated. We were thus able to show that PTLs have the potential to be used as surface disinfectants.