The Rapid Decrease in the Biological Reactivity of Water Activated by Air Spark Discharge Plasma

To investigate the biological reactivity of plasma-activated water (PAW), we prepared PAW using atmospheric air spark discharge over water at 4°C and 25°C, with Escherichia Coli ( E. coli ) as the microbial model. The biological reactivity of PAW at 25°C decreased rapidly by 3.32 Logs within 20 s of storage. At 4°C, PAW showed high reactivity within 20–30 s of storage but decreased by 3.50 Logs between 30 and 60 s. Our analysis revealed that PAW reactivity is dependent on short-lived peroxynitrite (ONOOH), formed through H 2 O 2 and HNO 2 under acidic conditions. ONOOH actively reacts with amino acid functional groups, as measured by high-resolution LC-MS, likely contributing to the rapid inactivation of E. coli .