Sterilization characteristics inside narrow tube using nitrogen oxides generated by atmospheric pressure air plasma

Abstract

Abstract The sterilization characteristics of the inner surface of silicon tube were investigated using active species generated by atmospheric dielectric barrier discharge (DBD) plasma using air and oxygen gas. A DBD torch-type device installed at one end of the tube and generated long-lifetime active species flowing into the tube. The strip-type BI (Biological indicator) with 105 spore-forming bacteria placed at the position opposite to the DBD device in a 60 cm tube was sterilized within 30 min by active particles generated from air plasma. Major factors for the sterilization using air plasma were HNO3 and N2O5. When the organic materials (keratin, aspartic acid and dipicolinic acid) comprising spores were treated same as sterilization, the treatment hardly changed the composition of dipicolinic acid. Keratin was oxidized by ozone and NOx generated from oxygen plasma and air plasma. The result of aspartic acid showed little change in composition by ozone generated from oxygen plasma, whereas nitro (NO2), nitroso (NO) and aldehyde (CHO) groups were formed by ozone and NOx generated from air plasma.