Physicochemical properties and antimicrobial efficacy of argon cold atmospheric pressure plasma jet activated liquids – a comparative study

• Gas-phase and liquid-phase reactive species influences physicochemical and antimicrobial properties of CAPJALs. • Variation in physicochemical properties of CAPJALs dependent on its inherent property. • CAPJALs' bacterial inactivation efficacy follow the trend – DI-W ≈ NS > DW > TW for isolates. • pH and reactive species would play a combined role in bacterial inactivation by CAPJALs. Cold atmospheric pressure plasma jet activated liquids (CAPJALs) have attracted considerable scientific attention due to their peculiar antimicrobial characteristics. In the current context, there is a need to compare the bactericidal activity of CAPJALs and demonstrate the specific parameters necessary to obtain greater effectiveness. This in-vitro research examines the antimicrobial activity of liquids, such as deionized water (DI-W), drinking water (DW), tap water (TW), and normal saline (NS) activated by Ar cold atmospheric pressure plasma jet (CAPJ) against multidrug-resistant (MDR) E. coli and S. aureus . The computed D- value showed that CAPJALs' bacterial inactivation efficacy followed the trend – DI-W ≈ NS > DW > TW for both the isolates. To obtain greater bactericidal effectiveness, an optimum combination of liquid activation time by CAPJ and CAPJAL – bacteria interaction time was noticed. In addition, the rate at which the physicochemical parameters (pH, electrical conductivity (EC), total dissolved solids (TDS), and concentration of reactive species (H 2 O 2 , NO 3 - , and NO 2 - )) changed within the liquid varied in different ways. It was observed that the identified gas-phase species (Ar I, Ar + , N 2 , N 2 + , O I, OH•, OH + , NO + , O 2 + , N 2 O 3 - , NO 3 - , N 2 O 2 - , etc.) would contribute to modification of liquid physicochemical property by generating liquid phase reactive species (NO 3 - , NO 2 - , H + , H 2 O 2 , ONOOH, Cl 2 , HOCl, etc.) via reaction cascades. These reactive species in the liquid phase, together with other physicochemical characteristics, were found to play a part in the process of bacterial inactivation. This study into the underlying mechanism of CAPJ – liquid and CAPJAL – bacteria interaction would help to determine its potential use as a disinfectant in healthcare settings. E. coli: Escherichia coli; S. aureus: Staphylococcus aureus