# Water Modification by Cold Plasma Jet with Respect to Physical and Chemical Properties
## 4 Conclusions  
In the present report, buffered or unbuffered water was exposed to the species produced by an atmospheric pressure cold plasma in the form of a plasma jet, operating with argon, driven by audio frequency sinusoidal high voltage, and consuming less than 400 mW mean power. It was shown that radicals are produced in the gaseous phase and their interaction with the liquid targets leads to (i) evaporation, (ii) acidification, (iii) increased oxidizer concentrations, and (iv) increased ionic species, in agreement with previous reports. \({}^{\bullet}\)OH, H\({}_{2}\)O\({}_{2}\), and O\({}_{2}^{\bullet-}\) were specifically identified and quantified by innovative methodologies.  
Analytically, the above-mentioned quantities for 30 min plasma treatment of the unbuffered water were found to be: mass reduction 14.5%, pH decrease 1.98, redox potential increase 60.5 mV, conductivity increase 30.33 \(\upmu\)S cm\({}^{-1}\), \({}^{\bullet}\)OH concentration 550 nM, H\({}_{2}\)O\({}_{2}\) concentration 350 \(\upmu\)M, and O\({}_{2}^{\bullet-}\) concentration 850 nM. The corresponding values for the buffered solution were found to be: 15.6%, 0.18, 10 mV, 3.1 mS cm\({}^{-1}\), 450 nM, 250 \(\upmu\)M, and 80 nM. It was demonstrated that these physicochemical changes take place while both liquids maintain a low temperature. These combined features of the plasma activated water have important implications, both to biomedical and environmental fields.  
**Author Contributions:** P.S.: conceptualization; investigation; methodology; project administration; funding acquisition; supervision; resources; writing--original draft preparation; writing--review and editing; validation. M.P.: investigation; methodology; software; data curation; formal analysis; validation; visualization. K.P.: investigation; methodology; software; data curation; formal analysis; visualization. E.K.: investigation; methodology; data curation; formal analysis. M.S.: investigation; methodology; data curation; formal analysis. P.P.: investigation; methodology; data curation; formal analysis. A.V.: investigation; methodology; data curation; formal analysis. E.G.: conceptualization; supervision; writing--review and editing; validation. C.D.G.: conceptualization; funding acquisition; supervision; resources; writing--original draft preparation; writing--review and editing; validation. S.G.: writing--review and editing; validation. C.K.: writing--review and editing; validation. C.K.: writing--review and editing; validation. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the Greek Ministry of Education. Part of the research conducted and presented in the present study was supported by the Hellenic Foundation for Research and Innovation (HFRI), under the HFRI PhD Fellowship grant (Number 653). Additionally, this work was supported by the \"Andreas Mentzelopoulos Foundation\" (Grant Number 33720000) of the University of Patras.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
**Conflicts of Interest:** The authors declare no conflict of interest.