Experimental Investigation of Plasma Activated Ethanol Water Solution
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Healthcare-associated infections (HAI) are infections that patients acquire while being treated at health care centers. Atmospheric pressure air plasmas created at or near room temperature are promising for treating HAI because of their strong anti-microbial effects, convenience and safety. Instead of applying plasma directly to biological substrates, chemical species from plasma can be used to activate liquids which in turn can be used to inactivate microorganisms. It has been known that plasma activated water (PAW) has strong anti-microbial properties, but recent studies show that plasma activated ethanol water (PAEW) solution has stronger sporicidal effects than PAW and results in 6 log reduction of bacterial endospores. Compared to PAW, little is known about chemical species in PAEW responsible for the sporicidal effects. The current work aims to identify species responsible for the significant sporicidal properties of PAEW compared to PAW. A dielectric barrier discharge setup was used to activate the ethanol water solution with non-thermal ambient air plasma with this application in mind. The resulting plasma activated ethanol water solution is analyzed using various qualitative techniques like mass vs time trials, UV spectroscopy, FTIR spectroscopy and GCMS tests to identify the chemical species formed after plasma treatment. Quantitative analysis using various colorimetric and enzymatic assay tests was performed to quantify the chemical species formed in the ethanol water solution after plasma treatment. The spectroscopic tests revealed the presence of chemical species like nitrites, nitrates and hydrogen peroxide in PAEW similar to that of PAW. New species with strong sporicidal activities like acetic acid and peracetic acid were also found in PAEW. These new species were later corroborated and quantified by well-known colorimetric and enzymatic assay tests specific for each species. The concentrations of acetic acid and peracetic acid were found to be in the 90 to 300 ppm range and 200 ppm range respectively after one minute of plasma treatment. Finally, a possible route for sporicidal action of peracetic acid is also discussed.
Sebastian, Josef (2017). Experimental Investigation of Plasma Activated Ethanol Water Solution. Master's thesis, Texas A & M University. Available electronically from