Impact of Exposure Time on RONS Concentration Measurements in Plasma-Water Interaction

The interaction between plasma and water is necessary for medical applications. Dielectric barrier discharge (DBD) plasma jets, specifically, are known for their non-equilibrium conditions, which allow for their use to streamline wound healing and sterilization processes. Previous research indicates that plasma-water interactions at wound sites generate reactive oxygen and nitrogen species (RONS), which accelerate the wound healing process. Specifically, nitrite $\left( {{\text{N}}{{\text{O}}_{\text{2}}}^ - } \right)$ and nitrate $\left( {{\text{N}}{{\text{O}}_3}^ - } \right)$ play an important role in vascular homeostasis and antimicrobial action while hydrogen peroxide (H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>) signals mechanisms needed for wound healing. However, measuring the concentration of these RONS is crucial as excessive or insufficient amounts are linked to chronic inflammation, hypoxia, and more negative reactions. A nitrogen plasma jet was utilized to treat water to produce the target RONS (${\text{N}}{{\text{O}}_{\text{2}}}^ - $,${\text{N}}{{\text{O}}_{\text{3}}}^ - $, and H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>). To quantify concentration amounts for each molecule, reference curves were established using standard solutions, and calibration curves were created through an experimental curve fitting routine. The effect of plasma treatment distance was measured through changes in the concentration of RONS, and this paper demonstrates the relationship between these two variables. It was concluded using this experimental methodology to calculate RONS concentration that there is a positive trend that ${\text{N}}{{\text{O}}_{\text{3}}}^ - $ follows with the increase in exposure time. However, H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and ${\text{N}}{{\text{O}}_{\text{2}}}^ - $ both show an increase in concentration as exposure time either increases or decreases away from 10 minutes.