Effect of liquid-dissolved gas components on concentrations of the aqueous reactive oxygen and nitrogen species

Abstract

The reactive oxygen and nitrogen species (RONS) conversion process occurring in a liquid environment is a key issue in plasma biomedical applications and clinical treatment processes. The liquid-dissolved gas components could participate in the aqueous RONS forming process, which is very important for better understanding the chemical mechanism of the aqueous RONS formation. In this article, double distilled water (DDW) with five different gas compositions (unprocessed DDW, DDW without air, DDW with O2, DDW with N2, and DDW with CO2) is first used in experiments to help systematically understand the reaction mechanism of the aqueous RONS with different liquid-dissolved gases. It was found that the presence of dissolved O2 favored the formation of hydroxyl, while CO2 was somewhat detrimental to the formation of hydroxyl. Both dissolved O2 and CO2 are beneficial to the formation of hydrogen peroxide and nitrite, but the effect of CO2 is slightly stronger. Also, they both have a similar effect on the formation of nitrate. Nitrogen has a certain promoting effect on the formation of hydroxyl, nitrite, and nitrate. In summary, the liquid-dissolved gas contents play important roles in the formation of the aqueous RONS.