Effect of feed-gas humidity on nitrogen atmospheric-pressure plasma jet for biological applications

OBJECTIVE: We investigate the effect of feed-gas humidity on the oxidative properties of an atmospheric-pressure plasma jet using nitrogen gas. BACKGROUND: Plasma jets operating at atmospheric pressure are finding uses in medical and biological settings for sterilization and other applications involving oxidative stress applied to organisms. Most jets use noble gases, but some researchers use less expensive nitrogen gas. The feed-gas water content (humidity) has been found to influence the performance of noble-gas plasma jets, but has not yet been systematically investigated for jets using nitrogen gas. METHOD: Low-humidity and high-humidity feed gases were used in a nitrogen plasma jet, and the oxidation effect of the jet was measured quantitatively using a chemical dosimeter known as FBX (ferrous sulfate-benzoic acid-xylenol orange). RESULTS: The plasma jet using high humidity was found to have about ten times the oxidation effect of the low-humidity jet, as measured by comparison with the addition of measured amounts of hydrogen peroxide to the FBX dosimeter. CONCLUSIONS: Atmospheric-pressure plasma jets using nitrogen as a feed gas have a greater oxidizing effect with a high level of humidity added to the feed gas.