Figure 6. Increasing the He flow decreases the concentration of plasma-induced H₂O₂, NO₂⁻ and NO₃⁻.

500 μl of PBS(Ca²⁺/Mg²⁺) per well in 12 well plate were exposed to 50 or 400 sccm of He plasma for 1, 2 and 4 min. The concentration of H₂O₂ (A) and NO₂/NO₃ (B) were determined using the Na₃VO₄-based method and the nitrate/nitrite colorimetric assay kit, respectively. The data are the mean ± SD of 5 (H₂O₂) and 4 (NO₃⁻ and NO₂⁻) independent experiments. (C) Absorption spectra of a mixture of 300 μM H₂O₂, 500 μM NO₂⁻ and 150 μM NO₃⁻ prepared in PBS(Ca²⁺/Mg²⁺). The data are the mean ± SD of 4 independent experiments. (D) 500 μl of PBS(Ca²⁺/Mg²⁺) were exposed to He plasma at a flow rate of 400 sccm for 2 min, and the absorption spectra were recorded between 200 and 300 nm. The data are the mean ± SD of 3 independent experiments. (E) Comparison between the absorption spectra of a mixture of 300 μM H₂O₂, 500 μM NO₂⁻ and 150 μM NO₃⁻ (curves shown in panel C) and the absorption spectra of plasma-activated PBS(Ca²⁺/Mg²⁺) (curves shown in panel D). As indicated in the panels C, D, and E, the solutions containing H₂O₂, NO₂⁻ and NO₃⁻ or plasma-activated PBS(Ca²⁺/Mg²⁺) were diluted 2x, 4x, or 8x in PBS(Ca²⁺/Mg²⁺) before the spectroscopic measurements.