Examination of UV-absorption spectroscopy for analysis of O <sub>3</sub> , NO <sub>2</sub> <sup>−</sup> , and HNO <sub>2</sub> compositions and kinetics in plasma-activated water
Kunihide Tachibana, Toshihiro Nakamura
Abstract
Abstract To examine UV-absorption spectroscopy as a tool for the analysis of reactive oxygen and nitrogen species in plasma-activated water, we attempted to separate the NO 2 − and HNO 2 concentrations depending on the pH value of aqueous solution by identifying their different features of absorption spectra within deep-UV and near-UV ranges. For the measurement of O 3 , we examined the molar absorption coefficient ε at 260 nm using two methods. In the first method, the absorption of degassed O 3 from water was measured, whereas in the second method, using an aqueous reaction of O 3 with NO 2 − , the decrease in O 3 was compared to the decrease in NO 2 − and increase in NO 3 − . The values of ε derived from both methods were slightly different, but were within ±5% of the value of 3.0 × 10 3 M −1 cm −1 , as commonly found in the literature. The reactive uptake of O 3 on aqueous solution of NaNO 2 was also estimated.