13:30 〜 15:30
▲ [16p-P5-2] Measurement of Oxygen Radicals using Ambient Mass Spectrometry
キーワード：oxygen radical, ambient mass spectrometry
The use of non-thermal atmospheric pressure plasma is drawing attention in wide range of biomedical applications. Recently, by using a commercially available oxygen or nitrogen radical source (Tough Plasma, Fuji Machine MFG Co. Ltd.), we have investigated the effects of radical treatment on either the cell proliferation or bacterial inactivation. Hashizume et al revealed a substantial influence of the atomic oxygen [O (3Pj)] on the inactivation of Penicillium digitatum spores. In addition, the absolute density of O (3Pj) measured by a vacuum ultraviolet absorption spectroscopy was on the order of 1013-1014 cm-3.
In this study, an ambient mass spectrometry was applied to measure atomic oxygen density generated from Tough Plasma. The radical source produced only oxygen radicals due to the simple gas mixture of a small amount of O2 in Ar and we used a state-of-the-art ambient mass spectrometer (HR60-EQP, Hiden Analytical) to detect the oxygen signal. The mass spectrometer was operated in the RGA mode with an internal electron source, which allows production of positive ions by electron-impact ionization. Firstly, for the measurement of absolute O2 molecular density employing Ar/O2 mixture without plasma, two different tuning conditions were used for finding an optimized condition of electron energy. Then, electron energy scans were performed for atomic oxygen (m/z 16) with and without plasma. The absolute density of atomic oxygen was derived with the measured difference of the intensities with and without plasma near the optimized electron energy by taking the known gas density (2.145×1019 cm-3 at a standard atmosphere) into account. From the calibration with the density of known mole fractions of mixed gas, the density of atomic oxygen was estimated to be 9.90×1013 cm-3.
In this study, an ambient mass spectrometry was applied to measure atomic oxygen density generated from Tough Plasma. The radical source produced only oxygen radicals due to the simple gas mixture of a small amount of O2 in Ar and we used a state-of-the-art ambient mass spectrometer (HR60-EQP, Hiden Analytical) to detect the oxygen signal. The mass spectrometer was operated in the RGA mode with an internal electron source, which allows production of positive ions by electron-impact ionization. Firstly, for the measurement of absolute O2 molecular density employing Ar/O2 mixture without plasma, two different tuning conditions were used for finding an optimized condition of electron energy. Then, electron energy scans were performed for atomic oxygen (m/z 16) with and without plasma. The absolute density of atomic oxygen was derived with the measured difference of the intensities with and without plasma near the optimized electron energy by taking the known gas density (2.145×1019 cm-3 at a standard atmosphere) into account. From the calibration with the density of known mole fractions of mixed gas, the density of atomic oxygen was estimated to be 9.90×1013 cm-3.