Identification of oxidation states of metal oxides by MALDI-TOF MS

For the detection of inorganic species, we have developed chemical reaction laser desorption ionization mass spectrometry, and applied it to the analysis of metal oxides in different oxidation states. Metal oxide species insoluble in common organic solvents were finely grounded in a mortar and suspended in a solvent. The turbid suspension was placed on a sample holder on which a suitable chelating reagent had been previously spotted in a similar manner for sample preparation employed in the matrix-assisted laser desorption mass spectrometry (MALDI-MS). By using this method, the mass spectra of manganese (II and IV) oxides (MnO and MnO₂), cobalt (II and III) oxides (CoO and Co₂O₃), and chromium (III and VI) oxides (Cr₂O₃ and CrO₃) were successfully obtained. By adjusting the experimental conditions, such as ionization modes and chelating reagents, the non-identical mass spectra were obtained for the elements in the different oxidation state. Thus, the oxidation states could be identified clearly.     

FFT analysis of atmospheric trace concentration of N2O continuously monitored by gas chromatography and cross-correlation to climate parameters

To investigate the characteristics of N₂O concentration, we applied several types of time series analyses such as fast Fourier transform (FFT), auto-correlation, and cross-correlation, to 2.5-year time series data of trace N₂O concentration continuously monitored by gas chromatography and meteorological data, measured in an urban area of Nagoya. It was found that there is a positive correlation between atmospheric N₂O concentration (ppbv) and, both steam pressure (hPa) and temperature (°C). In addition, negative and positive correlations in atmospheric pressure and in solar flux were also found, respectively. These findings suggest an enrichment of N₂O through environmental steam during the summer season, particularly in urban areas. On the other hand, the correlation to wind direction shows a variation with amplitude of 7 ppbv, from the north-west to the south-east, and a seasonal variation up to 12 ppbv, from winter to summer. These results support the hypothesis that atmospheric steam controls the N₂O concentration in urban areas. In addition, the correlation with wind direction suggests the existence of an emission source in the direction of seaside areas.