Proposal for an in situ measurement of the atmospheric methane concentration using a high-resolution quadrupole mass spectrometer

Abstract An in situ , real time measurement of the methane (CH 4 ) concentration in the earth's atmosphere using a high-resolution quadrupole mass spectrometer (QMS) has been proposed. CH 4 is a strong greenhouse gas that causes warming of the earth's surface. Therefore, the measurement of the atmospheric CH 4 concentration is essential. The high-resolution QMS is equipped with normal and high resolution modes. In the normal mode, the Mass15 Mass14 peak ratio was measured for the CH 4 concentration of 0–0.08% in volume to obtain the calibration curve and the measured curve showed good linearity and traceability. In addition, in the high resolution mode, the measurement of the CH 3 + 15 N + peak ratio was proposed to evaluate the CH 4 concentration lower than approximately 0.02% with a wide dynamic range. The CH 3 + (15.0235 u) peak has been successfully separated from a 15 N + (15.0001 u) peak that is a gathering of minor isotropic ions of nitrogen. An overall CH 4 concentration range we can measure is predicted to 0.001–30% by using the normal and high resolution modes.