Real time monitoring of gases emitted from soils using a multi-turn time-of-flight mass spectrometer “MULTUM-S II”

Abstract

Many miniaturized mass spectrometers used for on-site analysis have been designed and developed recently utilizing a broad range of analyzer platforms. These instruments are expected to have widespread applications covering many fields of interest. In our laboratory, a miniaturized multi-turn time-of-flight (TOF) mass spectrometer “MULTUM-S II” was designed and constructed. The size and weight of the developed “MULTUM-S II” are 45 cm × 23 cm × 64 cm and 36 kg. Irrespective of this small platform, it still boasts a high mass resolution capability of more than 30 000. In this study, we attempted to carry out real-time monitoring of gaseous compounds such as N₂, O₂, CO₂, N₂O and CH₄. Using conventional miniaturized mass spectrometers, CO₂ and N₂O cannot be detected simultaneously due to the low mass resolution inherent to these established analyzer designs. Using a new method, “GC/high resolution mass spectrometry” described in this paper, real time monitoring of gases emitted from soils can be achieved. In a soil incubation experiment, CO₂ and N₂O started to increase just after water supplement and these gases varied similarly during the experiment, thus showing that this improved gas analyzing system could monitor the short time response of gaseous production in soil.