Quantitative gas composition analysis method for a wide pressure range up to atmospheric pressure-CO₂ plasma case...

A mass spectrometer with a custom sampling system comprising one fixed and one variable orifice is presented. The custom sampling system allows the determination of the gas composition in the pressure range from 5 mbar to 1000 mbar, with low gas-demixing (<1.5%). A case study of mass spectrometer optimization and calibration for the measurement of relative concentration of CO₂, CO, O₂, and N₂ gases is presented, together with an example of the CO₂ conversion at a microwave plasma torch. The absolute error of the measured conversion of CO₂ in CO is found to be less than 1.6% in the complete pressure range. The conversion determination routine presented here allows us to determine relative molar flows of CO₂, CO, O₂, and N₂ and to distinguish between CO and N₂ gases, which is important for the determination of the CO₂ conversion in the case of air impurities or in the case of CO₂/N₂ mixtures.