Figure 3.

Ion current (arbitrary scale) at m/z 44 using the membrane inlet mass spectrometer observed using solutions of known CO₂ content. Solutions containing CO₂ were prepared from step additions resulting in 0.25 mM increments of K₂CO₃ into concentrated acetic acid (pH 2) and 25 °C. Peak heights were recorded when equilibrium was reached. The average of three repetitions with standard deviations was 3% at 4.8 mM CO₂, 8% at 3.0 mM CO₂, and 10% at 0.4 mM CO₂. The solid line is a least-squares fit with a correlation coefficient of 0.999.