CO2 concentration measurements on air samples by mass spectrometry

A new technique for measuring CO2 concentration in air samples, based on ma ss spectrometry, is described as an alternative to the common gas chromatog raphic method. Using a dual inlet isotope ratio mass spectrometer (IRMS), t he ratio of the abundances of the m/z peaks 44 and 28 is determined, The pr ecision of measurements (standard deviation <3 ppmv) is generally as good a s the analysis with gas chromatography for small air samples (<1 ml STP of air). A major advantage of this new method is the possibility of parallel e lemental and isotopic measurements of many air components. The technique is further improved by new wide mass range mass spectrometers allowing simult aneous intensity measurements of several m/z values between 28 and 44, resu lting in an uncertainty of <0.5 ppm. The precision is somewhat limited by t he production of N2O and NO2 from N-2 and O-2 in the ion source, which acco unts for about half of the signal strength at m/z 44. Copyright (C) 2000 Jo hn Wiley & Sons, Ltd.