Precision trace cas analysis by FT-IR spectroscopy. 1. Simultaneous analysis of CO2, CH4, N2O, and CO in air

We report the development of a method of trace gas analysis based on 1-cm(- 1) resolution Fourier transform infrared (FT-IR) spectroscopy, deployable i n both laboratory and held applications. Carbon dioxide, methane, nitrous o xide, and carbon monoxide may be analyzed simultaneously in a single air sa mple using this method, We have demonstrated that the method can provide an alytical precision of the order of +/-0.15 mu mol mol(-1) for CO2, +/-0.9 m nol mol(-1) for CH4, +/-0.3 nmol mol(-1) for N2O, and +/-0.3 nmol mol(-1) f or CO, expressed as mole fractions in dry air. The analytical precision is in all cases competitive with or superior to that of the more usual methods of analysis for these trace gases, namely, nondispersive infrared spectros copy for CO2 and gas chromatography-based techniques for CH4, N2O, and CO. The novel FT-IR method relies on calibration using synthetically calculated absorbance spectra and a chemometric multivariate calibration algorithm, c lassical least squares.