Application of gas chromatography-combustion-isotope ratio mass spectrometry to carbon isotopic analysis of methane and carbon monoxide in environmental samples

Abstract A method for the determination of isotopic composition by combined gas chromatography-combustion-isotope ratio mass spectrometry was examined in order to measure the stable carbon isotope ratios of methane and carbon monoxide in environmental samples. The factors causing deviations in the observed value of δ 13 C were studied by analysis a mixed gas sample using different furance temperatures and sample amounts. The calibration procedure for correcting the measured value is described in detail. The carbon isotopic abundances of gases from biomass burning were determined. A single determination with an accuracy of ca. 0.5‰ as δ 13 C took about 10 min. The sample consumption was about 0.2 μl at standard temperature and pressure. The proposed method is simpler and faster than other procedures, permitting a large number of samples to be analysed within a short time while only a small amount of sample is consumed.