APPLICATION OF GAS-CHROMATOGRAPHY COMBUSTION-ISOTOPE RATIO MASS-SPECTROMETRY TO CARBON ISOTOPIC ANALYSIS OF METHANE AND CARBON-MONOXIDE IN ENVIRONMENTAL-SAMPLES

A method for the determination of isotopic composition by combined gas chromatography-combustion-isotope ratio mass spectrometry was examine d in order to measure the stable carbon isotope ratios of methane and carbon monoxide in environmental samples. The factors causing deviatio ns in the observed value of delta(13)C were studied by analysing a mix ed gas sample using different furnace temperatures and sample amounts. The calibration procedure for correcting the measured value is descri bed in detail. The carbon isotopic abundances of gases from biomass bu rning were determined. A single determination with an accuracy of ca. 0.5 parts per thousand as delta(13)C took about 10 min. The sample con sumption was about 0.2 mu l at standard temperature and pressure. The proposed method is simpler and faster than other procedures, permittin g a large number of samples to be analysed within a short time while o nly a small amount of sample is consumed.