ABSTRACT

A flow-through system, GC/GC/C/IRMS (gas chromatograph/gas chromatograph/combustion/isotope ratio mass spectrometer) was developed for carbon isotope analysis of methane in a sample of low level concentration. In this system, methane was roughly separated from a large amount of N₂ and O₂ in the first GC with packed column, then introduced into GC/C/IRMS and carbon isotopic composition was measured. The δ¹³C of methane in a sample of 92 ml in volume with concentration of 11 ppm was successfully obtained with a standard deviation of ±0.4‰.