Determination of isotope ratios in the natural gas components CH4 and N2 separated by gas chromatography

To determine stable-isotope ratios of natural gas components a system is constructed to separate CH₄ and N₂ from milliliter quantities of natural gas by gas chromatography. Having passed through the separation column and a catharometer detector the gas flow is distributed consecutively into two lines, one in which N₂ is trapped in a helium cryostat at 4.2 K and one in which CH₄ is immediately combusted by CuO to CO₂ and H₂O which are trapped separately.The δ ²H-, δ ¹³C- and δ ¹⁵N-values are determined by conventional isotope mass spectrometry.