A Gas Chromatographic Separation for the H and C Stable Isotope Ratio Determination of Coal Compounds

Abstract

A new, completely automated gas chromatography technique has been developed to separate the different gaseous compounds produced during underground coal gasification for their (13)C/(12)C and D/H isotope ratio measurements. The technique was designed for separation and collection of H(2), CO, CO(2), H(2)O, H(2)S, CH(4), and heavier hydrocarbons. These gaseous compounds are perfectly separated by the gas-phase chromatograph and quantitatively sent to seven combustion and collection lines. H(2), CO, CH(4), and heavier hydrocarbons are quantitatively oxidized to CO(2) and/or H(2)O. The isotopic analyses are performed by the sealed-tube method. The zinc method is used for reduction of both water and H(2)S to hydrogen for D/H analysis. Including all preparation steps, the reproducibility of isotope abundance values, for a quantity higher than or equal to 0.1 mL of individual components in a mixture (5 mL of gases being initially injected in the gas chromatograph), is ±0.1‰ for δ(13)C(PDB) and ±6‰ for δD(SMOW).

A new method for determining δ13C and δD simultaneously for CH4 by gas chromatography/continuous‐flow isotope‐ratio mass spectrometry

“…The most common technique used over the last 20 years has involved the collection of the H 2 O produced during the combustion step, which is subsequently passed through a reduction oven to generate H 2 for δ D determination. A variety of metals have been successfully used as reduction agents, for example, Zn,4–10 U,11,12 Cr,13,14 Mn15 and Ni 16,17. This technique generates reproducible δ D results between ±1 and 5‰.…”

Carbon stable isotope analysis as a tool for tracing temperature during the El Tremedal underground coal gasification at great depth

“…The d 13 C isotopic abundance is then measured using a mass spectrometer. The whole process from the gas separation to the isotopic measurements is described elsewhere [16].…”