New on-line methods for determining the deuterium/hydrogen composition of water and hydrocarbon gases using O^2- ion-conducting solid electrolyte reactor

Rationale: The deuterium/hydrogen (D/H) composition of water and hydrocarbon gases is widely used in geological, environmental and petroleum studies. The aim of this work was to develop a simple reduction zirconium dioxide solid electrolyte reactor (SER) for water decomposition and new methods for measuring hydrogen isotope ratios in water and hydrocarbon gases. Methods: δ²H_VSMOW values were determined using two new different on-line methods: solid electrolyte reactor isotope ratio mass spectrometry (SER-IRMS) for water and gas chromatography combustion solid electrolyte reactor isotope ratio mass spectrometry (GC-C-SER-IRMS) for hydrocarbon gases. Results: We have designed a solid electrolyte reactor based on oxygen ion-conducting zirconium dioxide stabilized by yttria (Y ₂O₃). The reactor was used for catalytic electrochemical decomposition of water in a helium carrier gas. The solid electrolyte reactor has a small internal volume of 0.1 cm³. It was operated at a temperature of ∼950 °C. The total time of analysis for determining the hydrogen isotope ratio in water was 150 s. A typical water sample volume was about 0.2 μL (split ratio 500:1). The precision of the δ ²H_VSMOW measurements for water was better than or equal to 2.2‰ and that for hydrocarbon gases was within 0.5-3.0‰. CONCLUSIONS Fast, simple and accurate on-line methods (SER-IRMS and GC-C-SER-IRMS) were developed. The SER-IRMS method makes it possible to work with small water samples. Although the GC-C-SER-IRMS method was developed for hydrocarbons, it can also be used for other organic gases and their mixtures. The new solid electrolyte reactor for water decomposition is low cost and the ceramic tube is inexpensive.