oa Stability of the Hydrogen Isotope Ratio in a Hydrogen Gas Standard Stored in Sampling Cylinders

Hydrogen (H2) is a gas with high energy potential, considered a viable alternative to fossil fuels. Recently, it has been identified in various geological formations. Natural hydrogen, or geological hydrogen, can be found as free gas, inclusions in rocks, and dissolved in groundwater. The analysis of hydrogen isotopes can provide insights into geochemical processes and create isotopic reference standards. This work aimed to evaluate the stability of the isotopic composition of a gas mixture containing 2.5% hydrogen, 0.5% helium, and nitrogen, stored in Swagelok cylinders for analysis. The research showed that d²H-H2 values remained stable for up to 25 days, according to statistical analyses. However, after this period, there were indications of isotopic fractionation, possibly due to differential interactions of isotopes with cylinder surfaces, leaks, or unwanted chemical reactions. The outcomes of this investigation are crucial for improving gas sampling and storage in field and laboratory studies, minimizing errors in determining the genuine isotopic ratio of the analyzed gas.