Isotopic disproportionation during hydrogen isotopic analysis of nitrogen-bearing organic compounds

摘要: Rationale High-precision hydrogen isotope ratio analysis of nitrogen-bearing organic materials using high-temperature conversion (HTC) techniques has proven troublesome in the past. Formation reaction products other than molecular (H2) been suspected as a possible cause incomplete H2 yield and isotopic fractionation. Methods The classical HTC reactor setup modified version including elemental chromium, both operated at temperatures excess 1400 °C, have compared selection compounds, caffeine. A focus experiments was to avoid or suppress cyanide (HCN) formation reach quantitative yields. The technique also optimized provide acceptable sample throughput. Results The number selected compounds exhibited yields from 60 90 %. Yields close 100 % were measured for with chromium-enhanced reactor. δ2H values substantially different between two types experiments. For majority studied, highly significant relationship observed amount missing nitrogen atoms molecules, suggesting pyrolytic HCN byproduct. similar linear found result, reflecting fractionation. Conclusions The produce high presence glassy carbon is not suitable compounds. Adding chromium zone improves most cases. initial accompanied by strong effect, results on being shifted more negative values. can be understood an disproportionation leading HCN-hydrogen systematically enriched 2H 50 ‰. In chromium-containing solid residues are formed quantitatively. Copyright © 2015 John Wiley & Sons, Ltd.