PREPARATION OF ORGANIC AND WATER HYDROGEN FOR STABLE ISOTOPE ANALYSIS - EFFECTS DUE TO REACTION VESSELS AND ZINC REAGENT

Combustion of organic matter in sealed Pyrex, Vycor, and quartz ampules at temperatures between 520 and 900-degrees-C yields less than stoichiometric amounts of water. The loss of hydrogen to hydration reactions between water vapor and glass/quartz interferes with the determination of C/H and N/H elemental ratios in organic matter. The effect increases from quartz to Vycor to Pyrex, but the incomplete yield does not significantly affect the precision and accuracy of the determination of stable hydrogen isotope ratios. Reactions between water and Pyrex do not affect the conversion of water to hydrogen with zinc in Pyrex ampules at 500-degrees-C, which is quantitative, but even preoutgassed zinc contains a deuterium-depleted hydrogen blank. D/H ratios in hydrogen from the Zn method require a nonlinear correction to achieve compatibility with deltaD values from the uranium method.