A 1-10 mg portion of water is reduced with Zn metal in a sealed tube at 450 /sup 0/C to prepare hydrogen for isotopic analysis. After reaction the tube is attached directly to the mass spectrometer without further processing. Replicate analyses of water samples give reproducibility of 0.2-0.4% (1sigma); fluid inclusion samples, 1.9%; and water of hydration of gypsum, released and reduced in the sealed tube, 1.1%. A batch of 10 samples can be prepared in 1 h.

Reduction of water with zinc for hydrogen isotope analysis

The hydrogen and carbon isotopic composition of methane from natural gases of various origins

Stable isotope studies of hydrogen and oxygen stable isotope ratios of water within plants are providing new information on water sources, competitive interactions and water use patterns under natural conditions. Variation in the utilization of summer rain by aridland species and limited use of stream water by mature riparian trees are two examples of how stable isotope studies have modified our understanding of plant water relations. Analyses of xylem sap and tree rings have the potential of providing both short-term and long-term information on plant water use patterns.

Water uptake by plants: perspectives from stable isotope composition

Liquid-vapor fractionation of oxygen and hydrogen isotopes of water from the freezing to the critical temperature

To calibrate infrared (IR) spectroscopy for quantitative analysis of trace structural OH in specific minerals, we have determined concentrations of H in pure separates of mantle derived pyrope garnet (56 ± 6 ppm H_2O by weight), augite (268 ± 8, ppm H_2O, and enstatite (217 ± 11 ppm H_2O) by manometry after heating the samples and extracting H_2 gas under vacuum. IR spectroscopy confirmed the presence of intrinsic OH in these samples prior to extraction and indicated between 86 and 100% removal of H during the extraction procedure. The integral specific absorption coefficients of 1.39 ± 0.14(lσ),7.09
± 0.32, and 15.6 ± 0.94 /(ppm H_2O.cm^2) for pyrope, augite, and enstatite, respectively, allow precise spectroscopic determination of the OH content of upper mantle garnets and pyroxenes to concentration levels of a few parts per million. Uncertainties in accuracy depend on mineral composition and characteristics of the OH absorption spectrum and are estimated to range between ± 10 and ± 50%.

http://minsocam.org/msa/ammin/toc/articles_free/1995/bell_p465-474_95.pdf

Jacob Bigeleisen

Papers

Conversion of Hydrogenic Materials to Hydrogen for Isotopic Analysis