Deuterium/hydrogen isotope ratio measurement of water and organic samples by continuous‐flow isotope ratio mass spectrometry using chromium as the reducing agent in an elemental analyser

Abstract

A rapid continuous-flow technique for quantitative determination of hydrogen isotope ratios in water and organic materials at natural abundance levels is described. Water and organic samples were reduced in a helium stream at temperatures in excess of 1000 degrees C over chromium metal. delta(2)H per thousand values of water and organic samples were determined by calibration against International Atomic Energy Agency reference materials V-SMOW and SLAP water. The accuracy of the method was demonstrated through the analysis of the intermediate water standard GISP and IAEA water intercomparison materials OH-1, OH-2 and OH-3. Values obtained using this technique compared well with reference values (maximum difference 2.2 per thousand). The precision of water analyses was less than 2.3 per thousand (1 sigma or 1 standard deviation) in all cases. No apparent memory effect was observed when measuring samples at the natural abundance level. The application of the technique to organic molecules and the salts of organic acids was successfully demonstrated by measuring the delta(2)H per thousand values of an n-hexadecane laboratory reference and anhydrous calcium formate versus water calibration materials.

Memory effect in deuterium analysis by continuous flow isotope ratio measurement

“…However, some instances of the Ni and Cr reduction methods are reported to be absent of memory effects [19][20][21][22][23]. In contrast memory effects of the equilibrium technique are rarely reported [35][36][37], although Huber and Leuenberger [10] reports of memory effects of 2% for an equilibrium system.…”

“…Traditionally the two principal approaches of obtaining hydrogen gas for stable isotope ratio analysis are the reduction method using metals (e.g., Cr, Mn, Ni, Zn and U) and the equilibrium techniques between water and hydrogen gas. Both techniques have been used for offline and (semi) automated sample preparation methods [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Samples obtained by off-line hydrogen preparation are analysed by the classical dual inlet method, whereas for automatically prepared samples the dual inlet or the continuous flow (CF) methods are used in connection with an autosampler.…”

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

“…As an alternative to the HTC technique, chromium has been used in lieu of glassy carbon, albeit at lower reaction temperatures, usually around 1000 to 1100 °C . These systems have been applied mostly to water and for reducing gaseous compounds.…”

“…As an alternative to the HTC technique, chromium has been used in lieu of glassy carbon, albeit at lower reaction temperatures, usually around 1000 to 1100°C. [9,[21][22][23] These systems have been applied mostly to water and for reducing gaseous compounds. Armbruster and colleagues [23] added chromium powder to solid materials and modified a conventional elemental analyzer (EA) with a quartz/chromium bed, mainly to suppress HX (X = F, Cl, Br, I) formation during the analysis of halogenated compounds.…”

Routine hydrogen isotope measurement of cellulose nitrate by high‐temperature pyrolysis – reference materials and precision

“…Several recent papers have presented methods that are capable of determining the hydrogen isotope composition of different materials such as water, hydrous minerals, and complex organic materials. Hydrogen isotope measurements can be carried out on micro amounts of water and organic materials by offline6 or online7, 8 reduction over hot metal surfaces such as zinc or chromium. In addition to reduction, both low‐temperature9 and high‐temperature10–13 pyrolysis have been described as providing a reliable technique for determining the hydrogen isotopes of different materials.…”