On-line quantitative determination of2H/1H isotope ratios in organic and water samples using an elemental analyser coupled to an isotope ratio mass spectrometer

Abstract

A rapid continuous‐flow technique for the quantitative determination of hydrogen isotope ratios in organic materials and water, at natural abundance levels, is described. Samples are pyrolysed in a helium stream at 1080°C over an inert form of carbon. Hydrogen is separated from the other pyrolysis gases by gas chromatography and enters the ion source of the isotope ratio mass spectrometer (IRMS) via a crimp. The 2H/1H ratio of the gas was determined by the simultaneous integration of the m/z 2 (1H1H) and m/z 3 (2H‰1H) ion beams over time. δ2H‰ values of organic and water samples were determined by comparison with organic and water standards, respectively. The precision of the on‐line δ2H‰ measurement is <3.3‰. The accuracy of the method was demonstrated by the analysis of a laboratory standard water (NTW), a European Community Bureau Reference material, N,N‐tetramethylurea (TMU) and an International Atomic Energy Association polyethylene reference material (IAEA‐CH‐7). The measured values were NTW ‐39.4‰, TMU ‐144.1‰ and IAEA‐CH‐7 ‐100.7‰ (reference values are NTW ‐38.5‰, TMU ‐147.4‰ and IAEA‐CH‐7 ‐100.3‰). No apparent memory effect was observed when measuring samples at the natural abundance level. Calibration of organic measurements with water reference materials did not give satisfactory results, probably owing to differences in their respective pyrolysis pathways. The potential of the technique for food analysis was demonstrated by measuring the δ2H‰ values of vanillin samples derived from natural and synthetic sources and by the analyses of hexamethylenetetramine synthesized from beet, cane and apple juice sugars. © Crown copyright 1998. Reproduced with the permission of the Controller of Her Majesty’s Stationery Office.

Memory effect in deuterium analysis by continuous flow isotope ratio measurement

“…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.…”

“…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.…”

High‐throughput simultaneous determination of plasma water deuterium and 18‐oxygen enrichment using a high‐temperature conversion elemental analyzer with isotope ratio mass spectrometry

“…The on‐line determination of the 2 H 1 H/ 1 H 1 H isotope ratios and C 18 O/C 16 O was performed using a high‐temperature conversion elemental analyzer (TC‐EA) coupled with a Delta Plus XL isotope ratio mass spectrometer via a Conflo‐III Interface (ThermoFinnigan MAT, Bremen, Germany). The reactor consists of a carbon tube with carbon filling, ensuring that neither samples nor reaction gases can come in contact with oxygen‐containing compounds such as aluminium oxide while at high temperature 16. The following conditions were used: reactor temperature 1450°C, GC column temperature 90°C, helium flow 120 mL/min, and two references gases, hydrogen 57 and carbon monoxide 57.…”

“…Continuous‐flow isotope ratio mass spectrometry (CF‐IRMS) systems are designed for high productivity and to streamline the lengthy procedures associated with off‐line sample preparation and dual‐inlet mass spectrometry measurements, by employing a helium carrier to transport the gas to be measured from the preparation device into the directly coupled isotope ratio mass spectrometer. CF‐IRMS has been steadily developed to allow precise and rapid determination of nitrogen,11 carbon,12 oxygen13–15 and of hydrogen 16. This paper presents a method for simultaneous and reliable measurement of deuterium and 18 O of water samples using a high‐temperature conversion elemental analyzer (TC‐EA), which transforms water into HD and carbon monoxide gases that are then transferred on‐line into the isotope ratio spectrometer.…”

Hydrogen Isotopic (D/H) Composition of Organic Matter During Diagenesis and Thermal Maturation

“…The process is variously known as pyrolysis, thermal conversion (TC), and high-temperature reduction. The two most common preparative devices in continuous-flow analysis are the elemental analyzer for bulk samples (Kelly et al 1998), and the gas chromatograph for compound-specific analyses (Hilkert et al 1999).…”