1 Hydrogen Isotope Separation Using Gas Chromatography (original) (raw)
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Analytical Chemistry, 1995
Two instrumental approaches are described for continuous-flow high-precision determinations of D/H ratios from hydrogen gas or via on-line reduction of water. In the first system, Ar is used as a carrier gas, with a Ni reduction furnace and a water trap to remove minor levels of unreduced water that are a potential source of memory effects. Precisions of SD < 10%0 (GDs~ow) over a 6W%o range from-55 to +532%0 are obtained for liquid water (0.4 pL). Iinearity is excellent over 4 orders of magnitude of D concentration in tap water (9 > 0.9999), although precision degrades at enrichments GDs~ow > 5000%0. In the second system, a heated Pd metal foil functions as a mter to admit purified hydrogen into the mass spectrometer. Hydrogen gas injections are made into flowing Ar and are directed to the Pd filter (-330 "C) which passes hydrogen isotopes only while diverting the carrier flow to waste. Precisions of these measurements are SD < 6%0 over the D enrichment range-213 to 340%0, with excellent linearity (1.2 > 0,9999) and accuracy (<2%0). Similar precision is obtained using the on-line reduction apparatus and a water trap prior to the Pd filter with injections of 0.4 pL of liquid water, with acceptable linearity (1.2 > 0.999) over 3 orders of magnitude of D concentration. Neither system shows any sign of memory effects when water is analyzed. 'Ihe data indicate that either one of these systems is a useful means for continuous-flow IRMS of D/H isotope ratio determinations. High-precision gas isotope ratio mass spectrometry (GIRMS) has been the technique of choice for determination of isotopes of the light elements, H, C, N, 0, and S for several decades.' The classical dual-inlet approach is now accompanied by continuousflow methods, first developed for the interface of the isotope ratio mass spectrometer (WvlS) with gas chromatography (GC)? but now available for analysis of products of elemental analyzers3 and other mixtures such as breath: and more recently liquid chro-matograph~.~ The precision of continuous-flow methods a p proaches that of dual-inlet with more rapid analysis and often without the requirement for cumbersome pretreatment6
Rapid Communications in Mass Spectrometry, 2012
In recent experiments, we found that compound-specific d 2 H values can vary as a result of changing the gas chromatography temperature program under common pyrolysis conditions. To achieve better precision, it is necessary to examine the details and find a solution to this problem when using gas chromatography/thermal conversion/isotope ratio mass spectrometry (GC-TC-IRMS) for hydrogen isotope analysis. METHODS: A test was designed to find the possible temperature effect under four different GC temperature ramp rates using n-alkanes (n-C 21 , n-C 27 , and n-C 31) and fatty acids (n-C 12 , n-C 18 , and n-C 24). The common 'hexane' method was used initially to condition the pyrolysis reactor. Experiments were then carried out using the 'methane condition' method because it was considered to improve pyrolysis efficiency. RESULTS: Under the 'hexane condition' the measured hydrogen isotope ratios of the n-alkanes and n-fatty acids became more positive with increasing GC temperature ramp rate. The ion current intensity of hydrogen also generally increased. However, when the 'methane condition' method was used, the measured d 2 H values of the n-alkanes and n-fatty acids showed little change under different GC temperature ramp rates. CONCLUSIONS: Higher pyrolysis efficiency could reduce the tailing of the H 2 peak and the related isotopic variations at increased GC temperature ramp rates. In addition, too slow a temperature ramp rate could broaden the peak width and thus increase the background effect and possible isotopic fractionations in the split interface; this could also influence the hydrogen isotope values. We therefore suggest that the appropriate temperature ramp rate is an important factor in improving the precision in analyzing compound-specific hydrogen isotopes.
International Journal of Hydrogen Energy, 2013
Neutron radiography (NR) is compared with the commonly used carrier gas hot extraction (CGHE) technique. We performed isothermal hydrogen effusion experiments at 623 K to study the mass transport kinetics. The investigated material was technical iron. The quantification of the hydrogen mass flow is done for NR by using concentration standards. The temporal hydrogen concentration evolution in the sample coincides well for both methods, i.e. NR and CGHE, and is in good agreement with literature. The advantages of the NR method are the non-destructive nature of measuring and the in-situ determination of hydrogen concentrations with high spatial and temporal resolution. Remaining hydrogen inside the sample can be identified directly by the NR method.
Journal of Nuclear Science and Technology, 2002
Experiments on the separation of H 2 -HD isotopic gas mixture were performed with a 1,020 mm-height "Cryogenic-Wall" thermal diffusion column with a heated tube of 9.63 mm-outer-radius and a cooled tube of 14.21 mm-inner-radius which was cooled by liquid nitrogen. Abandance ratios of HD to H 2 in the feed, product and waste flow were measured by stable isotope mass spectrometer Finnigan MAT252.
Hydrogen isotope sensor using high temperature proton conductors
Solid State Ionics, 2004
EMF of the hydrogen isotope cell has been applied to the sensing of hydrogen isotopes. In this paper, the atomic hydrogen isotope composition and the total pressure of the hydrogen isotopes were determined simultaneously by use of two electrochemical cells with different kind of proton-conducting electrolytes. Among the several proton conductors, CaZr 0.9 In 0.1 O 3Àa and SrCe 0.95 Yb 0.05 O 3Àa were chosen for the sensor. The difference in EMFs of the two proton conductor cells was independent of the total pressure of hydrogen isotopes and, thus, served to determine the atomic hydrogen isotope compositions in gases.
Diffusible hydrogen measurement in welding consumables using a Nafion @117 based proton exchange membrane hydrogen sensor (PEMHS) has been carried out successfully at room temperature. For this measurement, the specimen preparation was done as per ISO 3690 by depositing steel welding electrodes with different levels of diffusible hydrogen. The results obtained in this measurement have shown one to one correlation with the mercury method as per the ISO 3690 Standard [1]. After demonstrating the diffusible hydrogen measurement at room temperature, the challenge was to use this sensor along with a system for hot extraction of diffusible hydrogen, so that the duration of measurement can be reduced as in the case of Gas Chromatography (GC) method. With this objective, a chamber for hot extraction of diffusible hydrogen was designed and fabricated. It is a cylindrical stainless steel chamber with an in situ heater and PID controller to control and maintain the temperature during hydrogen collection. Using this heater, specimen can be heated to maximum temperature of 500ºC while the chamber itself is maintained at ambient temperature by water cooling. The chamber has an inlet and an outlet for argon purging and pressurization.
Journal of Nuclear Science and Technology, 1988
The Chapman-Cowling (CC) formula as well as the Monchick-Sandler-Mason (MSM) formula for the thermal diffusion factor for H 2-HT gas mixture were examined through separative analysis by comparing experimental results of isotope separation using thermal diffusion column. The CC formula could not explain quantitatively the thermal diffusion between H2 and HT, whatever parameters and/or intermolecular model potentials we chose. The Lennard-Jones (9-6) potential was regarded as the most adequate one among the model potentials tested here for H 2-HT gas mixture. The MSM formula was approximated so as to be evaluated even when input data for the formula are not available. The inelastic collision integral ratios were also estimated roughly in two ways. Application of the MSM formula could have reduced discrepancies between experimental and analytical results although the estimates of the formula and the inelastic collision integral ratios were rough.
International Journal of Health Sciences (IJHS), 2022
Stable isotope analysis is a valuable tool in forensic investigation. Recently, isotopic investigation is in great trend, Forensic discipline is making use of multipurpose isotopic profiles along with isotopic landscapes or isoscapes from body tissues. These isotopes help in predicting the geographical location or origin of the unidentified body. Isotope analysis is a commendable and powerful tool for geolocation and can provide investigative leads to the investigating officer as well as forensic experts. This review article basically focuses on the hydrogen isotopes and their applications in forensic science. Being a bio-element, it is ubiquitous and has immense biological and chemical significance. We have discussed the 3420 role of hydrogen isotopes in different disciplines of forensic science such as forensic biology, wildlife forensics, forensic anthropology, forensic chemistry and toxicology etc. and the newer advancements that are employed in this discipline for making the analysis more accurate and robust. This field is still in its growing stage and hence, with more advancements, it will provide a great aid in forensic investigation.
Journal of Nuclear Science and Technology, 2004
A pressure-reducing method is used effectively in a water distillation process to enhance the equilibrium separation factor. The feasibility of the technique is established through application to a water-hydrogen chemical exchange process using a prototype separation column. Isotope separation experiments examining the water-hydrogen chemical exchange reaction are performed for column pressures of 12-101 kPa, and the separation factors for hydrogen and deuterium are obtained. The HETP (Height Equivalent to a Theoretical Plate) values were distributed in the range of 6 to 15 cm. By reducing the pressure in the column, the process temperature can be lowered without reducing the molar fraction of water vapor in the gas stream. It confirmed that the separation factors under reduced pressure are larger than under atmospheric pressure. This fact demonstrates the effectiveness of reduced pressure in water-hydrogen chemical exchange processes.