Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry
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Abstract
An anomalous stable hydrogen isotopic fractionation of 4 ‰ in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN2) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) δ2H reproducibility (1& sigma; standard deviation) of nine local isotopic reference waters analyzed daily improved substantially from about 1‰ to 0.58 ‰. This isotopically fractionating mechanism might affect other isotope-ratio mass spectrometers in which LN2 is used as a moisture trap for gaseous hydrogen
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry |
| Series title | Analytical Chemistry |
| DOI | 10.1021/ac101570f |
| Volume | 82 |
| Issue | 18 |
| Year Published | 2010 |
| Language | English |
| Publisher | ACS Publications |
| Publisher location | Washington, D.C. |
| Contributing office(s) | Branch of Regional Research-Eastern Region, Toxic Substances Hydrology Program |
| Description | 3 p. |
| First page | 7849 |
| Last page | 7851 |
| Country | United States |
| Google Analytic Metrics | Metrics page |