Dual Stainless Steel Cryogenic Trap for Noble Gas Separation
The precise determination of noble gas concentrations and isotopic compositions is essential in geochemistry, cosmochemistry, and atmospheric research. In particular, krypton (Kr) and xenon (Xe) isotopes provide valuable insights into processes ranging from stellar nucleosynthesis to the evolution of Earth’s atmosphere. However, analytical accuracy is often limited by the need to separate krypton from both the far more abundant argon (Ar) and xenon prior to mass spectrometric analysis. The method presented by Péron et al. (2020) provides a highly efficient solution based on a dual stainless steel cryogenic trap system.
The technique uses cryogenic separation, in which gases are selectively condensed and subsequently released at defined temperatures according to their different vapor-pressure curves. At the heart of the system are two cryogenic traps connected in series, enabling a multistage distillation process. One trap collects the target component, while the second provides an additional purification stage.
A key innovation of the method is the use of electropolished stainless steel cryogenic traps. The material is mechanically robust, chemically inert, and virtually impermeable to gases. At the same time, the electropolished surface reduces adsorption effects and minimizes carryover, resulting in highly reproducible measurements.
Mounting both stainless steel traps on a shared cold head enables precise temperature control and reproducible thermal cycling. The gas mixture is condensed, released under controlled conditions, and distilled repeatedly between the two traps. This reduces unwanted co-trapping and increases the purity of the separated gas fractions.
In summary, the dual stainless steel cryogenic trap system offers high recovery, low contamination, and excellent reproducibility. Compared with conventional methods, it represents a significant advance in noble gas purification and preparation. In addition to this specialized system, conventional cryogenic traps using activated charcoal, stainless steel, or exchange-gas cooling are also available.
Source: Péron, S., Mukhopadhyay, S., and Huh, M. M. (2020). “A new dual stainless steel cryogenic trap for efficient separation of krypton from argon and xenon.” Journal of Analytical Atomic Spectrometry, 35(1), September 2020.
