Creation of a cryogenic, inert atmosphere sample curation facility: update
Introduction: As reported previously  we have established a cryogenic facility for curation and handling of planetary materials at the University of Alberta. Established in order to enable curation and handling of the organic-rich Tagish Lake meteorite [e.g., 2], the facility consists of a state-of-the art Ar gas glove box, housed within a -20 °C controlled environment chamber. The Ar gas is purified with an MB 20 G gas purifier (MBraun, Inc.) and continually recirculated. A Class 1000 clean room serves as a room temperature anteroom and source of clean air for the -20 °C chamber. Results of ongoing studies of baseline contaminants and operating parameters are reported here. Effect of temperature on volatile organics: The glove box atmosphere was previously sampled using a solid phase microextraction fibre (SPME), exposed for 28 days at room temperature (Sept. 29 to Oct. 27, 2011). GC-MS analysis of the SPME fibre revealed common organic chemicals such as styrene and aniline . To test our hypothesis that low temperatures should lead to lower levels of organic vapours in the glove box atmosphere, an SPME fibre was stored in the glove box at the standard operating temperature of -20 °C for a period of 54 days (Sept. 26 to Nov. 19, 2012). GC-MS analysis on the fibre revealed that styrene and aniline were absent in the low temperature sample. Apparently, the combination of a lower temperature and decreasing rate of outgassing from glove box components over time combined with repeated flushing of the box with Ar gas effectively eliminated the vast majority of the vapor phase organic contaminants from the box. The evolution of the composition of the atmosphere over the next 10-12 months will be monitored by periodic sampling with SPME fibres. Glove composition: The original HypalonTM gloves provided with the glove box were found to be too stiff for at the nominal -20 °C operating temperature. They were subsequently replaced with gloves made from polyurethane, which retains serviceable elasticity down to -20 °C. In order to determine the nonvolatile organic residue on the surface of the new polyurethane gloves, the drippings from the passage of approximately 1 mL of ultrapure dichloromethane over a 2 cm x 2 cm piece of polyurethane glove material was analyzed by GC-MS. Not surprisingly, the GC trace of the glove dichloromethane rinse was found to contain the two monomeric species, viz. methylene diphenyl diisocyanate and 2,2'-(1,4-butanediyl)bis-oxirane, from which the polyurethane polymer material that forms the basis of the gloves was derived. Clearly, a dichloromethane rinse of the gloves prior to their installation is essential to stop the transfer of these nonvolatile organics to the interior of the glove box and ultimately the surfaces of any planetary materials being processed therein. References:  Hilts R.W. et al. 2012. Meteoritics & Planetary Science 47:A186.  Herd C.D.K. et al. 2011. Science 332:1304-1307.
Presented July 29-August 2, 2013 at the 76th Annual Meteoritical Society Meeting in Edmonton, Alberta.
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