Browsing by Author "Skelhorne, Aaron W."

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    Cold curation of pristine astromaterials: insights from the Tagish Lake meteorite
    (2016) Herd, Christopher D. K.; Hilts, Robert; Skelhorne, Aaron W.; Simkus, Danielle N.
    The curation and handling of volatile-bearing astromaterials is of prime importance in current and future plans for sample return missions to targets containing organic compounds, ices, or other volatile components. We report on the specific curation constraints required for the preservation of the Tagish Lake meteorite, a C2 ungrouped chondrite that contains significant concentrations of organic matter, including compounds of prebiotic interest or volatile in character, and which was recovered from a frozen lake surface a few days after its fall. Here we review the circumstances of the meteorite’s handling, its complement of intrinsic and contaminant organic compounds, and an unusual reaction between some of the specimens and the Al foil in which they were enclosed. From our results we derive the requirements for curation of the meteorite, and describe a specialized facility that enables its curation and handling. The Subzero Facility for Curation of Astromaterials consists of a purified Ar glove box enclosed within a freezer chamber, and enables investigations relevant to curation of samples at or below -10 °C. We provide several recommendations based on insights obtained from the commissioning and initial use of the facility that are relevant to collection of freshly fallen meteorites, curation of volatile-bearing meteorites and other astromaterials, and planning and implementation of curation plans for future sample return missions to volatile-bearing targets.
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    Creation of a cryogenic, inert atmosphere sample curation facility: establishing baselines for sample return missions
    (2012) Herd, Christopher D. K.; Hilts, Robert; Skelhorne, Aaron W.
    A new facility for handling and curiation of meteorites within a sub-zero environment under an Ar atmosphere has been established. Baseline contaminants within the glovebox containing the astromaterials will be described.
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    Creation of a cryogenic, inert atmosphere sample curation facility: update
    (2013) Hilts, Robert; Skelhorne, Aaron W.; Herd, Christopher D. K.
    Introduction: As reported previously [1] 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 [1]. 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: [1] Hilts R.W. et al. 2012. Meteoritics & Planetary Science 47:A186. [2] Herd C.D.K. et al. 2011. Science 332:1304-1307.
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    Development of a GC-MS-SPME method for the determination of amines in meteorites
    (2016) Hilts, Robert; Skelhorne, Aaron W.; Simkus, Danielle N.; Herd, Christopher D. K.
    A GC-MS-SPME analytical method for the direct determination of amines in aqueous solution has been developed. The key step in the procedure is the conversion of the amines into their non-volatile ammonium salts by protonation with HCl.
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    Development of a new SPME-GCMS method for the determination of amines in meteorites
    (2016) Hilts, Robert; Skelhorne, Aaron W.; Herd, Christopher D. K.; Simkus, Danielle N.
    Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino acids. It has been proposed that meteoritic amines are produced by the thermal decarboxylation of amino acids[1]. The analysis of amines using GC-MS techniques has proven to be problematical owing to the high water solubility and high volatility of these compounds. In addition, the strong interactions of polar amine molecules with the stationary phase of a typical polysiloxane column lead to extensive tailing, poor resolution of peaks and low detector response [2]. To circumvent these disadvantages the highly polar amines have been converted to less polar derivatives that are more amenable to GC analysis by substitution of amine N-H hydrogens with weakly polar moieties such as acyl, silyl, dinitrophenyl and methyl groups [2]. The derivatives of amines generally have much weaker interactions with stationary phases and thus are more volatile in terms of their chromatographic behavior, which leads to better separation on the column. In the last decade base-deactivated columns that give good separations of underivatized aliphatic and aromatic amines have been successfully developed [3]. Consequently, volatile amines in aqueous media can now be routinely and reproducibly analyzed by the combination of SPME(solid- phase microextraction) techniques with base-deactivated GC columns that have been specifically engineered to directly separate amines(see for example [4]). The great advantage of this analytical method is that it sidesteps derivatization,which invariably entails the loss of amines, especially those that are more volatile, through side reactions and incomplete transfer during isolation and workup. Results and Discussion: An aqueous test solution containing an in-house collection of amines standards, viz. N-ethylaniline (100 ppm), dipropylamine (100 ppm), methylamine (100 ppm) and piperidine (100 ppm) was prepared in 80 mL of Millipore water. The majority of this solution (70 mL) was set aside for SPME-GC(CP Volamine)MS analysis while the remaining 10 mL was adjusted to ca. pH = 2 using concentrated HCl to convert all of the amines into their corresponding, non-volatile ammonium salts. The water from this acidified mixture was removed on a rotary evaporator , affording a colourless residue. The solid was dissolved in ca. 3 mL of Millipore water and the pH was brought up to 8 by adding ca. 1 mL of 8 M NaOH(aq). The SPME –GC(CP-Volamine) trace of the reconstituted amine mixture was found to contain the same four amine standards as were seen in solution prior to the protonation step. Thus, this result proves that our amine to ammonium to amine methodologycan be used for the direct determination of volatile alkyl amines and aromatic amines. Application of our new SPME-GC(CP-Volamine)MS method to an aqueous extract of a 2-gram sample of the Tagish Lake stone10a afforded a GC trace that contained three different polar aromatic compounds, namely acetophenone , 4-phenylpyridine and 2-phenyl-1,2-propane diol. In the absence of any isotope ratio data, we cannot conclude whether these three aromatic species are indigenous or terrestrial contaminants. It should be pointed out, however, that acetophenone, has been liberated from the Tagish Lake meteorite by the application of heat [5], and thus it does not seem unreasonable to conclude that the acetophenone seen in the trace for 10a likely has an extraterrestrial origin. References: [1] M.A. Sephton, Astronomy and Geophysics, Vol. 45(2), p. 2.8-2.14 (2004). [2] H. Kataoka, Journal of Chromatography A, 733 (1996) 19-34. [3] "An Advanced Base Deactivated Capillary Column for analysis of Volatile amines, Ammonia and Alcohols.", Jaap de Zeeuw, Ron Stricek and Gary Stidsen, Restek Corp. Bellefonte, USA. [4] L. Muller, E. Fattore and E. Benfenati, Journal of Chromatography A, 791 (1997), 221-230. [5] H. Yabuta, G.D. Cody and C.M.O.D. Alexander (2007). Abstract # 2304, 38th Lunar and Planetary Science Conference.