Wolfram Thiemann

Amino acids from ultraviolet irradiation of interstellar ice analogues

Amino acids are the essential molecular components of living organisms on Earth, but the proposed mechanisms for their spontaneous generation have been unable to account for their presence in Earths early history. The delivery of extraterrestrial organic compounds has been proposed as an alternative to generation on Earth, and some amino acids have been found in several meteorites. Here we report the detection of amino acids in the room-temperature residue of an interstellar ice analogue that was ultraviolet-irradiated in a high vacuum at 12 K. We identified 16 amino acids; the chiral ones showed enantiomeric separation. Some of the identified amino acids are also found in meteorites. Our results demonstrate that the spontaneous generation of amino acids in the interstellar medium is possible, supporting the suggestion that prebiotic molecules could have been delivered to the early Earth by cometary dust, meteorites or interplanetary dust particles.

Distribution and balance of volatile halogenated hydrocarbons in the water and air of covered swimming pools using chlorine for water disinfection

Abstract A survey of the “chlorination practice” of swimming-pool waters is presented taking the case of covered pools in Bremen. Chlorination of water may result in specific health hazards by various halogenated chemicals. Trihalomethanes (THMs), among others, are determined in water and air samples. We succeeded in identifying one organic “precursor” of the synthesis of THMs in swimming pools. An estimate of the average and maximum burden of the user/swimmer is given. Short and long range alternative measures are proposed to diminish the health hazards. We conclude from this work that the application of chlorine for disinfection should be minimized.

Urea, Glycolic Acid, and Glycerol in an Organic Residue Produced by Ultraviolet Irradiation of Interstellar/Pre-Cometary Ice Analogs

More than 50 stable organic molecules have been detected in the interstellar medium (ISM), from ground-based and onboard-satellite astronomical observations, in the gas and solid phases. Some of these organics may be prebiotic compounds that were delivered to early Earth by comets and meteorites and may have triggered the first chemical reactions involved in the origin of life. Ultraviolet irradiation of ices simulating photoprocesses of cold solid matter in astrophysical environments have shown that photochemistry can lead to the formation of amino acids and related compounds. In this work, we experimentally searched for other organic molecules of prebiotic interest, namely, oxidized acid labile compounds. In a setup that simulates conditions relevant to the ISM and Solar System icy bodies such as comets, a condensed CH(3)OH:NH(3) = 1:1 ice mixture was UV irradiated at approximately 80 K. The molecular constituents of the nonvolatile organic residue that remained at room temperature were separated by capillary gas chromatography and identified by mass spectrometry. Urea, glycolic acid, and glycerol were detected in this residue, as well as hydroxyacetamide, glycerolic acid, and glycerol amide. These organics are interesting target molecules to be searched for in space. Finally, tentative mechanisms of formation for these compounds under interstellar/pre-cometary conditions are proposed.

Organic compounds on comet 67P/Churyumov-Gerasimenko revealed by COSAC mass spectrometry

Comets harbor the most pristine material in our solar system in the form of ice, dust, silicates, and refractory organic material with some interstellar heritage. The evolved gas analyzer Cometary Sampling and Composition (COSAC) experiment aboard Rosetta’s Philae lander was designed for in situ analysis of organic molecules on comet 67P/Churyumov-Gerasimenko. Twenty-five minutes after Philae’s initial comet touchdown, the COSAC mass spectrometer took a spectrum in sniffing mode, which displayed a suite of 16 organic compounds, including many nitrogen-bearing species but no sulfur-bearing species, and four compounds—methyl isocyanate, acetone, propionaldehyde, and acetamide—that had not previously been reported in comets.

UV-photoprocessing of interstellar ice analogs : Detection of hexamethylenetetramine-based species

The physical conditions governing the dense cloud environment are reproduced in a high vacuum experimental setup at low temperature T 12 K. The accretion and photoprocessing of ices on grain surfaces is simulated by depositing an ice layer on a cold finger, while it is irradiated by ultraviolet (UV) photons. After irradiation the sample is slowly warmed to room temperature; a residue remains, containing the most refractory products of photo- and thermal processing. In this paper we report on the analysis of the residues performed by means of gas chromatography-mass spectrometry (GC-MS). A number of new molecules based on hexamethylenetetramine (HMT, C 6 H 1 2 N 4 ), the most abundant component of the residues reported here, were detected: methyl-HMT (C 6 H 1 1 N 4 -CH 3 ), hydroxy-HMT (C 6 H 1 1 N 4 -OH), methanyl-HMT (C 6 H 1 1 N 4 -CH 2 OH), amin-aldehyd-HMT (C 6 H 1 1 N 4 -NH-CHO) and methanyl-aldehyd-HMT (C 6 H 1 1 N 4 -CHOH-CHO). To the best of our knowledge, this is the first reported synthesis of these molecules. Currently, these are the heaviest identified components of the residue. These species might also be present in the interstellar medium, given that the ice was submitted to high temperatures, of the order of 300 K, and form part of comets. Our work serves as preparation for the ESA-Rosetta mission, which plans to do in situ analysis of the composition of a comet nucleus with the COSAC instrumentation.

The COSAC experiment on the lander of the ROSETTA mission

Abstract The COSAC experiment on the Lander of the ESA mission ROSETTA is aimed at the in situ investigation of matter of a cometary nucleus (P/Wirtanen) with respect to its chemical and isotopic composition. Special emphasis is put on the identification of complex organic molecules including their chirality. The instrument, presently under development, will employ for analysis a multi-column gas-chromatograph and a high-resolution TOF mass spectrometer. These instruments can be controlled from ground and used either separately or in the GC/MS coupling mode. They are suited for analysis of the natural cometary atmosphere or pyrolytically generated gas from surface or near-surface samples.

Atmospheric deposition of triazine herbicides in Northern Germany and the German Bight (North Sea)

12 organonitrogen and -phosphorus pesticides were identified in precipitation samples (wet and dry deposition) from 5 locations in Northern Germany and the island of Heligoland (North Sea). The temporal development of the concentrations as well as deposition rates of three triazine herbicides, atrazine, simazine and terbutylazine, and of the metabolite desethylterbutylazine in total deposition samples from locations close to the source (agriculture) are compared to values obtained from the sampler on the island of Heligoland (marine sampling site). The concentrations ranged from < 3 to 500 ng/L. Deposition rates are presented for the respective sampling intervals as well as on a seasonal basis for all sampling sites Furthermore, gradients for the atmospheric transport or deposition, respectively, are calculated which may represent the dilution effect between source and Heligoland. For terbutylazine this gradient turned out to be 5:1, while for atrazine the value was about 1:1. The annual atmospheric deposition of triazine derivatives in the German Bight (North Sea) is estimated to be 20 μg/m2 which implies an input to the German Bight of about 500 kg triazines per year. This value is compared to riverine input of about 3 000 kg atrazine, 16 000 kg simazine and 2 000 kg terbutylazine per year.

Molecular parity violation via comets

Recent theoretical and experimental investigations referring to the origin of homochirality are reviewed and integrated into the hitherto known state of the art. Attention is directed to an extraterrestrial scenario, which describes the interaction of circularly polarized synchrotron radiation with interstellar organic matter. Following this Bonner-Rubenstein hypothesis, optically active molecules could be transferred to Earth via comets. We plan to identify any enantiomeric enhancement in organic molecules of the cometary matter in situ. The present preliminary experimental study intends to optimize gas-chromatographic conditions for the separation of racemates into their enantiomer constituents on the surface of the comet 46P/Wirtanen. Underivatized racemic pairs of alcohols, diols, and phenyl-substituted amines have been separated with the help of a stationary trifluoroacetyl-cyclodextrin phase. We are still developing a technique that will enable us to detect any enantiomeric enhancement of specific simple organic molecules both in cometary or Martian matter in situ and in meteorites found on Earth.

Pyrolytic methylation assisted enantioseparation of chiral hydroxycarboxylic acids

Abstract Quaternary ammonium salts and dialkylformamide acetals have been demonstrated to be effective reactants for the injector port gas phase derivatization of organic compounds which have insufficient chromatographic properties. A derivatization method is described, in which dimethylformamide dimethylacetal is used as a methylating reagent for hydroxycarboxylic acids in the heated insert zone directly before their gas chromatographic enantioseparation. The results show that the chiral lactic, malic, mandelic, and tartaric acids or mixtures thereof were transformed into their methyl esters very quickly; these esters could easily be resolved into their enantiomers by gas chromatography employing chiral stationary phases. The amount of required samples depends on the analyte and could be limited to a few nanomoles; the entire derivatization procedure could be performed in less than 1 min. We examined the potential reagents systematically to select one of them for application in the COSAC experiment within ESAs ROSETTA mission, where solvent chemistry should be avoided because the transformation of polar organic compounds into derivatives suitable for chromatographic separation has to be performed on the surface of a cometary nucleus under near-zero gravity.

Analysis of chlorinated paraffins in cutting fluids and sealing materials by carbon skeleton reaction gas chromatography

Chlorinated paraffins (CPs) pose a major risk in the environment, due to their wide application, to their persistence, to their carcinogenic potential, and in view of the fact, that they cannot be easily identified. Various commercial cutting fluids and sealing materials were analysed for CPs with carbon skeleton reaction gas chromatography (GC) and flame ionization detection. CPs are simultaneously dechlorinated and hydrogenated to the corresponding alkanes with Pd catalyst material in the GC injector. With this method, the carbon chain length of commercial technical CPs was determined. In six of sixteen sealing materials we found five short and one medium chain length polychlorinated paraffins in percentages of 9-16% (w/w). In five cutting fluids we found predominantly medium to long chain length chloroparaffins with percentages of 2.5-31% (w/w), only one fluid contained short chain CPs.