Sensitivity and resolution optimization in gas chromatography coupled to mass spectrometry analyses of volatile organic compounds present in vacuum environment.

The gaseous phase analyses of volatile organic compounds (VOCs) are an important challenge especially when these organics are formed in high vacuum environments (10-8 mbar) reproducing the environment of astrophysical ices formation and processing. Several analytical techniques have been developed to identify the molecular diversity formed from the processing of these ices. Among them, the coupling of a GC-MS to the vacuum chamber where ices are processed highlighted the interesting chemical diversity of such processed ices. These analyses were possible due to the development of a specific system, the VAHIIA interface that enables the preconcentration of VOCs at low pressure (10-8 mbar) and their transfer at higher pressure to the injection unit of a GC for their subsequent analyses. This system showed sufficient repeatability (13%) and low detection limits (nmol) for simple ices [1], but presents limits when ice mixtures are complex (such as multi-component ices including water, methanol and ammonia). In this contribution, we present the optimization of our previous VAHIIA system by implementing a cryofocusing system in the GC oven and by improving the recovery yield of VOCs from the vacuum chamber to the VAHIIA interface. The cryofocusing provides an improvement of efficiencies leading to higher resolution and signal to noise ratio, while the addition of argon in the vacuum chamber during the VOC recovery allows increasing the amount of molecules recovered by a factor of ∼200. The coupling of both approaches provides an increase of sensitivity of a factor ∼400. At the end, experiments on astrophysical ices are shown demonstrating the interest of such optimizations for VOC analyses.

Development of liquid chromatography high resolution mass spectrometry strategies for the screening of complex organic matter: Application to astrophysical simulated materials.

The present work aims at developing two LC-HRMS setups for the screening of organic matter in astrophysical samples. Their analytical development has been demonstrated on a 100-µg residue coming from the photo-thermo chemical processing of a cometary ice analog produced in laboratory. The first 1D-LC-HRMS setup combines a serially coupled columns configuration with HRMS detection. It has allowed to discriminate among different chemical families (amino acids, sugars, nucleobases and oligopeptides) in only one chromatographic run without neither a priori acid hydrolysis nor chemical derivatisation. The second setup is a dual-LC configuration which connects a series of trapping columns with analytical reverse-phase columns. By coupling on-line these two distinct LC units with a HRMS detection, high mass compounds (350

The Prebiotic C-Terminal Elongation of Peptides Can Be Initiated by N-Carbamoyl Amino Acids.

The formation of peptides upon 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)-promoted activation of N-carbamoylamino acids (CAA), was considered in the scope of our recent works on carbodiimide promoted C-terminus elongation of peptides in a prebiotic context. Thus EDC promoted activation of CAA derivatives of Tyr(Me) or Ala in dilute aqueous medium pH 5.5-6.5 in the presence of excess of AA, resulted in peptide formation by C-terminus activation/elongation. Kinetic results similar to those of EDC-mediated activation of N-acyl-AA lead us to postulate the formation of a 2-amino-5(4H)-oxazolone intermediate by cyclization of the activated CAA, in spite of the absence of epimerization occurred at CAA residues. Thus, in a prebiotic context, CAA may have played a similar role as N-acyl-AA in the initiation of C-terminus peptide elongation.

Development and optimization of an analytical system for volatile organic compound analysis coming from the heating of interstellar/cometary ice analogues.

This contribution presents an original analytical system for studying volatile organic compounds (VOC) coming from the heating and/or irradiation of interstellar/cometary ice analogues (VAHIIA system) through laboratory experiments. The VAHIIA system brings solutions to three analytical constraints regarding chromatography analysis: the low desorption kinetics of VOC (many hours) in the vacuum chamber during laboratory experiments, the low pressure under which they sublime (10(-9) mbar), and the presence of water in ice analogues. The VAHIIA system which we developed, calibrated, and optimized is composed of two units. The first is a preconcentration unit providing the VOC recovery. This unit is based on a cryogenic trapping which allows VOC preconcentration and provides an adequate pressure allowing their subsequent transfer to an injection unit. The latter is a gaseous injection unit allowing the direct injection into the GC-MS of the VOC previously transferred from the preconcentration unit. The feasibility of the online transfer through this interface is demonstrated. Nanomoles of VOC can be detected with the VAHIIA system, and the variability in replicate measurements is lower than 13%. The advantages of the GC-MS in comparison to infrared spectroscopy are pointed out, the GC-MS allowing an unambiguous identification of compounds coming from complex mixtures. Beyond the application to astrophysical subjects, these analytical developments can be used for all systems requiring vacuum/cryogenic environments.

Formation of hydroxyacetonitrile (HOCH2CN) and polyoxymethylene (POM)-derivatives in comets from formaldehyde (CH2O) and hydrogen cyanide (HCN) activated by water.

Studying chemical reactivity is an important way to improve our understanding of the origin of organic matter in astrophysical environments such as molecular clouds, protoplanetary disks, and possibly, as a final destination, in our solar system bodies such as in comets. Laboratory simulations on the reactivity of ice analogs can provide important insights into this complex reactivity. Here, the role of water as a catalytic agent is investigated under the conditions of simulated interstellar and cometary grains in the formation of complex organic molecules: the hydroxyacetonitrile (HOCH2CN) and formaldehyde polymers (polyoxymethylene POM). Using infrared spectroscopy and mass spectrometry, we show that HCN reacts with CH2O only in the presence of H2O, whereas in the absence of H2O, HCN is not sufficiently reactive to promote this reaction. Furthermore, depending on the dilution of CH2O and HCN in the water matrix, 1-cyanopolyoxymethylene polymers can also be formed (H-(O-CH2)n-CN, POM-CN), as confirmed by mass spectrometry using the HC(15)N isotopologue. Moreover, quantum chemical calculations allowed us to suggest mechanistic proposals for these reactions, the first step being the activation of HCN by water forming H3O(+) and CN(-), which subsequently condense on a neighbouring CH2O promoting the formation of (-)OCH2CN. Once (-)OCH2CN is formed, it can either recover a proton by reacting with H3O(+) or condense on CH2O molecules leading to POM-CN structures. Implications of this work for the forthcoming Rosetta mission are also addressed.

Passive sampling: an effective method for monitoring seasonal and spatial variability of dissolved hydrophobic organic contaminants and metals in the Danube river.

Application of passive samplers is demonstrated for assessment of temporal and spatial trends of dissolved polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and priority metals in the middle stretch of the Danube river. Free dissolved concentrations of PAHs, measured using SPMD samplers, ranged from 5 to 72 ng L(-1). Dissolved PCBs in water were very low and they ranged from 5 to 16 pg L(-1). Concentration of mercury, cadmium, lead and nickel, measured using DGT samplers, were relatively constant along the monitored Danube stretch and in the range <0.1, <1-20, 18-74, and 173-544 ng L(-1), respectively. Concentrations of PAHs decreased with increasing temperature, which reflects the seasonality in emissions to water. This has an implication for the design of future monitoring programs aimed at assessment of long term trends. For such analysis time series should be constructed of data from samples collected always in the same season of the year.