Dome C ultracarbonaceous Antarctic micrometeorites

Context. UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs) represent a small fraction of interplanetary dust particles reaching the Earth’s surface and contain large amounts of an organic component not found elsewhere. They are most probably sampling a contribution from the outer regions of the solar system to the local interplanetary dust particle (IDP) flux. Aims. We characterize UCAMMs composition focusing on the organic matter, and compare the results to the insoluble organic matter (IOM) from primitive meteorites, IDPs, and the Earth. Methods. We acquired synchrotron infrared microspectroscopy (μFTIR) and μRaman spectra of eight UCAMMs from the Concordia/CSNSM collection, as well as N/C atomic ratios determined with an electron microprobe. Results. The spectra are dominated by an organic component with a low aliphatic CH versus aromatic C=C ratio, and a higher nitrogen fraction and lower oxygen fraction compared to carbonaceous chondrites and IDPs. The UCAMMs carbonyl absorption band is in agreement with a ketone or aldehyde functional group. Some of the IR and Raman spectra show a C≡N band corresponding to a nitrile. The absorption band profile from 1400 to 1100 cm-1 is compatible with the presence of C-N bondings in the carbonaceous network, and is spectrally different from that reported in meteorite IOM. We confirm that the silicate-to-carbon content in UCAMMs is well below that reported in IDPs and meteorites. Together with the high nitrogen abundance relative to carbon building the organic matter matrix, the most likely scenario for the formation of UCAMMs occurs via physicochemical mechanisms taking place in a cold nitrogen rich environment, like the surface of icy parent bodies in the outer solar system. The composition of UCAMMs provides an additional hint of the presence of a heliocentric positive gradient in the C/Si and N/C abundance ratios in the solar system protoplanetary disc evolution.

Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

Within the framework of The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS), this work explores the surface processes and chemistry relating to core/mantle interstellar and cometary grain structures and their influence on the nature of these fascinating particles. It appears that a realistic consideration of the nature and chemical reactivity of interstellar grain surfaces could self-consistently and within a coherent framework explain: the anomalous oxygen depletion, the nature of the CO dark gas, the formation of ‘polar ice’ mantles, the red wing on the 3 μm water ice band, the basis for the O-rich chemistry observed in hot cores, the origin of organic nano-globules and the 3.2 μm ‘carbonyl’ absorption band observed in comet reflectance spectra. It is proposed that the reaction of gas phase species with carbonaceous a-C(:H) grain surfaces in the interstellar medium, in particular the incorporation of atomic oxygen into grain surfaces in epoxide functional groups, is the key to explaining these observations. Thus, the chemistry of cosmic dust is much more intimately related with that of the interstellar gas than has previously been considered. The current models for interstellar gas and dust chemistry will therefore most likely need to be fundamentally modified to include these new grain surface processes.

Photodegradation in Ballistic Laminates: Spectroscopy and Lifetime Extension*

Polycarbonate (PC), a critical component in ballistic laminates (BLs), is known to degrade upon exposure to ultraviolet (UV) light. For the purpose of reducing the photodegradation, a UV blocking chemical has been added to the adhesives used to join the layers of the BL. This report describes the development of a spectroscopic method for monitoring surface photodegradation of PC and the method's use in demonstrating the effectiveness of the UV blocker. Reports in the literature demonstrate that photodegradation in thin PC films may be detected by transmission infrared (IR) spectroscopy. The present work extends this approach to thick films, where small surface changes are detected by reflectance IR spectroscopy. We show that UV photodegradation of the PC surface produces a characteristic shift in the carbonyl absorption band at about 1775 cm−1. This shift is consistently observed in PC samples that have been subjected to direct artificial exposure and in PC samples that have been subjected through the outboard layers of the BL to both natural and artificial exposure. When a UV blocker is incorporated into the adhesive layers of the laminate, no peak shift is observed in the carbonyl band after the equivalent of 10 years of exposure.

Fourier Transform Infrared Spectroscopic Determination of Fenvalerate in Emulsifiable Concentrate Formulation

Fenvalerate [(RS)-α-cyano-3-phenoxybenzyl-(RS)-2-(4-chlorophenyl)-3-methylbutyrate] is extracted from formulation with acetone. The extract is subjected to preparative thin-layer chromatography, and the fenvalerate zone is scraped from the developed plate. Fenvalerate is then eluted from the adsorbent with chloroform and determined by Fourier transform infrared spectroscopy by measuring the carbonyl absorption band at about 1755 cm−1. Recoveries from laboratory-prepared and commercial formulations were 93–99%. The validity of the method was further confirmed by comparing results with those obtained by liquid chromatography.

Examinations of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds. Part V

MI/FT-IR spectral data have been collected on selected types of organic compounds containing the carbonyl group. By the varying of the ratio of the matrix gas to the compound ( M/E) as well as the matrix gas (Ar vs. Xe), the observed splitting of the carbonyl absorption band was attributed to both conformer isolation and aggregation in the matrix. The splitting of the carbonyl group of methyl acetate was attributed to aggregation, while conformer isolation was found to exist for phenyl acetate and trimethylacetaldehyde. The magnitude of the splittings found in this study, 3–30 cm−1, is within the range of values found for other organic compounds. Band splitting was shown by (1) compounds that are linear and contain ≤5 carbons or (2) compounds that are branched and contain <5 carbons. Compounds having >5 carbons displayed only band broadening. Varying M/E ratios has been found to be a reasonable method by which to distinguish between conformer and aggregation. These data confirm the influence of sample phase and indicate that extreme care must be taken in the use of MI/FT-IR spectra as physical probes for structure determination.

Hydrolysis of Atrazine on Soil Colloids

Infrared spectroscopy was used to study the hydrolysis of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] upon interaction with homoionic soil colloids. Montmorillonite, an allophanic soil clay, and a montmorillonitic Coker soil clay were saturated with H+, Al3+, Cu2+, and Ca2+and treated with atrazine and hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Hydrolysis of atrazine was evaluated by the presence of a strong hydroxyatrazine carbonyl absorption band at 1745 cm-1. The H+- and Al3+-saturated montmorillonite and montmorillonitic Coker soil clay promoted atrazine hydrolysis while Ca2+- or Cu2+-saturated montmorillonite did not. A small degree of atrazine hydrolysis was detected in the Cu2+-Coker soil clay. Dehydration of Ca2+- or Cu2+-Coker soil clay after equilibration with atrazine increased the hydrolysis of atrazine. The allophanic soil clay did not catalyze the hydrolysis of atrazine when the exchange complex was saturated with H+, Al3+, Ca2+, or Cu2+. Moreover, Al3+-allophane was not sufficiently acidic to protonate hydroxyatrazine. Thus, a major difference exists between soil allophanic colloids, montmorillonitic soil clays, and montmorillonite as catalysts in the protonation and hydrolysis of atrazine.

Infrared Spectrophotometric Analysis of Aldicarb Formulations

The infrared method described for the assay of aldicarb formulations measures the carbamate carbonyl absorption band at 5.75 μm after extraction with methylene chloride in a Soxhlet extractor. An average recovery of 100.2% was obtained on laboratory-prepared simulated formulations. The standard deviation on repeatability studies on 2 formulations was ±0.2% at the 10% level. The coefficient of variation was ±2%.