Polar Organics Research Articles

Solution preparation of the amorphous molybdenum oxysulfide MoOS 2 and its use for catalysis

Acid condensation of aqueous MoO 2S 2 2− anion yields amorphous MoOS 2 oxysulfide. This compound possesses tubular morphology and when freshly precipitated is soluble in polar organics such as acetone and ethanol. The ensemble of characterizations (IR, UV–visible, EXAFS spectroscopy) suggests that it contains cyclic or short linear oligomers of neutral molybdenum (V) oxysulfide MoOS 2 core. Thermal decomposition of MoOS 2 under inert atmosphere leads to the formation of a mixture of MoO 2 and MoS 2 phases. Promotion of MoOS 2 with cobalt followed by sulfidation leads to highly active HDS catalysts.

Fast determination of evaporation enthalpies of solvents and binary mixtures using a microsilicon chip device with integrated thin film transducers

A silicon chip device with two types of integrated platinum thin film resistors was applied for microcaloric measurements. It was shown that the device is capable of fast characterization of liquid evaporation behaviour and allows the determination of evaporation enthalpies for pure liquids and mixtures. The applicability was demonstrated for a wide range of solvents from nonpolar aliphatic solvents over polar organics to protic solvents (e.g. iso-octane, toluene, acetone, ethanol, methanol and water). The sample volumes were in the range of about 2–5 μL. The determination of transient times, in case of constant power mode, or the power integral over time was used for the fast estimation of binary liquid mixtures. Thermo-resistive measurements of 5 μL droplets of solvent mixtures like methanol/ iso-propanol, ethanol/water, iso-octane/ iso-propanol and iso-octane/1,4-dioxane showed significant changes in temperature characteristics and evaporation enthalpies in dependence on composition. The applied heating power was about 1 W, which corresponds to measurement times between a few seconds and a minute.

Influence of operation parameters on the separation of mixtures by pervaporation and vapor permeation with inorganic membranes. Part 2: Purely organic systems

The performance of commercially available tubular Y-type zeolite membranes was studied for organic separations by vapor permeation. The separation characteristics were determined as function of operating conditions such as concentration, temperature, permeate and feed pressure. The production quality of the tested membranes, in terms of flux and selectivity, was reproducible within a range of 10%. The partial flux of both the preferentially permeating and the retained components generally increase with partial pressure difference in feed and permeate. A constant permeance model may be used to estimate the flux of lower alcohols in mixtures with various non polar organics. Y-type zeolite membranes exhibit permeance values of 2.5 and 1.2 kg / m 2 h bar , respectively for methanol and ethanol and a separation factor over toluene of 100 for methanol and 70 for ethanol, both determined at moderate to high alcohol concentration. There are, however, considerable differences between ideal and mixture selectivities and the error for the flux of the retained component may become large at small concentrations of the preferentially permeating component. The most remarkable abnormality in flux behavior can be observed for a partially Ca-exchanged NaY-Zeolite that shows strongly preferential permeation for methanol at higher methanol concentrations and a marked selectivity in favor of toluene at low methanol concentration. The flux increases with temperature according to an Arrhenius-function, while selectivity does not change significantly. The selectivity can be changed by ion-exchange of the incorporated counter-ions in the zeolite lattice. The separation mechanism is mainly based on preferential adsorption and differences in mobility rather than on size or shape selectivity. With regard to the operation stability of the membranes when separating purely organic systems with the Y-type zeolite, pore blocking, adsorption and coking occurred and reduced the measured flux rates with operation time. The membrane could be partly regenerated by thermal treatment with a nitrogen sweep at 200 °C under vacuum. The installation of a wire mesh demister to reject droplets of heavy boilers in the feed vapor solved the problem.

Comparison of vancomycin-based stationary phases with different chiral selector coverage for enantioselective separation of selected drugs in high-performance liquid chromatography

Two vancomycin-based chiral stationary phases (CSPs) with different coverage of the chiral selector vancomycin (Chirobiotic V and Chirobiotic V2) were compared. β-Blockers and profens, as structurally diverse groups of drugs, were chosen as analytes. Retention and enantioseparation of β-blockers were studied in reversed-phase (RP) and polar-organic (PO) separation modes. Higher retention and better enantioresolution were obtained on the CSP with higher coverage of vancomycin in the both separation modes. Baseline separation of four β-blockers (eight enantiomers) in the PO mode was achieved on the Chirobiotic V2 column within 15 min. The enantioseparation of profens did not bring so excellent and easy to interpret results. Higher retention of profens on the Chirobiotic V2 column was not always accompanied by an improvement of their chiral separation in the RP mode. The polar-organic mode was not suitable for these derivatives at all. The most interesting result was obtained with flobufen; its chiral center is further away from the rigid part of the molecule, which mostly causes difficulties in enantioselective recognition. Nevertheless, the enantiomers of flobufen were shown to be much better (baseline) resolved on the CSP with lower coverage of the chiral selector (Chirobiotic V).

Superheated Water Extraction of Lime Peel: a Comparison with Conventional Methods

A comparative study of superheated water extraction (SWE) with several conventional methods was performed on lime (Citrus aurantifolia, Swing) peel. Some superheated water parameters affecting the extraction were studied, such as temperature, dynamic and static time, and flow rate. At 130°C, a static and dynamic time of 5 and 15 min, and a water flow at 1 mL min−1, the main components of aroma compounds were successfully removed and collected in 2 mL hexane. Separation and identification of the components were carried out by using gas chromatography‐flame ionization detection (GC‐FID) and GC‐MS. The extraction technique was compared with steam or water distillation and organic solvent sonication. With the same amount of the extract, the highest oxygenated compound yield was found for SWE, while the less valuable monoterpene yields were maximized when using dichloromethane sonication. The composition of oxygenated components present in the SWE extracts, namely linalool, neral, terpineol, geranial, and geraniol, were 4.94, 19.13, 13.03, 30.00, and 10.48%, respectively. Compared in terms of the equal amount of internal standard, water distillation gave highest efficiency in removal of oxygenated components; however, the method required a long extraction time, making it less attractive. The proposed technique was also modified by adding 10–30% methanol or ethanol into the water. A high percentage of alcohol dramatically increased the extraction efficiency of monoterpene but slightly for the oxygenated components. The modified superheated water extraction, therefore, is considered to be an alternative technique to obtain high extraction efficiencies of low polar organics and possibly at a lower temperature.

?-Tubulin localization changes from discrete polar organizers to anastral spindles and phragmoplasts in mitosis of Marchantia polymorpha L.

Unlike the astral mitotic spindle that is organized at discrete centriolar centrosomes, the spindle of land plants is typically anastral and its origin has remained obscure. Gamma tubulin (gamma-tubulin), an important component of the centrosome, has been demonstrated at microtubule-nucleating sites in plant cells. Mitotic spindles of certain hepatics are initiated at distinct acentriolar polar organizers (POs) that appear de novo at the onset of mitosis. Data on the relationship of gamma-tubulin to POs and to microtubule arrays throughout the cell cycle were collected from rapidly dividing cells of Marchantia polymorpha (Bryophyta) that were triple-stained for gamma-tubulin, microtubules, and nuclei. POs at opposite ends of the elongated nucleus in early prophase stain brightly for gamma-tubulin and astral microtubules emanating from them initiate the spindle. As the spindle develops, however, the gamma-tubulin becomes dispersed from the highly concentrated spherical form of the POs to more diffusely organized cups at tips of the fusiform nucleus. By the end of prophase, all astral microtubules have disappeared and the gamma-tubulin is located in several minipoles along the now broad polar regions of the spindle. At metaphase, gamma-tubulin extends into the spindle itself. By telophase, the gamma-tubulin has migrated from distal to proximal surfaces of the sister nuclei and extends into the phragmoplast. Upon completion of cytokinesis, gamma-tubulin appears diminished and surrounds the nuclear envelopes. These data show that gamma-tubulin is only briefly concentrated in the PO, migrates in a cell-cycle-specific manner, and is consistently present at all putative sites of microtubule nucleation.

Gamma-Tubulin, microtubule arrays, and quadripolarity during sporogenesis in the hepatic Aneura pinguis (Metzgeriales).

This is the first report on the organization of a quadripolar microtubule system (QMS) in polyplastidic meiosis of a hepatic with polar organizers (POs). Unlike the monoplastidic sporocytes of mosses and hornworts, in which meiotic quadripolarity can be traced to plastid division and migration, sporocytes of Aneura pinguis are polyplastidic and tetrahedrally lobed before the QMS is organized. Whereas the QMS in mosses and hornworts is plastid-based, the QMS of A. pinguis is focused at four POs where gamma tubulin (gamma-tubulin) is concentrated. An aster of microtubules emanates from each PO centered in the four cytoplasmic lobes and the opposing radial microtubules interact to form the QMS that envelops the nucleus. A functionally bipolar spindle is gradually formed as the four poles converge in pairs on either side of opposite cleavage furrows. The resulting spindle remains quadripolar. Although gamma-tubulin is most concentrated in the deeply concave poles straddling cleavage furrows, it also extends into the spindle itself. Telophase groups of chromosomes curve around the polar cleavage furrows and a phragmoplast that originates in the interzonal region guides a cell plate that extends to the equatorial cleavage furrows. Discrete POs are reformed at opposite tips of the elongated dyad nuclei in prophase II and microtubules radiating from them give rise to the spindles of second meiosis. Spindles remain sharply focused and gamma-tubulin extends into distal portions of the spindle. Interzonal phragmoplasts that expand to join with pre-established cleavage furrows mediate cytokinesis resulting in a tetrad of spores. Each young tetrad member has a radial microtubule system emanating from the nucleus.

New copolyimide membranes with high siloxane content designed to remove polar organics from water by pervaporation

The syntheses of oligodimethylsiloxane film forming materials and their organoselective properties for the removal of ethanol and phenol from water by pervaporation are reported. Two series of segmented polydimethylsiloxane-imide (PSI) copolymers were synthesized from α,ω-(bisaminopropyl) dimethylsiloxane oligomers (ODMS) and aromatic dianhydrides (PMDA, 6FDA); synthesized PSI were obtained with a high content of siloxane block, i.e. up to 94 wt.%. To improve the average molecular weight of siloxane copolymers prepared from the longer chain length ODMS, the particular extender 1,3-bis(3-aminopropyl) tetramethyldisolxane (MDMS) was used, giving thus materials with enhanced mechanical properties. Pervaporation (PV) results showed that the PSI led to a selective recovery of the organic compounds from their aqueous mixtures. The structure-properties relationships of these materials are discussed with respect of polydimethylsiloxane-imide microstructures, taking into account especially the dianhydride type and the chain length of the oligomers used. PSI having a high amount of siloxane blocks gave the best PV results and optimum pervaporation performances were obtained with membranes incorporating aromatic fluorinated residues (feed=5 wt.% PhOH: α=22 and J 10μm=2.4 kg/m 2 h/feed=10 wt.% EtOH: α=10.6 and J 10μm=0.56 kg/m 2 h).

Total Petroleum Hydrocarbons in Groundwater—Evaluation of Nondissolved and Nonhydrocarbon Fractions

Total petroleum hydrocarbons (TPH) in groundwater samples are commonly extracted and analyzed for comparison to regulatory standards and for forensic evaluation of the source of spilled petroleum. While this procedure is normally intended to provide information on hydrocarbons dissolved in water, several complicating factors exist. In this study, the significance of reported TPH values is evaluated for a suite of surface water, interstitial, and groundwater samples by comparing analytical data obtained on unfiltered water, filtered water, and water from which nonhydrocarbons were removed by treatment with silica gel. Results indicate that standard measurements of TPH in groundwater not only include dissolved petroleum hydrocarbons, but commonly also include contributions from: (1) hydrocarbons sorbed on particulate matter; (2) droplets or micellular forms of liquid hydrocarbon contamination; (3) biogenic hydrocarbons; (4) contamination by field or laboratory equipment; and (5) dissolved polar organics (nonhydrocarbons), which may be naturally occurring or derived from spilled petroleum products. These factors complicate the regulatory and forensic interpretation of standard TPH data for groundwater samples.

Adsorption Isotherms of Polar and Nonpolar Organic Compounds on MCM-48 at (303.15, 313.15, and 323.15) K

Adsorption equilibria of four nonpolar molecules (benzene, toluene, hexane, and cyclohexane) and two polar molecules (methanol and acetone) on mesoporous silicate MCM-48 were measured at (303.15, 313.15, and 323.15) K using a gravimetric technique. It was found that MCM-48 has a higher affinity to polar organic compounds than to nonpolar organics. A hybrid isotherm model composed of Langmuir isotherm and Sips equations was applied to fit the adsorption equilibrium data of nonpolar organics including surface adsorption and capillary condensation, while inhomogeneous Dubinin−Astakov (DA) isotherm was used to correlate those of polar organics. The proposed isotherms correlated the measured adsorption data well over the whole range at these experimental conditions.

Demonstration of simultaneous anion-exchange and reversed-phase behavior on a strong anion-exchange column

We demonstrate in this report that a conventional silica-based strong anion-exchange column can exhibit reversed-phase chromatographic behavior simultaneously with ion-exchange in a methanol–aqueous phthalate mobile phase. Reversed-phase behavior is shown for PAHs in relatively high methanol-content mobile phases, while polar organics exhibit reversed-phase behavior in 0–10% (v/v) methanol–water eluents. At low concentrations (0–10% v/v) methanol has little or no effect on anion retention, while the anions exhibit only slight increases in retention in 60–80% (v/v) methanol at near-neutral pH values. Likewise, pH changes used to manipulate anion retention have essentially no effect on PAH retention, and cause only small decreases in retention for most of the polar organics studied. Little or no pH-effect was seen on a phenyl column (no exchange group) or with acetate mobile phase. It is shown that manipulation of pH and methanol content allows the grouping of neutral organic analytes early in a chromatogram, followed by the anions, with no class overlap. Several example chromatograms are given, including that of a red wine sample. Column efficiency was good for anions but only modest for organics.

γ-Tubulin in Bryophytes

Summary: γ-Tubulin is a protein associated with microtubule organizing centers(MTOCs)such as centrosomes in animal cells. Although seed plants have γ-tubulin, they do not have discrete MTOCs comparable to centrosomes, and organization of the multiple microtubule arrays in plants has been enigmatic. Because basal land plants have an exceptional variety of unique morphologically discrete MTOCs(e. g. centrosome, polar organizer, plastid-based quadripolar microtubule system), microtubule systems in basal land plants may hold clues to evolutionary changes in γ-tubulin localization and function in evolution of acentriolar spindles in plants. In the present study, we isolated and characterized a genomic clone encoding γ-tubulin of a liverwort(Bryophyta)and verified the localization of γ-tubulin on several types of discrete MTOCs in bryophytes using the G9 anti-γ-tubulin antibody that recognized ca. 55kDa peptide of bryophytes. We also describe changes in the localization of γ-tubulin closely correlated with the MTOC cycle in meiosis of the liverwort, Dumortiera hirsuta. γ-Tubulin is detectable on the surface of isolated plastids and nuclei and microtubules can be repolymerized from the isolated plastids. γ-Tubulin localization on plastid and nuclear surfaces are not affected by destruction of microtubules by oryzalin. From these results, we conclude that γ-tubulin is a highly conserved protein associated with microtubule nucleation in basal land plants, and it has cell cycle dependent manner essential for the orderly succession of microtubule arrays.

Photolysis and Biodegradation of Selected Resin Acids in River Saale Water, Germany

The River Saale is the Elbe's major tributary flowing through the state of Thuringia, Germany and receives organics inputs from several industrial facilities including pulp and paper mills. Resin acids constitute a major class of polar organics and environmental toxins derived primarily from pulp and paper processing of softwoods. Since wastewater treatment methods at pulp and paper mills are not always capable of removing the persistent resin acids prior to effluent discharge, alternative or complementary degradation methods may be required. Here, the facile photodegradation of four resin acids—abietic, dehydroabietic, isopimaric, and pimaric—was observed with pseudo-first-order kinetics when exposed to broad band and UV254-radiation. Further experimentation in rotating annular biofilm reactors with UV-exposed and unexposed River Saale water spiked with abietic and dehydroabietic acids indicated that photolysis is an effective pretreatment method for resin acid biodegradation. The bacterial toxicity of the aqueous resin acids solutions as measured with Microtox luminescence assays decreased with exposure time. Consequently, photo- and biodegradation of the resin acids did not generate any notable amounts of toxic intermediates and/or the intermediates formed were further degraded into compounds of lower toxicity than the parents. With tandem photo- and biological treatment at pulp and paper mills, as well as in-situ degradation by solar radiation and natural biofilms within the River Saale, resin acid inputs can be reduced in both concentration and toxicity to near undetectable levels with little or no ecological significance.

Water-soluble hydroxylated organic compounds in German and Finnish aerosols

Total suspended particulate matter was collected in a German anthropogenically influenced agricultural area and in a Finnish forest. The occurrence of water-soluble compounds leftover by a traditional dichloromethane (DCM)-extraction technique was investigated using an additional water-extraction and analyzing the corresponding trimethylsilyl derivatives by GC-MS. The organic carbon content of the samples and extracts was also measured. The additional extraction with water recovered more than 20% of total organic carbon, which is comparable to the 31% extracted with DCM. The fraction of water-extractable organic carbon that eluted was <10%, but the employed GC-MS approach proved to be useful in the identification and quantification of polar water-soluble organics containing hydroxyl groups. Concentrations and size distributions of polyhydroxymono- and dicarboxylic acids, polyols, and sugars were obtained. The German meadow presented the highest levels of sugars and acidic compounds, whilst polyols were the most abundant class in the Finnish forest. The major compounds of these classes were malic acid, mannitol, arabitol, glucose and sucrose. Levoglucosan was also detected in the water-extract. Acidic compounds occurred mainly in fine particles. Polyols and most sugars presented size distributions with variable fine or coarse maximum. Possible primary and secondary sources of polyhydroxylated compounds are discussed.

Kinetics and Mechanism of Carbon Incorporation in Ultrathin Silicon-Based Dielectric Films

The effect of various processing conditions on the extent of adsorption of organics and incorporation of carbon in during thermal oxidation is investigated. The key parameters studied are preoxidation cleaning, temperature-ramp rate and ambient, gas-phase impurity concentration, and the presence of moisture. A novel method based on the catalytic oxidation of organics is developed to monitor and characterize the outgassing of organics. Results show that SC1-last surfaces adsorb more polar organics than do HF-last surfaces; this results in a higher amount of carbon incorporation. HF-last surfaces, however, retain a larger fraction of the adsorbed organics. Addition of oxygen to the temperature-ramp ambient reduces the extent of carbon incorporation. The kinetics and mechanisms of carbon incorporation in substrates are investigated. A reaction model based on the competitive processes of desorption, readsorption, decomposition, oxidation, and chemisorption of the adsorbed organics is developed. This model provides a better understanding of one of the key aspects of defect formation in silicon-based dielectric thin films. © 2002 The Electrochemical Society. All rights reserved.

Interaction of Asphalt Films with Aggregate Surfaces in the Presence of Water

ABSTRACT Experiments were conducted to investigate the effects of water on mixtures of neat asphalts with two aggregates. In these experiments, samples of mixtures were contacted with warm water for varying lengths of time. When the samples were removed from water, they were dried and then were contacted with n-heptane. This relatively inert solvent dissolves maltenes, precipitates asphaltenes, and should not disturb polar organic molecules of asphalts adsorbed on aggregate surfaces during water soaking. The polar organics then were recovered using a polar solvent and were weighed and studied by infrared spectrometry. The polar organics recovered were adsorbed from neat asphalts and not solutions of asphalts as in other studies. Measurements of the pH of waters in contact with the mixtures indicate that water rapidly penetrates to asphalt-aggregate interfaces in most of the systems studied. In some systems, amounts of polar organics recovered did not change with soak time. In others, amounts of polar organics increased as a result of water soaking, particularly a combination of a waxy asphalt with granite. The infrared results showed that some carbonyl compounds and 2-quinolones are readily displaced from aggregate surfaces by water, as was found in the solvent studies. Sulfoxide groups do not appear to be as labile. Each asphalt-aggregate combination appears to exhibit a characteristic response to water, as is observed in pavements.

Toxicity of sediments from around a North Sea oil platform: are metals or hydrocarbons responsible for ecological impacts?

Discharges of contaminated drill cuttings have caused appreciable ecological change of the benthos adjacent to many oil and gas platforms in the North Sea. Many platforms have large piles of cuttings lying beneath them and these probably present the greatest potential hazard to the environment during platform decommissioning and removal. There is, however, a lack of consensus on which aspects of drill cuttings are responsible for the adverse ecological effects. This hinders risk assessment of management options. Here we report data on the toxicity of sediments from around the North West Hutton platform to the amphipod Corophium volutator, the polychaete Arenicola marina and the Microtox® acute test system. Sediment was acutely toxic to Corophium out as far as 600 m from the platform. Sediment from 100 m from the platform remained acutely toxic to Corophium when 3% contaminated sediment was mixed with clean sediment. A 10% dilution of this sediment also inhibited Arenicola feeding almost completely. Sediment elutriates did not inhibit Microtox light output, but organics extracted by dichloromethane were very toxic. Fifteen minute EC 50 values were as low as 0.25 mg ml −1 and were strongly correlated with hydrocarbon concentrations. Metal concentrations in whole sediments were correlated with their toxicity to Corophium but the relationship was much weaker when data on dilutions were included. Except at sites immediately adjacent to the platform, metal concentrations were well below ERL values from the literature, so were too low to explain sediment toxicity. Toxicity of sediments to Corophium was closely correlated with their hydrocarbon content, even when tests on dilutions were included in the analysis. We conclude that hydrocarbons are the most significant cause of toxicity in these sediments contaminated with oil based drill cuttings and that polar organics, sulphide, ammonia and other water soluble substances are of much lower significance. Applying OSPAR guidelines to our data on the toxicity of cuttings pile material to Corophium data would give a maximum allowable concentration of 0.03% in clean sediments. The Microtox data indicate that sediments from deeper in the pile would require an even greater dilution than this.

Nanocrystalline metal oxides as unique chemical reagents/sorbents.

A new family of porous inorganic solids based on nanocrystalline metal oxides is discussed. These materials, made up of 4-7 nm MgO, CaO, Al2O3, ZnO, and others, exhibit unparalleled destructive adsorption properties for acid gases, polar organics, and even chemical/biological warfare agents. These unique sorption properties are due to nanocrystal shape, polar surfaces, and high surface areas. Free-flowing powders or consolidated pellets are effective, and pore structure can be controlled by consolidation pressures. Chemical properties can be adjusted by choice of metal oxide as well as by incorporating other oxides as monolayer films.

Organophilicity of MCM-41 adsorbents studied by adsorption and temperature-programmed desorption

In this paper, the organophilic property of MCM-41 was studied and compared with hydrophobic silicalite-1 using adsorption and temperature-programmed desorption (TPD) methods. The surface heterogeneity of MCM-41 was evaluated in terms of activation energy for desorption ( E d) and isosteric heat of adsorption ( q st) . Results show that MCM-41 has a higher affinity to polar organic compounds than to non-polar organics while silicalite-1 has a higher affinity to non-polar organic compounds than to polar organics. This organophilic behaviour of MCM-41 is attributed to its surface heterogeneity.

A preparation technique for analysis of explosives in plant tissues

A preparation technique for analysis of explosives compounds in plant tissue has been developed. The technique utilizes acetone extraction followed by ultrafiltration clean up. Ultrafiltration removes the large quantities of chlorophyll and polar organics that interfere with UV/Vis detection used in high‐performance liquid chromatography. The procedure was tested with 14 explosives‐related compounds spiked into reed canary grass extracts and method detection limits (MDLs) were calculated. In addition, the overall extraction efficiency for RDX in parrot feather and reed canary grass tissues was determined using 14C labeled compound. Scientists may find the technique useful for plant analysis at waste sites and for phytoremediation research.