Strong Organic Solvents Research Articles

Microfluidic synthesis of atto-liter scale double emulsions toward ultrafine hollow silica spheres with hierarchical pore networks

A facile PDMS-glass hybrid microfluidic device is developed for generating uniform submicrometer-scale double emulsion droplets with unprecedented simplicity and controllability. Compared with planar flow-focusing geometries, our three-dimensional flow-focusing geometry is advantageous for stably producing femto- to atto-liter droplets without the retraction problem of the dispersed phase fluid. In addition, this microfluidic platform can withstand the use of strong organic solvents (e.g. tetrahydrofuran (THF) and toluene) as a dispersed phase without deforming PDMS devices because the dispersed phase containing organic solvents does not directly contact the PDMS wall. In particular, monodisperse double emulsions are generated spontaneously via the internal phase separation of single emulsions driven by the diffusion of a co-solvent (tetrahydrofuran) in microfluidic devices. Finally, we demonstrated that the double emulsions can be used as morphological templates of ultrafine spherical silica capsules with controlled hierarchical pore networks via the evaporation-induced self-assembly (EISA) method. During EISA, triblock copolymers (Pluronic F127) act as a surfactant barrier separating the internal droplet from the continuous oil phase, resulting in the 'inverse' morphology (i.e. hydrophobic polymer-in-water-in-oil emulsions). Depending on the precursor composition and kinetic condition, various structural and morphological features, such as mesoporous hollow silica spheres with a single central core, multi-cores, or a combination of these with robust controllability can be seen. Electron microscopy (SEM, STEM, HR-TEM), small angle X-ray scattering (SAXS), and N(2) adsorption-desorption confirm the well-controlled hierarchical pore structure of the resulting particles.

Solvent‐Free Chemoselective Cyanation of α,α‐Dibromoacetophenones Using Potassium Hexacyanoferrate(II) as an Eco‐Friendly Cyanide Source

AbstractA chemoselective route for the synthesis of 2‐aryl‐3,3‐dibromoacrylonitriles by solvent‐free cyanation of α,α‐dibromoacetophenones by using potassium hexacyanoferrate(II) as an eco‐friendly cyanide source is developed. The merits of this procedure include avoiding the use of a strong toxic cyanide source, a catalyst, and volatile organic solvents and the high yields of the products.

Water-immiscible solvents as diluents in reversed-phase liquid chromatography

It has recently been shown that the use of strong organic solvents as diluent is possible in RPLC, provided that the solvent used as diluent is retained more strongly by the column than the analytes in the sample. In this study, the phenomenon was further studied experimentally using several water-immiscible solvents (ethyl acetate, isopropyl acetate, and methyl isobutyl ketone) and several model analyte compounds. In all cases, analyte peak distortion was minimal provided the analyte eluted earlier than the diluting solvent, in contrast to substantial broadening and distortion when the analyte eluted after the diluting solvent. The potential analytical utility of this approach is discussed, and an example of a practical application is also presented.

A quantitative comparison of the commonly used methods for extracting carotenoids from avian plasma

Interest in animal carotenoids, especially in birds, has exploded in recent years, and so too have the methods employed to investigate the nature and function of these pigments. Perhaps the most easily and commonly performed procedure in this work has been the determination of carotenoid concentration from avian plasma. Over the past 20 years of research on avian carotenoids, numerous methods have been used to extract carotenoids from bird plasma, all of which have differed in several important parameters (e.g., number and types of solvents used, degree of mixing/centrifugation). However, to date, no study has systematically compared these methods to determine if any of them are more effective than others for recovering any or all types of carotenoids present. We undertook such an investigation on plasma samples from two bird species (house finch, Carpodacus mexicanus, and mallard, Anas platyrhynchos) using five of the most commonly employed methods for extracting carotenoids from avian plasma: (1) acetone-only, (2) methanol-only, (3) ethanol-only, (4) ethanol + hexane, and (5) ethanol + tert butyl methyl ether. We also manipulated the amount of time that extracts were centrifuged, which has varied tremendously in previous studies, to evaluate its importance on carotenoid recovery. We found that all methods equally recovered the polar xanthophylls (lutein and zeaxanthin), but that the methanol-only procedure poorly recovered non-polar carotenoids (less β-carotene in both species and less β-cryptoxanthin in house finches) compared to the other methods. These results suggest that the data accumulated to date on xanthophyll plasma carotenoids in birds should be comparable across studies and species despite the different chemical extraction methods used. However, care should be taken to use relatively strong organic solvents for fully recovering non-polar carotenoids. We also found no effect of centrifugation duration (1 vs. 10 min at 10,000 rpm) on carotenoid recoveries, demonstrating that researchers can save considerable time by centrifuging for a much shorter time period than is typically used.

The Aldol Addition and Condensation: The Effect of Conditions on Reaction Pathway

The reaction of a ketone and an aldehyde in aqueous Na2CO2 is described. This experiment is performed in the absence of strong bases or organic solvents and offers the opportunity for students to observe the critical role that reaction temperature and base strength have in determining the product of the base-mediated addition of a ketone to an aldehyde. When the reaction takes place at room temperature, the aldol addition product is produced. But, when the reaction is heated to 50 °C, the aldol condensation product is isolated. Both reactions use the same quantities of reagents. The reaction temperature is the factor that determines which product is formed. When NaOH is used in place of Na2CO2, the aldol condensation product is isolated regardless of temperature.

A Critical Assessment of Studies on the Carcinogenic Potential of Diesel Exhaust

After decades of research involving numerous epidemiologic studies and extensive investigations in laboratory animals, a causal relationship between diesel exhaust (DE) exposure and lung cancer has not been conclusively demonstrated. Epidemiologic studies of the transportation industry (trucking, busing, and railroad) show a small elevation in lung cancer incidence (relative risks [RRs] generally below 1.5), but a dose response for DE is lacking. The studies are also limited by a lack of quantitative concurrent exposure data and inadequate or lack of controls for potential confounders, particularly tobacco smoking. Furthermore, prior to dieselization, similar elevations in lung cancer incidence have been reported for truck drivers, and in-cab diesel particulate matter (DPM) exposures of truck drivers were comparable to ambient highway exposures. Taken together, these findings suggest that an unidentified occupational agent or lifestyle factor might be responsible for the low elevations in lung cancer reported in the transportation studies. In contrast, underground miners, many of whom experience the highest occupational DPM exposures, generally do not show elevations in lung cancer. Laboratory studies must be interpreted with caution with respect to predicting the carcinogenic potential of DE in humans. Tumors observed in rats following lifetime chronic inhalation of very high levels of DPM may be attributed to species-specific overload mechanisms that lack relevance to humans. Increased tumor incidence was not observed in other species (hamsters or mice) exposed to DPM at very high levels or in rats exposed at lower levels (≤2000 μg/m3). Although DPM contains mutagens, mutagenicity studies in which cells were exposed to concentrated extracts of DPM also have limited application to human risk assessment, because such extracts can be obtained from DPM only by using strong organic solvents, agitation, and heat. Most studies have shown that whole DPM itself is not mutagenic because the adsorbed organic compounds are minimally bioavailable in aqueous-based fluids. In the past two decades, dramatic changes in diesel engine technology (e.g., low-sulfur fuel and exhaust after-treatment) have resulted in >99% reduction in DPM and other quantitative and qualitative changes in the chemical and physical characteristics of diesel exhaust. Thus, the current database, which is focused almost entirely on the potential health effects of traditional diesel exhaust (TDE), has only limited utility in assessing the potential health risks of new-technology diesel exhaust (NTDE). To overcome some of the limitations of the historical epidemiologic database on TDE and to gain further insights into the potential health effects of NTDE, new studies are underway and more studies are planned.

Grazing incidence diffraction of cadmium arachidate multilayers at the solid-liquid interface

Abstract Using complementary X-ray reflectivity (XR) and grazing incidence X-ray diffraction (GIXD), we report structural studies of supported thin-organic layers in contact with water and air. Using a monochromatic synchrotron beam to penetrate 10 mm of liquid, we have characterized buried films composed of 12.5 repeating bilayers of arachidic acid (C20H40O2) complexed with cadmium ions (cadmium arachidate, CdAr2). We found that the layered structure of the CdAr2 multilayers do not exhibit rearrangement after exposure to water with negligible water penetration into the inner layers when compared to their dry state. These findings are consistent with the formation of extremely robust CdAr2 multilayers that can withstand multiple rinses in strong organic solvents, acid, and mechanical wear. The second goal was to demonstrate the feasibility of similar experiments to study much thinner single bilayer bio-membranes. These studies are the first successful GIXD experiments of ultra thin-organic film composed of a few layers at the solid-liquid interface.

On-line preconcentration of mercury using an integrated column/gas-liquid separator (PCGLS) and cold vapour atomic absorption spectrometry

A novel flow injection (FI) method for the determination of mercury at ng l−1 levels was developed, using on-line solid phase extraction and cold vapour atomic absorption spectrometry (CVAAS). The pyrrolidine dithiocarbamate mercury complex Hg(PDC)2, is adsorbed and reduced to elemental mercury, and the generated vapour is separated in a newly specifically designed and constructed unified and combined preconcentration column/gas-liquid separator (PCGLS). The lower of the two sections of PCGLS is a preconcentration column packed with polytetrafluoroethylene (PTFE) turnings for the retention of Hg(PDC)2 and subsequent on-column reduction of mercury by SnCl2. Mercury vapour is generated within the column and expelled from the reaction mixture by passing nitrogen through the PCGLS. The upper section of the PCGLS is a headspace for receiving mercury vapour and separating it from humidity residues before entering the absorption cell. The use of strong inorganic acids or volatile organic solvents as eluents is avoided, because the elution step is eliminated. The excellent performance of PTFE as packing material and the compact design of the PCGLS results in higher sensitivity and sampling frequency and to a more functional and simple manifold. An enrichment factor of 32, a detection limit of cL = 6 ng l−1, a sampling frequency of 30 h−1 were obtained at sample flow rate of 11.5 ml min−1, for 60 s preconcentration time. The precision, expressed as relative standard deviation, at 0.6 µg l−1 Hg(II), was sr = 2.1%. The proposed method overcomes the common interferences including those from volatile organic solvents and has been successfully applied to the determination of inorganic mercury in natural waters, and total mercury in urine and mussel samples after digestion.

Synthesis and lyotropic liquid crystalline behaviour of a taper-shaped phosphonic acid amphiphile

A taper-shaped phosphonic acid, 3,4,5-tris(dodecyloxy)phenylmethylphosphonic acid (1), was synthesized; its lyotropic liquid crystalline (LLC) behaviour and its ability simultaneously to order and acid-dope polyaniline were examined. It was found that the ability of 1 to form LLC phases in the presence of several hydrophilic solvents is restricted by strong intermolecular interactions between the phosphonic acid head groups (presumably H-bonding). The amphiphile exhibits poor miscibility with pure water and even with strong H-bonding organic solvents such as DMF. However, it forms a lamellar mesophase in the presence of aqueous acid. Upon deprotonation of the phosphonic acid head group with NaOH, the resulting disodium salt of the amphiphile is able to form a well defined lamellar phase with pure water. The propensity of 1 to form lamellar phases is somewhat unusual since its tapered molecular shape should direct it to form an inverted hexagonal LLC phase. These results suggest that intermolecular head group interactions are more important in determining the overall LLC behaviour of this phosphonic acid amphiphile than are the hydrophobic character and shape of the organic tail system. Compound 1 was also found to be sufficiently acidic to act as an acid dopant for the conjugated polymer polyaniline in the emeraldine base form. LLC acid 1 induces the resulting polymeric salt to form an electrically conductive LLC complex with an extended lamellar microstructure. The bulk conductivity of the resulting nanostructured polyaniline salt was found to be only in the semiconducting regime (10-5 Scm-1), due to an unfavourable polyaniline chain conformation in the LLC complex.

Synthesis and characterization of organosoluble polyimides with trifluoromethyl‐substituted benzene in the side chain

AbstractNew aromatic diamines substituted with a trifluoromethyl group in the side chain, 2,4‐diamino‐3′‐trifluoromethylazobenzene, 2,4‐diamino‐1‐[(4′‐trifluoromethylphenoxy) phenyl] aniline, and 3,5‐diamino‐1‐[(4′‐trifluoromethyl phenoxy) phenyl] benzamide were synthesized and characterized and used to prepare polyimides by a one‐step high‐temperature polycondensation method. Experimental results indicated that the prepared polyimides possess good solubility in strong organic solvents such as N‐methyl‐2‐pyrrolidinone, N,N′‐dimethylformamide, and N,N′‐dimethylacetamide. Homogeneous solutions with solid contents as high as 15–20% can be prepared, which are stable for storing longer than 2 weeks at room temperature. The polyimides exhibited glass‐transition temperatures of 249–292 °C and good thermal stability. The PI‐Ic and PI‐IIIc films prepared by casting the fully imidized polymer solutions showed good transparency with cutoff wavelengths at 320–330 nm. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1572–1582, 2002

Extraction of cloransulam-methyl from soil with subcritical water and supercritical CO 2

Cloransulam-methyl was extracted from soil samples with supercritical CO 2, subcritical water and conventional organic solvents. Supercritical CO 2 was less efficient than conventional organic solvents; polarity modifiers had no impact on extraction efficiency. Extraction with supercritical CO 2 exhibited a strong temperature dependence. Water was as effective as strong organic solvents for the extraction of cloransulam-methyl; however cloransulam-methyl hydrolyzed when extracted at 150°C. Extraction temperature was the most important variable in increasing the efficiency and rate of extraction, while extraction pressure was not a significant variable.

Development of new SPME fibers by sol–gel technology for SPME-HPLC determination of organometals

Solid-phase micro-extraction (SPME), has advantages of simplicity, low cost, ease of use and rapid pre-concentration and extraction compared to other sample preparation techniques. The technique has found limited use in high performance liquid chromatographic applications because of the unavailability of fibers that are stable and durable in strong organic solvents. This study describes the preparation of fibers that are stable in strong organic solvents (xylene and methylene chloride) as well as acidic and basic solutions (pH 0.3 and 13) using the sol–gel process. The hydrolytic stability of these sol–gel-prepared SPME fibers towards organic solvents and high and low pH solutions can be attributed to the fact that the coating is chemically bonded to the surface of the fused silica substrate. These fibers have been subsequently used to extract organo-arsenic, organo-mercury and organo-tin compounds from aqueous solutions followed by separation using HPLC with UV absorbance detection. Under experimental conditions used, detection limits of 80, 412 and 647 μgl −1for triphenylarsine (Ph 3As), diphenylmercury (Ph 2Hg) and trimethylphenyltin (TMPhT), respectively, were obtained after extraction and HPLC separation. While these detection limits were comparable and/or slightly better than those obtained using commercial SPME fibers, the thinner coatings (resulting in faster extraction time) and the hydrolytic stability of the sol–gel fibers, towards strong organic solvents and high and low pH solutions, gave them superior characteristics when compared to commercially available fibers.

Catalyst regeneration via chemical treatment and emission tests at idle speeds

The present paper examines the possibility of chemical treatment of used catalysts for the purpose of improving catalytic efficiency. The proposed method inserts the catalyst in a bath of a strong organic solvent that dissolves oil, soot and fuel residues, cleaning the active surface of the catalyst. The tests were conducted at low (750 r/min) and high (3100 r/min) idle speeds. The experimental results based on CO, HC and catalyst inlet-outlet temperature difference measurements indicate that after treatment the catalytic efficiency improves considerably (>25 per cent) at low idle (750 r/min). The improvement is even higher at high idle (3100 r/min), exceeding 40 per cent. Therefore, there are strong indications that, if car catalysts underwent a similar treatment at regular service intervals, e.g. every 20 000 km, engine emissions could be considerably reduced and catalyst operational life extended.

Technical Report: Organic Residues from Egyptian Blue Anhydrite Duck Flasks and Other Anhydrite Vessels

in museum collections were originally made to hold organic materials, such as foodstuffs, cosmetics, and perfumes. These organic materials can penetrate into the walls of the vessels, so that residues of the original contents may actually survive even when there is no visible remnant of them. By using strong organic solvents, one can at least partially extract residues trapped in the ceramic or stone and then analyze the extracted compounds. An analysis cannot be expected to provide an accurate view of the original contents for many reasons. The solvent will not necessarily extract all types of organic materials, and the analytical technique utilized to identify the organic materials will not necessarily analyze all of the compounds found in the solvent extract. More important, aging results in the destruction of many organic materials and changes the compositions of others. Volatile components of the original contents may have been lost, and some components may also have been lost to the soil in which an object rested for an extended period of time prior to its excavation. Even given these limitations, analysis of the solvent extract provides a glimpse of the original contents.l This article presents analyses of solvent-extracted organic residues from sixteen anhydrite vessels. The extracts were analyzed by gas chromatography/mass spectrometry (GC/MS).2 Published studies of solvent extracts from ceramics

Fast chromatographic separation of (−)-menthyl chloroformate derivatives of some chiral drugs, with special reference to amlodipine, on porous graphitic carbon

Enantiomeric separation of (−)-menthyl chloroformate derivatives of some chiral cardioactive drugs, on porous graphitic carbon (PGC), Hypercarb-S, is described. Capacity and separation factors of derivatives of the calcium channel blockers; amlodipine and UK52.829, the β-blockers; atenolol, sotalol and propranolol, and mexiletine were studied in different chromatographic systems based on dichloromethane. A high content of a carboxylic acid in the mobile phase was found to decrease the retention and positively affect the stereoselectivity of the derivatives. A mobile phase with dichloromethane, acetonitrile and formic acid gave baseline separation of the enantiomers of amlodipine in less than 8 minutes. Results show that acetic acid and formic acid, may be regarded as strong organic solvents in PGC chromatography with nearly the same elution power as dichloromethane.

Petroleum Source Potential of Miocene and Eocene Shales from the Continental Slope of the Northwestern Gulf of Mexico

From 1965 through 1968, 80 core holes were drilled by the M/V Eureka above shallow salt bodies on the continental slope of the northwestern Gulf of Mexico (offshore Texas and Louisiana) in water depths of 660-5280 ft. (An additional 13 deep-water core holes were drilled in the north-central gulf of Mexico.) Approximately 40,000 ft of sediment and small amounts of diapiric salt and/or associated cap rock were penetrated by these 80 Eureka core holes, from which more than 18,000 ft of core subsequently was recovered. Although most core holes penetrated only Pleistocene sediments, allochthonous sequences of older sediments (Pliocene-Upper Cretaceous) emplaced during salt diapirism were penetrated at eight drill sites in the northwestern Gulf of Mexico. We have determined the petroleum source potential of Miocene and Eocene shales from four deep-water Eureka core holes (water depths of 1890-2350 ft) in the northwestern Gulf of Mexico. All of these samples have attained only moderate levels of thermal maturity (VR [approx] 0.4-0.6). Two samples of Miocene shale obtained from the East Break 672 Block are relatively lean (containing only 0.37-0.54 wt.% total organic carbon) and their kerogen is enriched in gas prone or inert macerals. Eocene shales penetrated in the Alaminos Canyonmore » 970 and 971 blocks are slightly richer (0.68-0.95 wt.% total organic carbon), principally because they contain migrated petroleum-aliquots extracted with a strong organic solvent contain only 0.31 0.48 wt.% total organic carbon. The leanest sample is an Eocene shale obtained from the boundary between the Garden Banks 332 and 333 blocks, approximately 18 mi northwest of the deep-water Auger oil and gas discovery. This sample contains only 0.33 wt% total organic carbon, and its kerogen also consists predominantly of gas-prone or inert macerals. We conclude these Tertiary shale samples are not the source of the oil that has been generated in the deepwater realm of the northwestern Gulf of Mexico.« less