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Isopropanol
Selected AbstractsAmmonium perfluorooctanoate as a volatile surfactant for the analysis of N -methylcarbamates by MEKC-ESI-MSELECTROPHORESIS, Issue 22 2006Geert Van Biesen Abstract Ammonium perfluorooctanoate (APFOA) was investigated as an MS-friendly surfactant for the analysis of a mixture of ten N -methylcarbamates with MEKC-ESI-MS. Because of the relatively low boiling point of perfluorooctanoic acid (,190°C), APFOA can be introduced into a mass spectrometer without the adverse effects of less volatile surfactants such as SDS. With a BGE consisting of 50,mM APFOA/isopropanol (IPA) 98:2 and with 30,kV applied, a very fast separation (,6,min) was possible with only one pair of analytes comigrating. Using an experimental design with four factors (voltage, nebulizer pressure, concentration of APFOA, and concentration of IPA) we were able to resolve all analytes in just over 11,min. Sheath liquid composition and flow rate, drying gas temperature and flow rate, and fragmentor voltage were then optimized for maximum signal intensity and S/N. It was found that the faster method gave better S/N because of narrower peak widths, and detection limits in SIM mode were between 0.01 (aldicarb) and 0.08,mg/L (methomyl). Calibration curves were prepared with standards of 0.50, 1.00, and 2.00,mg/L for the analysis of samples obtained after SPE of tap water spiked with the ten N -methylcarbamates at a level of 10,µg/L. All analytes showed very good recoveries (>86%), except for the most polar analyte aldicarb sulfone (recovery of 73%), testifying for the potential use of APFOA for this kind of analyses. [source] Optimization of Isopropanol and Ammonium Sulfate Precipitation Steps in the Purification of Plasmid DNABIOTECHNOLOGY PROGRESS, Issue 4 2006S. S. Freitas Large-scale processes used to manufacture grams of plasmid DNA (pDNA) should be cGMP compliant, economically feasible, and environmentally friendly. Alcohol and salt precipitation techniques are frequently used in plasmid DNA (pDNA) downstream processing, as concentration and prepurification steps, respectively. This work describes a study of a standard 2-propanol (IsopOH; 0.7 v/v) and ammonium sulfate (AS; 2.5 M) precipitation. When inserted in a full process, this tandem precipitation scheme represents a high economic and environmental impact due to the large amounts of the two precipitant agents and their environmental relevance. Thus, major goals of the study were the minimization of precipitants and the selection of the best operating conditions for high pDNA recovery and purity. The pDNA concentration in the starting Escherichia coli alkaline lysate strongly affected the efficiency of IsopOH precipitation as a concentration step. The results showed that although an IsopOH concentration of at least 0.6 (v/v) was required to maximize recovery when using lysates with less than 80 ,g pDNA/mL, concentrations as low as 0.4 v/v could be used with more concentrated lysates (170 ,g pDNA/mL). Following resuspension of pDNA pellets generated by 0.6 v/v IsopOH, precipitation at 4 °C with 2.4 M AS consistently resulted in recoveries higher than 80% and in removal of more than 90% of the impurities (essentially RNA). An experimental design further indicated that AS concentrations could be reduced down to 2.0 M, resulting in an acceptable purity (21,23%) without compromising recovery (84,86%). Plasmid recovery and purity after the sequential IsopOH/AS precipitation could be further improved by increasing the concentration factor (CF) upon IsopOH precipitation from 2 up to 25. Under these conditions, IsopOH and AS concentrations of 0.60 v/v and 1.6 M resulted in high recovery (,100%) and purity (32%). In conclusion, it is possible to reduce substantially the mass of precipitation agents used without affecting recovery, if a small concession is made regarding purity. This directly translates into an improvement of the process economics and in a reduction of the environmental impact of the process. [source] Vapor Condensation Heat Transfer in a Thermoplate Heat ExchangerCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2007J. Mitrovic Abstract The heat transfer and pressure drop in a thermoplate heat exchanger operating as a condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, the single phase forced convection has been studied using distilled water and Marlotherm oil in the thermoplate and correlations developed for the Nusselt number and the friction factor. For the condensation experiments, an apparatus has been constructed comprising two identical condensers composed of the same thermoplate type as employed in the single phase experiments. Isopropanol is used as a test fluid at pressures below atmospheric pressure. The heat transfer resistances in the condensation experiments are separated and expressions for the condensation heat transfer and pressure drop are developed with the aid of the results obtained in the single phase studies. [source] ChemInform Abstract: Symmetric Esters by Tischtschenko Reaction of Aldehydes Catalyzed by Bi- and Tridentate Catalysts Derived from Catechol or Gallol, Trimethylaluminum and Isopropanol.CHEMINFORM, Issue 15 2002Ilkka Simpura Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Quantification of arecoline (areca nut alkaloid) in neonatal biological matrices by high-performance liquid chromatography/electrospray quadrupole mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2003Simona Pichini A high-performance liquid chromatography (HPLC) method with mass spectrometric detection is described for determination of arecoline in newborn meconium, urine and cord serum, using pilocarpine as internal standard. The analytes were extracted from neonatal biological matrices with chloroform/isopropanol (95:5, v/v) at alkaline pH. Extracts were analyzed by HPLC coupled to an electrospray (ESI) interface and a quadrupole mass spectrometer. Chromatography was performed on a C8 reversed-phase column using 10 mM ammonium acetate (pH 4.3)/acetonitrile (90:10, v/v) as mobile phase. The mass spectrometer was operated in selected ion monitoring mode. The method was validated over the concentration range 0.005,1.00,,g/g meconium, 0.004,1.00,,g/mL cord serum and 0.001,1.00,,g/mL urine. Mean recoveries ranged between 86.5 and 90.7% for arecoline in the different biological matrices, with precision always better than 10%. The quantification limits of arecoline were 0.005,,g/g meconium, 0.004,,g/mL cord serum, and 0.001,,g/mL urine. The method was applied to the analysis of neonatal biological matrices to assess eventual fetal exposition to arecoline. Two newborns from Asian mothers who declared areca nut consumption presented arecoline in meconium with concentrations in the range 0.006,0.008,,g/g; also the urine from one neonate tested positive for the drug. Copyright © 2003 John Wiley & Sons, Ltd. [source] Development of fluridil, a topical suppressor of the androgen receptor in androgenetic alopeciaDRUG DEVELOPMENT RESEARCH, Issue 3 2003Allen L Seligson Abstract Nonsteroidal antiandrogens (AA) cannot be topically used for androgenetic alopecia (AGA) because of systemic resorption. A new class of androgen receptor (AR) suppressors designed for safe topical treatment of AGA was synthesized from (3-amino-2-hydroxy-2-methyl- N -(4-nitro-3-trifluoromethyl)phenyl) propanamide (BP-34), to contain perfluoroalkyl moieties. The trifluoromethyl derivative (fluridil) at 10 ,M decreased expression of the AR in LNCaP human cells by 95%, its serum half-life was 6 h; it decomposes hydrolytically to BP-34 and trifluoroacetic acid. Acute intraperitoneal maximum tolerated dose (MTD) of fluridil in mice is 270,300 mg/kg/d and the subacute MTD is 450 mg/kg/d. The oral LD50 in mice was 2,872 mg/kg in males, 2,232 mg/kg in females, and >2,500 mg/kg in rats. Fluridil solution in isopropanol was not cutaneously absorbed in rabbits, did not sensitize or show any phototoxic or photoallergic effects on guinea pig skin, and demonstrated no skin irritation potential in rabbits and humans. Fluridil solid induced only slight and reversible eye irritancy in rabbits and displayed no cytotoxicity to rabbit corneal fibroblasts in vitro. Fluridil demonstrated no significant mutagenicity potential by Ames method. In a double-blind study, 43 males with AGA, Norwood grade II to Va, used topical 2% fluridil in isopropanol or the vehicle daily for 12 months. Anagens (growing hairs) increased in the fluridil group from 76% to 89%. All hematological and biochemistry values remained within normal range, including testosterone, which varied but seasonally. No fluridil or its decomposition product (BP-34) was detected in serum. No adverse side effects were reported. Drug Dev. Res. 59:292,306, 2003. © 2003 Wiley-Liss, Inc. [source] Enhancement of Anodic Response for DMSO at Ruthenium Oxide Film Electrodes as a Result of Doping with Iron(III)ELECTROANALYSIS, Issue 2 2003Brett Abstract The oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO2) is representative of numerous anodic oxygen-transfer reactions of organosulfur compounds that suffer from slow kinetics at noble metal electrodes. Anodic voltammetric data for DMSO are examined at various RuO2 -film electrodes prepared by thermal deposition on titanium substrates. The response for DMSO is slightly larger at RuO2 films prepared in a flame as compared with films prepared in a furnace; however, temperature is more easily controlled in the furnace. Doping of the RuO2 films with Fe(III) further improves the sensitivity of anodic response for DMSO. Optimal response is obtained at an Fe(III)-doped RuO2 -film electrode prepared using a deposition solution of 50,mM RuCl3 and 10,mM FeCl3 in a 1,:,1 mixture of isopropanol and 12,M HCl at an annealing temperature of 450,°C. The Levich plot (i vs. ,1/2) and Koutecky-Levich plot (1/i vs. 1/,1/2) of amperometric data for the oxidation of DMSO at an Fe(III)-doped RuO2 -film electrode configured as a rotated disk are consistent with an anodic response controlled by mass-transport processes at low rotational velocities. Flow injection data demonstrate that Fe(III)-doped RuO2 -film electrodes exhibit detection capability for methionine and cysteine in addition to DMSO. Detection limits for 100-,L injections of the three compounds are ca. 3.2×10,4,mM, i.e., ca. 32,pmol. [source] Application of polymeric surfactants in micellar electrokinetic chromatography-electrospray ionization mass spectrometry of benzodiazepines and benzoxazocine chiral drugsELECTROPHORESIS, Issue 5-6 2006Jingguo Hou Abstract Chiral micellar EKC (CMEKC) coupled to ESI-MS using polymeric surfactants as pseudostationary phases is investigated for simultaneous enantioseparation of two benzodiazepines, (±)-oxazepam ((±)-OXA) and (±)-lorazepam ((±)-LOR), and one benzoxazocine, (±)-nefopam ((±)-NEF). First, enantioselectivity and electrospray sensitivity of six chiral polymeric surfactants for all three chiral compounds are compared. Second, using poly(sodium N -undecenoyl- L -leucinate) as pseudostationary phase, the organic modifiers (methanol (MeOH), isopropanol, and ACN) are added into the running buffer to further improve chiral resolution (RS). Next, a CMEKC-ESI-MS method for the simultaneous enantioseparation of two benzodiazepines is further developed by using a dipeptide polymeric surfactant, poly(sodium N -undecenoxy carbonyl- L,L -leucyl-valinate) (poly- L,L -SUCLV). The CMEKC conditions including nebulizer pressure, capillary length, ammonium acetate concentration, pH, poly- L,L -SUCLV concentration, and capillary temperature were optimized to achieve maximum chiral RS and highest sensitivity of MS detection. The spray chamber parameters (drying gas temperature and drying gas flow rate) as well as sheath liquid conditions (MeOH content, pH, flow rate, and ionic strength) were found to significantly influence MS S/N of both (±)-OXA and (±)-LOR. Finally, a comparative study between simultaneous UV and MS detection showed high plate numbers, better chiral RS, and enhanced detectability with CMEKC-MS. However, speed of analysis was faster using CMEKC-UV. [source] Influence of methanol on the enantioresolution of antihistamines with carboxymethyl-,-cyclodextrin in capillary electrophoresisELECTROPHORESIS, Issue 16 2004Ann Van Eeckhaut Abstract According to the model of Wren and Rowe, the separation between two enantiomers in capillary electrophoresis (CE) decreases if an organic modifier is added to the run buffer containing a neutral cyclodextrin (CD) in a concentration below its optimal value in a solvent-free system. In previous work, however, it was observed that the addition of methanol to the background electrolyte (BGE) containing not charged carboxymethyl-,-CD in a concentration below its optimal value, increased the enantioresolution of dimetindene maleate. The enantioresolution decreased when other organic modifiers (ethanol, isopropanol or acetonitrile) were added and/or when other neutral (,-CD, hydroxypropyl-,-CD) or chargeable (carboxyethyl-,- and succinyl-,-CD) CDs were used. In this CE study further attempts are made to elucidate the observed phenomena through investigating other basic drugs. The effect of organic modifier and CD concentration on the enantioseparation was studied by means of central composite designs. It is shown that obtaining this increase in enantioresolution depends upon the type of CD, the type of organic modifier, and the structure of the analytes. It was also observed that small differences in the structure of the analytes or the CD could have an influence on the enantioresolution. The addition of methanol also resulted in different effects on the resolution of closely related analytes. [source] Utilization of tannery solid waste for protease production by Synergistes sp. in solid-state fermentation and partial protease characterizationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 1 2009Arumugam Ganesh Kumar Abstract Synergistes sp. DQ560074 produced a protease in submerged fermentation (SmF) at 400,420,U/mL and in solid-state fermentation (SSF) at 745,755,U/g. The protease, which belongs to the aspartic protease class, was active over a wide range of pH (5,7) and at high temperatures (25,45°C). The protease is stable and active in various polar protic solvents (50%,v/v) like ethanol, isopropanol, n,butanol, in polar aprotic solvents (50%,v/v) like acetonitrile, and in non-polar solvents (50%,v/v) such as ethylacetate and toluene, but not in hydrophilic organic solvents (methyl alcohol and acetone). As far as we know, this is the first contribution to the production of a mesophilic protease with solvent stability in SSF using a proteinaceous solid waste. [source] Separation and aquatic toxicity of enantiomers of the pyrethroid insecticide lambda-cyhalothrin,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2008Chao Xu Abstract Chiral pollutants are receiving growing environmental concern due to differential biological activities of their enantio-mers. In the present study, enantiomeric separation of the pyrethroid insecticide lambda-cyhalothrin (LCT) was investigated by high-performance liquid chromatography (HPLC) using the columns of Chiralpak AD (amylase tris[3,5-dimethyl-phenylcarbamate]), Chiralpak AS (amylase tris[(S)-1-phenyl carbamate]), Chiralcel OD (cellulose tris[3,5-dimethylphenyl carbamate]), and Chiralcel OJ (cellulose tris[4-methyl benzoate]) with different chiral stationary phases. The differential toxicities of the enantiomers in aquatic systems were evaluated using the acute zebrafish (Danio rerio) toxicity test and the zebrafish embryo test. The enantiomers of LCT were separated completely on all the columns tested and detected by circular dichroism at 236 nm. Better separations were achieved at lower temperatures (e.g., 20°C) and lower levels of polar modifiers (,5%) in mobile phase. Ethanol was found to be a good modifier of the mobile phase for all the columns, although isopropanol acted better for the Chiralcel OD column. The (,)-enantiomer was >162 times more toxic than its antipode to zebrafish in the acute test. The embryo test indicated that the exposure to LCT enantioselectively induced crooked body, yolk sac edema, and pericardial edema and that the (,)-enantiomer was 7.2 times stronger than the (+)-enantiomer in 96-h mortality. The malformations were induced by the racemate and its (,)-enantiomer at lower concentrations tested (e.g., 50 ,g L,1), whereas the (+)-enantiomer induced malformations at relatively higher concentrations (,100 ,g L,1). These results suggest that the toxicological effects of chiral pesticides must be evaluated using their individual enantiomers. [source] Functionalized Poly(D,L -lactide) for Pulmonary Epithelial Cell CultureADVANCED ENGINEERING MATERIALS, Issue 4 2010Yuan-Min Lin Functional groups on a material surface affect the response of many cell types. As part of our strategy aimed at engineering lung tissue, we introduced functional groups into the surface of Poly(D,L -lactide) (PDLLA) films to improve its suitability for the culture of mature pulmonary epithelial cells (A549 line) using two different methods. The first method, aminolysis, can introduce primary amines into PDLLA films by transesterification using 1,15% of ethylenediamine in isopropanol. The second method, a branching modification, can generate amine-terminated or carboxylic acid-terminated tree-like branched architectures. All modified PDLLA surfaces exhibited lower water contact angles, i.e. are more hydrophilic than unmodified PDLLA. PDLLA treated with 15% ethylenediamine exhibited a rougher surface than the control, and PDLLA with branching modification had a droplet-like surface topography as visualized by atomic force microscopy (AFM). PDLLA treated with 15% ethylenediamine and branching modification with two and three generations enhanced the attachment of pulmonary epithelial cells measured using Hoechst dye. Immunostaining demonsatrated that amine-terminated branched architectures allowed for better focal adhesion point formation than the control 24,h after cell seeding. Furthermore, they also induced higher A549 cell populations and levels of activity after 4 days in culture measured using Hoechst dye and WST1 cell proliferation reagents, respectively. In contrast, carboxylic acid-terminated branching architectures were found to reduce the cell population size after 4 days. It was concluded that the concentration, type and distribution of surface functional groups can affect significantly the behavior of pulmonary epithelial cells growing on a PDLLA surface, and PDLLA film modified with two or three generations of amine-terminated branched architectures is a suitable 2D scaffold for the culture of of pulmonary epithelial cells. [source] Organic Single Crystals: Azeotropic Binary Solvent Mixtures for Preparation of Organic Single Crystals (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Mater. The inside cover of this issue illustrates the solution-phase self-assembly of organic single crystals by using azeotropic binary solvent mixtures, described by X. Li et al. on page 3610, and is a snap-shot taken during the self-assembly of tri-isopropylsilylethynyl pentacene single crystals from an azeotropic binary solvent mixture of isopropanol plus toluene, on a silicon substrate. These needle-like crystals were growing with time while floating in the bulk of the solution during solvent evaporation, with bright colors showing their birefringence. [source] Pigment Synthesis: PY181 Pigment Microspheres of Nanoplates Synthesized via Polymer-Induced Liquid Precursors (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Mater. A polymer-induced liquid precursor is used for a pigment yellow 181 crystal formed by chemical reaction in mixed solvents of water and isopropanol by direct azo coupling under the directing influence of a designed copolymer additive. This leads to a pigment with novel complex morphology and unusal properties, as shown by Cölfen et al. on page 2095. [source] PY181 Pigment Microspheres of Nanoplates Synthesized via Polymer-Induced Liquid PrecursorsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Yurong Ma Abstract Organic pigments are important crystalline substances, and their properties and applications rely on size and shape control. Pigment Yellow 181 (PY181) is an industrial azo pigment that is light and weatherfast and suitable for high temperature processing. One disadvantage is its needle-like shape in the default , -phase, which makes the pigment difficult to process in industry, e.g., in polymer melts, where a spherical structure would be ideal. Here, we show for the first time, that polymer-induced liquid precursor structures can be formed even in association to a chemical reaction. Furthermore, it is demonstrated that biomineralization principles can be exploited for the generation of advanced functional materials, such as pigments with novel complex morphology and different properties. Stable PY181 microspheres of nanoplates in the , -phase were obtained in mixed solvents of water and isopropanol by direct azo coupling under the directing influence of a designed copolymer additive aminobenzoylaminobenzamide-acetoacetyl-poly(ethylene imine)- block -poly(ethylene glycol) (ABABA-acetoacetyl-PEI- b -PEG). [source] Synthesis of morphologically different, metal absorbing aniline-formaldehyde polymers including micron-sized sphere using simple alcohols as morphology modifierJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Rik Rani Koner Abstract Aniline-formaldehyde condensate (AFC) is an amine functional group containing polymer. The sticky resinous nature of the polymer limits its usefulness. Synthesis of AFC in presence of methanol, isopropanol, t -butanol, n -octanol or glycerine formed solid cakes instead of resinous material. The scanning electron microscopic (SEM) picture of the polymer synthesized in presence of t -butanol shows the formation of micron sized spheroids while the presence of methanol, isopropanol, n -octanol and glycerine leads to amorphous polymer. The polymers were characterized with IR, MALDI-TOF mass and Energy Dispersive X-ray (EDAX) analysis. To probe the accessibility of the amine functional groups by external reagents and as an application, metal removal property of the polymers were tested using aqueous Cr(VI) solution. All the polymers remove Cr(VI) efficiently at pH 3 with extent of metal removal depends on their morphology. Polymer synthesized in presence of isopropanol removes , 66% Cr(VI) removal from an initial concentration of 9 mg/L. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Differential gene expression analysis using paraffin-embedded tissues after laser microdissectionJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2003Joung-Ok Kim Abstract Recent advances in laser microdissection allow for precise removal of pure cell populations from morphologically preserved tissue sections. However, RNA from paraffin-embedded samples is usually degraded during microdissection. The purpose of this study is to determine the optimal fixative for RNA extractions from laser microdissected paraffin-embedded samples. The integrity of RNA was evaluated with the intactness of 18S and 28S ribosomal RNA by electrophoresis and by the length of individual gene transcripts using RT-PCR. The various fixatives were methacarn (a combination of methanol, chloroform, and acetic acid) and several concentrations of ethanol and isopropanol. Methacarn was the optimal fixative for RNA preservation in paraffin-embedded tissues, which included liver, lung, kidney, muscle, and limb. Based on RT-PCR analysis, methacarn fixed samples exhibited the expected RNA sizes for individual genes such as glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) and bone-related genes (e.g., alkaline phosphatase and osteonectin). The laser microdissection technique with methacarn fixation was then applied to analyze the differential gene expression between hypertrophic and proliferative chondrocytes in the growth plate of long bone. The expression of type X collagen (ColX,1), a specific gene for hypertrophic chondrocytes, was only observed in hypertrophic chondrocytes, while type II collagen (Col2,1) was observed more broadly in the growth plate as anticipated. Thus, combining laser microdissection with methacarn fixation facilitates the examination of differentially expressed genes from various tissues. © 2003 Wiley-Liss, Inc. [source] Synthesis of carvacrol by Friedel,Crafts alkylation of o -cresol with isopropanol using superacidic catalyst UDCaT-5JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2009Ganapati D. Yadav Abstract BACKGROUND: Alkylation of o -cresol with propylene or isopropyl alcohol (IPA) over solid acid catalysts results in the formation of carvacrol, which finds potential applications in the synthesis of fine chemicals, intermediates, specialty chemicals, flavours and fragrances. RESULTS: The present work covers evaluation of novel mesoporous superacidic catalysts namely UDCaT-4, UDCaT-5 and UDCaT-6 in the greener synthesis of carvacrol. The catalysts are modified versions of zirconia showing high catalytic activity, stability and reusability. The catalytic activity increases in the following order: UDCaT-5 > UDCaT-4 > UDCaT-6 > sulfated zirconia. The process was optimized and a mathematical model developed to describe the reaction pathway in liquid phase. Carvacrol could be efficiently obtained with a selectivity up to 82% at an isopropanol conversion of 98% after 2 h over UDCaT-5 at 180 °C. CONCLUSION: The reaction is free from any external mass transfer as well as intraparticle diffusion limitations and is intrinsically kinetically controlled. An overall second-order kinetic equation was used to fit the experimental data. The activation energy was found to be 19.2 kcal/mol. The reaction was carried out without any solvent in order to make the process cleaner and greener. Copyright © 2009 Society of Chemical Industry [source] Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silicaJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2007Abd El-Aziz A Said Abstract Different ratios of phosphotungestic acid supported on silica gel were prepared by an impregnation method with PWA loadings ranging from 1 to 30% w/w and calcined at 350 and 500 °C for 4 h in a static air atmosphere. The catalysts were characterized by thermogravimety (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N2 adsorption measurements. The surface acidity and basicity of the catalyst were investigated by the dehydration,dehydrogenation of isopropanol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The gas-phase estrification of acetic acid with ethanol was carried out at 185 °C in a conventional fixed-bed reactor at 1 atm using air as carrier gas. The results clearly revealed that the catalyst containing 10% w/w PWA/SiO2 is the most active and delivers reaction selectively to ester with 85% yield. The Brønsted acid site resulting from hydroxylation of tungsten oxide plays the main role in the formation of ester. Copyright © 2007 Society of Chemical Industry [source] Surface properties and catalytic behavior of MoO3/SiO2 in esterification of acetic acid with ethanolJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2006Abd El-Aziz A Said Abstract A series of MoO3/SiO2 catalysts was prepared by an impregnation method with Mo loadings ranging from 1 to 50 wt%. The original and calcined samples at 400 °C were characterized by thermogravimetry (TG), differential thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, and nitrogen adsorption measurements. The surface acidity and basicity of the catalysts were investigated by the dehydration,dehydrogenation of isopropanol and the chemisorption of pyridine. The catalytic esterification of acetic acid with ethanol was carried out at 220 °C in a conventional fixed-bed reactor at 1 atm using air as a carrier gas. The results clearly revealed that silica,molybdena catalysts were active and selective towards the formation of ethyl acetate. Moreover, the catalyst containing 20 wt% MoO3 was the most active and selective one. The results emphasize the importance of the surface acid sites together with the specific surface area of the prepared catalyst, towards ester formation. Copyright © 2005 Society of Chemical Industry [source] Kinetics of esterification of palmitic acid with isopropanol using p -toluene sulfonic acid and zinc ethanoate supported over silica gel as catalystsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2004Roomana Aafaqi Abstract Kinetic data on the esterification of palmitic acid with isopropanol were obtained using homogeneous (para -toluene sulfonic acid, p -TSA) and heterogeneous (zinc ethanoate coated on silica gel, ZnA/SG) catalysts in a batch reactor. The ZnA/SG catalyst was prepared using a sol,gel technique. The esterification reaction was studied at different reaction temperatures (373,443 K), initial reactants molar ratio (1,5), catalyst loading (1,5 gcat dm,3) and water concentration in feed (0,15 vol%). A power law rate equation was used for homogeneous kinetics analysis. The Langmuir Hinshelwood Hougen Watson (LHHW) model was used for heterogeneous kinetics. The kinetic parameters of both models were obtained using Polymath software. The reaction parameters were used to obtain simulated values of conversion for both catalytic systems. The simulated values were compared with the experimental values and were in good agreement. Copyright © 2004 Society of Chemical Industry [source] Poster Sessions AP13: Novel Techniques and TechnologiesJOURNAL OF NEUROCHEMISTRY, Issue 2002J. K. Yao Studies of the antioxidant defense system and the monoamine metabolic pathways are often complicated by cumbersome analytical methods, which require separate and multistep extraction and chemical reaction procedures. Thus, measurements of multiple parameters are limited in relatively small biological samples. High performance liquid chromatography (HPLC) coupled with a Coulometric Multi-Electrode Array System (CMEAS) provides us a convenient and most sensitive tool to measure low molecular weight, redox-active compounds in biological sample. The deproteinized sample was analyzed on a HPLC coupled with a 16-channel CMEAS, which incremented from 60 to 960 mV in 60 mV steps. Each sample was run on a single column (Meta-250, 4.6 × 250 mm) under a 150-minute complex gradient that ranged from 0% B (A: 1.1% pentane sulfonic acid) to 20% B (B: 0.1 m lithium acetate in mixture of methanol, acetonenitrile and isopropanol), with a flow rate of 0.5 mL/min. We have developed an automated procedure to simultaneously measure various antioxidant, oxidative stress marker, and monoamine metabolites in a single column with binary gradient. No other chemical reactions are necessary. In order to reduce the running time and yet achieve a reproducible retention time by the autosampler injection, our gradient elution profile was modified to produce a shorter equilibration time and to compensate for the initial contamination of mobile phase B following the first injection. Without the use of two columns in series and peak suppresser/gradient mixer, we have simplified the previously published method to measure over 20 different antioxidants, oxidative stress markers and monoamine metabolites simultaneously in biological samples. [source] Experimental study of feasibility in kinetically-controlled reactive distillationAICHE JOURNAL, Issue 2 2005Madhura Chiplunkar Abstract Bifurcation studies predict limited ranges of feasibility for products in certain reactive distillations. These are closely related to the bifurcations in the singular points of dynamic models for simple reactive distillation (isobaric open evaporation with liquid phase reaction). A new dynamic model is described with constant vapor rate together with an experimental study for the reactive distillation of acetic acid with isopropanol to produce isopropyl acetate, catalyzed by Amberlyst-15 ion-exchange resin. An experimental apparatus with real-time measurement of liquid compositions based on Fourier transform infrared (FTIR) spectroscopy is described, and used to follow the composition dynamics at several initial conditions and Damköhler numbers (Da). The experimental results match model predictions that show four regions of behavior. For Da , 1, these show a stable node at acetic acid and several other fixed points as saddles. However, near Da , 2, both isopropanol and acetic acid are stable nodes and a quaternary singular point appears. The presence of two stable nodes requires the presence of a distillation boundary and, therefore, a limited feasibility for the bottom product compositions from continuous reactive distillation. For the reaction rates studied, the model predictions are closely consistent with the experimental findings, and are robust to variations in the vapor rate. These experiments are among the first to analyze the dynamics and feasibility in a kinetically-controlled reactive distillation and are consistent with previous studies for the reaction equilibrium limit, indicating the formation of a reactive azeotrope. © 2005 American Institute of Chemical Engineers AIChE J, 51: 464,479, 2005 [source] Kinetic modeling of the photocatalytic degradation of air-borne pollutantsAICHE JOURNAL, Issue 5 2004H. Ibrahim Abstract The photocatalytic conversion of organic model pollutants (acetone, acetaldehyde, and isopropanol) in a novel Photo-CREC-Air unit is considered. This photocatalytic unit features: (1) external near-UV lamps placed in parabolic reflectors, (2) a basket supporting the irradiated glass mesh holding TiO2 loadings to achieve high photoconversion rates, and (3) a fluid flow pattern securing high gas velocities in the near-mesh region. Given the high quantum efficiencies observed in Photo-CREC-Air and, as a result, the high prospects for this novel design, rate equations and associated mechanistic formulations are investigated. With this goal, a Langmuir,Hinshelwood model, involving a one-site model pollutant mechanism, is considered. The associated kinetic parameters with the related statistical indicators are established, using least-square nonlinear regression. It is found that this model is adequate for describing the photodegradation of acetone on both Degussa P25 and Hombikat UV-100. It is also observed that the same type of reaction rate model is less adequate for the photodegradation of acetaldehyde and isopropanol, in particular, for predicting the formation of carbon dioxide. © 2004 American Institute of Chemical Engineers AIChE J 50: 1017,1027, 2004 [source] The application of small porous particles, high temperatures, and high pressures to generate very high resolution LC and LC/MS separationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2007Robert Plumb Abstract The effect of combining sub-2 ,m porous particles with elevated operating temperatures on chromatographic performance has been investigated in terms of chromatographic efficiency, productivity, peak elution order, and observed operating pressure. The use of elevated temperature in LC does not increase the obtainable performance but allows the same performance to be obtained in less time. Increasing the column temperature did allow the use of longer columns, generating column efficiencies in excess of 100 000 plates and gradient peak capacities approaching 1000. Raising the temperature increased the optimal mobile phase linear velocity, negating somewhat the pressure benefits observed by reducing the solvent viscosity. When operating at higher temperature the analyte retention is not only reduced, but the order of elution will also often change. High temperature separations allowed exotic organic modifiers such as isopropanol to be exploited for alternative selectivity and faster analysis. Finally, care must be taken when using high temperature separations to ensure that the narrow peak widths produced do not compromise the quality of data obtained from detectors such as high resolution mass spectrometers. [source] Synthesis and Mechanism of Ferroelectric Potassium Tantalate Niobate Nanoparticles by the Solvothermal and Hydrothermal ProcessesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007Nian Wei High-purity KTa0.3Nb0.7O3 nanoparticles have been successfully synthesized by hydrothermal and solvothermal methods. The KOH concentration and the solvent composition have significant effects on the final products. The synthesis mechanism was discussed. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy investigations show that the typical samples solvothermally synthesized are nanosized, well crystallized, and single crystalline. The KTa0.3Nb0.7O3 shows a pseudo-cubic to tetragonal transition with increasing crystallite size. It is believed that supercritical isopropanol plays an important role in synthesizing KTa0.3Nb0.7O3 nanoparticles under milder conditions than the hydrothermal route. The present solvothermal method provides a new potential route for synthesizing ferroelectric potassium tantalate niobate material. [source] Degradation of the main components of cellulose-paint thinner by the mould Scopulariopsis brevicaulis cultured on rice hullsLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2003J. Alba Abstract Aims: Biodegradation of the main components of the cellulose-paint thinner (toluene, acetone, isopropanol and xylenes) by Scopulariopsis brevicaulis, isolated from a thinner biodegradation microbial consortium was investigated. Methods and Results: Our results showed that 90% of S. brevicaulis conidia survived after 4 weeks in a cellulose-paint thinner saturated atmosphere. The mould was able to grow under these environmental conditions with a low development of conidia. The biodegradation potential of S. brevicaulis was established with and without support material (rice hulls). Biodegradation without support was very limited, <10% for all the components quantified. There was notable thinner biodegradation when the fungus was grown on rice hulls. Conclusions: Our results suggest the potential use of fungi in biofiltration systems employed in biodegradation of the main components of the cellulose-paint thinner. Sigificance and Impact of the Study: This is the first report of volatile organic compounds biodegradation by this fungal species. [source] Patterned transparent zinc oxide films produced by sol,gel embossingPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008J. Rao Abstract A low cost zinc oxide embossing technique is reported as a method of fabricating structures relevant to a variety of applications. A zinc based sol,gel material was prepared from zinc acetate [Zn(C2H3O2)2], monoethanolamine [H2NC2H4OH] and isopropanol. The sol,gel was cast into a polydimethylsiloxane (PDMS) mould a track design, placed in contact with the substrate and dried under vacuum at 70 °C for 3 hours. The formed track pattern was further densified to provide a stable conductor film that retained the embossed shape. An optimum Zn sol,gel content of 0.6 M was identified. The embossed films had a transparency of greater than 83% in the visible region. The optical bandgap energy was evaluated to be 3.306 eV. The influence of ZnO sol,gel film synthesis and embossing parameters on the microstructure, morphology and optical transparency of fabricated structures is described. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Determination of quinolizidine alkaloids in Sophora tonkinensis by HPCEPHYTOCHEMICAL ANALYSIS, Issue 4 2005Pei-lan Ding Abstract A simple, rapid and reliable high-performance capillary electrophoresis method has been developed to determine quantitatively the alkaloid content of Sophora tonkinensis, a Chinese herb commonly known as shan-dou-gen. A total of seven quinolizidine alkaloids (cytisine, sophocarpine, matrine, lehmannine, sophoranol, oxymatrine and oxysophocarpine) could be readily separated within 15 min. The running buffer was 50 mM phosphate buffer (pH 2.5) containing 1% hydroxypropyl- , -cyclodextrin and 3.3% isopropanol in water. The applied voltage was 25 kV, the capillary temperature was 25°C, the detection wavelength was 200 nm and scopolamine butylbromide was used as internal standard. The method was used to analyse the chemical constituents of two commercial alternatives to shan-dou-gen. The alkaloid constituents of authentic shan-dou-gen gave a specific HPCE electropherogram that could be used to distinguish the drug from potential substitutes. Furthermore, the content of oxymatrine and the total content of the seven quinolizidine alkaloids could be used as quantitative markers in order to assess the quality of S. tonkinensis. Copyright © 2005 John Wiley & Sons, Ltd. [source] Trans influence in a mer -octahedral triiodidolanthanide: triiodidotris(tetrahydrofuran-,O)ytterbium(III)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Thomas J. Emge The structure of the six-coordinate title complex, [YbI3(C4H8O)3], is the first mer -octahedral form of an LnI3L3 lanthanide (Ln) compound with neutral L ligands, and is closely related to that of several of the seven-coordinate LnX3L4 series of compounds, where X = Cl, Br or I and L = tetrahydrofuran (THF), isopropanol, pyridine or water. A structural trans effect can be assigned to YbI3(THF)3, in contrast to the LnX3L4 compounds, where steric and crystal packing effects are significant. The Yb,I bond lengths are 2.9543,(4) and 2.9151,(6),Å for I trans and cis to I, respectively, and the Yb,O bond lengths are 2.299,(5) and 2.251,(3),Å for O trans and cis to I, respectively. The crystal packing allows for six contact distances as weak C,H...I interactions in the range 3.10,3.24,Å. The title molecule has a crystallographic twofold axis passing through a THF O atom, the trans I atom and the Yb atom. [source] | |||||||||||||||||||||||||||||||