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Isopropyl Alcohol (isopropyl + alcohol)
Selected AbstractsSolubility and phase separation of poly(L,D -lactide) copolymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Marja Rissanen Abstract In this study, the solubility and precipitation properties of medical-grade stereocopolymers were investigated. The solubility of the polymers was tested with eight different organic solvents and four nonsolvents. The solubility of poly(L,D -lactide) stereocopolymers was highly dependent on the L/D ratio of the copolymer. The phase-separation ability was tested by cloud-point titration with a solvent and a nonsolvent. The solvent was in all cases dichloromethane, and the nonsolvents were n -hexane, methanol, ethanol, and isopropyl alcohol. The results showed that n -hexane was the most efficient nonsolvent. Methanol and ethanol showed quite similar precipitation properties. Isopropyl alcohol was the least efficient nonsolvent of those studied. Also, the L/D ratio of the copolymer had an effect on the precipitation properties. The precipitation happened most easily when the L content was high. The molecular weight of the copolymer had only a slight effect on the phase separation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] FS09.2 Contact allergy to a commercial alcohol prep swabCONTACT DERMATITIS, Issue 3 2004James S Taylor Allergic contact dermatitis to prepackaged disposable alcohol prep swabs is infrequently reported. A 60-year-old woman developed repeated episodes of dermatitis at sites of injections and venipunctures. History and patch testing revealed contact allergy to Kendall Webcol alchol prep swabs. There were negative patch test results to isopropyl alcohol (IPA), but positive reactions to the Webcol swab, to the inner surface of the packaging foil, to two other brands of alcohol swabs, and to bacitracin. UV absorbance profile analysis revealed the presence of UV absorbing materials at peaks of 221 and 280 nm within commercial IPA samples, including one from Kendall, which were absent from reagent grade IPA. Reports of similar cases identified IPA, propylene oxide, or both as the allergens; when swab ingredients were negative, compound allergy was proposed. A recent report from Korea identified dodecyldiaminoethylglycine and IPA as the allergens in the commercial disinfectant swab. Although the exact allergen is undetermined in our case, it may represent a chemical compound or contaminant that is used or acquired during the manufacturing of the swabs or foils. [source] In vitro permeation of diclofenac sodium from novel microemulsion formulations through rabbit skinDRUG DEVELOPMENT RESEARCH, Issue 1 2005Gülten Kantarc Abstract In order to increase topical penetration of the nonsteroidal anti-inflammatory drug, diclofenac sodium, new microemulsion formulations were prepared to increase drug solubility and in vitro penetration of the drug. The influence of dimethyl sulfoxide and propylene glycol were also investigated as enhancers on the in vitro penetration of diclofenac sodium using Franz diffusion cells using excised dorsal rabbit skin. Factorial randomized design was performed to analyze the results of in vitro permeation studies. Microemulsions prepared with isopropyl alcohol were superior to those prepared with propanol. Enhancers had different effects depending on the formulation. Propylene glycol was superior to dimethyl sulfoxide when incorporated into isopropyl alcohol microemulsion, whereas dimethyl sulfoxide was superior to propylene glycol in propanol microemulsions. There were no observable histopathological differences between the skin of the control group and the treated groups at the light microscope level due to swelling of the skin tissue. The present study shows that microemulsion formulations containing isopropyl alcohol as co-surfactant and propylene glycol as enhancer represent a promising approach for a topical vehicle for diclofenac sodium. Drug Dev. Res. 65:17,25, 2005. © 2005 Wiley-Liss, Inc. [source] Analyses of alkaloids in different products by NACE-MSELECTROPHORESIS, Issue 22 2007Chen-Wen Chiu Abstract A simple method for the separation and characterization of five nicotine-related alkaloids by NACE employing UV and MS detections is described here for the first time. Several factors, including NACE parameters (compositions of running solution) and MS parameters (such as nature and flow rate of sheath liquid, pressure of nebulization gas, and flow rate of dry gas), were optimized in order to obtain both an adequate CE separation and high MS signals for the alkaloid compounds used in this study. A reliable CE separation of five alkaloids was achieved in 50,mM ammonium formate that was dissolved in an ACN/methanol mixture (50:50, v/v) of pH*,4.0 (apparent pH 4.0). The optimal electrospray MS measurement was carried out in the positive ionization mode using a coaxial sheath liquid composed of isopropyl alcohol and water in the ratio of 80:20 v/v at a flow rate of 180,,L/h. In addition, the proposed NACE method was also applied in the analyses of alkaloids in several products including chewing gums, beverages, and tobaccos. This NACE-MS method was found to provide a better detection ability and separation resolution for the analysis of nicotine alkaloids when compared to other aqueous CE-MS reports. [source] Porous Silicon-Based Optical Microsensors for Volatile Organic Analytes: Effect of Surface Chemistry on Stability and SpecificityADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Anne M. Ruminski Abstract Sensing of the volatile organic compounds (VOCs) isopropyl alcohol (IPA) and heptane in air using sub-millimeter porous silicon-based sensor elements is demonstrated in the concentration range 50,800 ppm. The sensor elements are prepared as one-dimensional photonic crystals (rugate filters) by programmed electrochemical etch of p++ silicon, and analyte sensing is achieved by measurement of the wavelength shift of the photonic resonance. The sensors are studied as a function of surface chemistry: ozone oxidation, thermal oxidation, hydrosilylation (1-dodecene), electrochemical methylation, reaction with dicholorodimethylsilane and thermal carbonization with acetylene. The thermally oxidized and the dichlorodimethylsilane-modified materials show the greatest stability under atmospheric conditions. Optical microsensors are prepared by attachment of the porous Si layer to the distal end of optical fibers. The acetylated porous Si microsensor displays a greater response to heptane than to IPA, whereas the other chemical modifications display a greater response to IPA than to heptane. The thermal oxide sensor displays a strong response to water vapor, while the acetylated material shows a relatively weak response. The results suggest that a combination of optical fiber sensors with different surface chemistries can be used to classify VOC analytes. Application of the miniature sensors to the detection of VOC breakthrough in a full-scale activated carbon respirator cartridge simulator is demonstrated. [source] Multiple Functionalization of Mesoporous Silica in One-Pot: Direct Synthesis of Aluminum-Containing Plugged SBA-15 from Aqueous Nitrate Solutions,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2008Y. Wu Abstract Aluminum-containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X-ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al-containing plugged silicas possess well-ordered hexagonal mesostructures with high surface areas (700,860 m2,g,1), large pore volume (0.77,1.05 cm3,g,1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma,atomic emission spectrometry results show that 0.7,3.0 wt,% aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43,60% aluminum species are incorporated into the skeleton of the Al-containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al-containing plugged silica has a similar morphology to that of traditional SBA-15. Furthermore, the Al-containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities. [source] Kinetics and mechanism of myristic acid and isopropyl alcohol esterification reaction with homogeneous and heterogeneous catalystsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2008Tuncer Yalçinyuva The reaction of myristic acid (MA) and isopropyl alcohol (IPA) was carried out by using both homogeneous and heterogeneous catalysts. For a homogeneously catalyzed system, the experimental data have been interpreted with a second order, using the power-law kinetic model, and a good agreement between the experimental data and the model has been obtained. In this approach, it was assumed that a protonated carboxylic acid is a possible reaction intermediate. After a mathematical model was proposed, reaction rate constants were computed by the Polymath* program. For a heterogeneously catalyzed system, interestingly, no pore diffusion limitation was detected. The influences of initial molar ratios, catalyst loading and type, temperature, and water amount in the feed have been examined, as well as the effects of catalyst size for heterogeneous catalyst systems. Among used catalysts, p -toluene sulfonic acid (p -TSA) gave highest reaction rates. Kinetic parameters such as activation energy and frequency factor were determined from model fitting. Experimental K values were found to be 0.54 and 1.49 at 60°C and 80°C, respectively. Furthermore, activation energy and frequency factor at forward were calculated as 54.2 kJ mol,1 and 1828 L mol,1 s,1, respectively. © 2008 Wiley Periodicals, Inc. 40: 136,144, 2008 [source] Immobilisation of the Pyrphos Ligand on Soluble Hyperbranched Supports and Use in Rhodium-Catalysed Hydrogenation in Ionic LiquidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009Jutta Abstract The immobilisation of the pyrphos ligand has been extended from highly symmetric dendrimers to less regular structured hyperbranched poly(ethylene imines). Cationic dendritic pyrphos-rhodium(norbornadiene) [pyrphos-Rh(NBD)] complexes have been synthesised using poly(propylene imine) (PPI) and poly(amido amine) (PAMAM) dendrimers as supports bearing between 4 and 64 potential catalytically active sites at their periphery as well as pyrphos-Rh(NBD) complexes tethered to hyperbranched poly(ethylene imines) carrying on average 9 to 139 functionalities located throughout the whole supporting structure. These immobilised systems have been used as catalysts for the hydrogenation of Z -methyl ,-acetamidocinnamate. With the PPI, PAMAM, and hyperbranched poly(ethylene imine)-bound pyrphos-Rh(NBD) omplexes as catalysts, hydrogenations were carried out in methanol, and a decrease in activity and selectivity was observed with increasing size of the macromolecular support. Furthermore, the polycationic catalysts were tested in a liquid/liquid-biphasic system consisting of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate {[BMIM] [BF4]} and isopropyl alcohol. Using the PPI-, PAMAM-, and PEI-immobilised systems, a strong negative "dendritic effect" with increasing molecular size was observed with respect to the catalytic activity, the stereoinduction, and the recyclability. The PPI-bound rhodium(I)-complexes of generations one and two showed good reusability; even after triple recycling, with no loss of activity or selectivity being noted. It has been demonstrated that in this case the catalytic behaviour of hyperbranched systems is essentially similar to that of the related dendritic model system. [source] Second Generation Sol-Gel Encapsulated Lipases: Robust Heterogeneous BiocatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6-7 2003Manfred Abstract The original procedure for the encapsulation of lipases in sol-gel materials produced by the fluoride-catalyzed hydrolysis of mixtures of RSi(OCH3)3 and Si(OCH3)4 has been improved considerably. This involves higher enzyme loading, variation of the alkylsilane precursor, and the use of additives such as isopropyl alcohol, 18-crown-6, Tween,80®, methyl-,-cyclodextrin and/or KCl. A dramatic increase in enzyme activity is observed. The sol-gel lipase immobilizates are also excellent catalysts in the kinetic resolution of chiral alcohols and amines, recycling without any substantial loss in enantioselectivity and a residual activity of 70% being possible even after 20 reaction cycles. [source] Solubility and phase separation of poly(L,D -lactide) copolymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Marja Rissanen Abstract In this study, the solubility and precipitation properties of medical-grade stereocopolymers were investigated. The solubility of the polymers was tested with eight different organic solvents and four nonsolvents. The solubility of poly(L,D -lactide) stereocopolymers was highly dependent on the L/D ratio of the copolymer. The phase-separation ability was tested by cloud-point titration with a solvent and a nonsolvent. The solvent was in all cases dichloromethane, and the nonsolvents were n -hexane, methanol, ethanol, and isopropyl alcohol. The results showed that n -hexane was the most efficient nonsolvent. Methanol and ethanol showed quite similar precipitation properties. Isopropyl alcohol was the least efficient nonsolvent of those studied. Also, the L/D ratio of the copolymer had an effect on the precipitation properties. The precipitation happened most easily when the L content was high. The molecular weight of the copolymer had only a slight effect on the phase separation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [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] Adsorption equilibrium of amino acids and antibiotics on non-ionic polymeric sorbentsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2004Jae Wook Lee Abstract Adsorption equilibria of two amino acids (phenylalanine and tryptophan) and two antibiotics (penicillin G and cephalosporin C) from aqueous solutions onto non-ionic polymeric sorbents (XAD-4 and XAD-16) were investigated under various experimental conditions such as pH, temperature and organic solvents. The assumption that amino acids adsorbed on polymeric sorbents were desorbed by competitive adsorption with organic solvent as a desorbate was verified using binary adsorption data for amino acids (phenylalanine and tryptophan) and organic solvents (isopropyl alcohol and methanol) on XAD-4 and XAD-16. The experimental data were predicted by using multicomponent adsorption models of an Extended-Langmuir (EL) equation and an ideal adsorbed solution theory (IAST) based on the Langmuir equation as a single-component isotherm. Copyright © 2004 Society of Chemical Industry [source] Gas phase esterification of acetic acid with ethanol over MoO3 supported on AlPO4 and the effect of modification with phosphomolybdic acid and Ce4+ ionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2003Abd El-Aziz A Said Abstract A series of AIPO4,MoO3 (APM) systems with various molybdena loadings (5,50) mol %, same modified with phosphomolybdic acid (PMA) and cerium ions, were prepared by an impregnation method and calcined at 400 °C, except for the samples modified with PMA which were calcined at 350 °C for 4 h. The catalysts were characterized by TG/DTG, XRD, IR spectroscopy, N2 adsorption and electrical conductivity measurements. The surface acidity and basicity of the catalysts were determined by adsorption of pyridine and the dehydration,dehydrogenation of isopropyl alcohol. The catalytic esterification of acetic acid with ethanol was carried out in a convention fixed bed reactor. The results clearly revealed that the catalyst with a composition of 10 mol % MoO3 (APM10) was the most active and selective catalyst for the production of ethyl acetate. Moreover, the yield of ethyl acetate increases on addition of PMA into APM10 while it decreases on the addition of Ce4+ ions. These results were correlated with structure, semiconductivity and the acid,base properties of the prepared catalysts. Copyright © 2003 Society of Chemical Industry [source] Characterization of the Products Formed by the Reaction of Trichlorocyanuric Acid with 2-PropanolJOURNAL OF FORENSIC SCIENCES, Issue 6 2009P. Mark L. Sandercock Ph.D. Abstract:, We report a recent investigation into the death of a cat that was initially thought to involve intentionally burning the animal via the use of an ignitable liquid. The exposure of the animal to flame was ruled out. Instead, forensic investigation revealed the intentional mixing together of a common outdoor swimming pool chlorinator, trichlorocyanuric acid (TCCA), and 2-propanol (aka, isopropyl alcohol or rubbing alcohol). The reaction of these two chemicals resulted in the formation of cyanuric acid residue, hydrochloric acid, and the evolution of a significant volume of chlorine gas. Further ,-chlorination side reactions also occurred between 2-propanol and TCCA to produce a variety of chlorinated 2-propanone species that were detected on the submitted evidence. The identification of the products of both the main reaction and the side reactions allowed the authors to determine what chemicals were originally mixed together by the culprit. [source] Synthesis and antimicrobial activity of 6,6,-arylidene-bis-[5-hydroxy-9-methyl-2,3-diaryl thieno[3,2- g -]thiocoumarins]JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2005P. Vijay Kumar Reddy A variety of novel 6,6,-arylidene-bis-[5-hydroxy-9-methyl-2,3-diaryl-thieno[3,2- g]thiocoumarins] 3a-d, 4a-d, 5a-d, and 6a-d were obtained by a reaction between 5-hydroxy-9-methyl-2,3-diarylthieno[3,2- g]thiocoumarins 1a-d with aromatic aldehydes 2a-d in isopropyl alcohol. The synthesized compounds were tested for their antimicrobial activity. [source] Experimental and theoretical study of the influence of pressure on SCWOAICHE JOURNAL, Issue 11 2006M. D. Bermejo Abstract It is well known that pressure is an important parameter in the SCWO process, because it produces changes in the phase behavior and thermodynamics properties of the system. The influence of pressure on the oxidation efficiency of feeds containing isopropyl alcohol as fuel and acetic acid as waste was studied in an autothermal adiabatic transpiring wall reactor at pilot-plant scale, at pressures from 13 to 25 Mpa, and temperatures from 600 to 750°C. It was found that reaction temperature decreased between 40 and 100°C, when pressure was lowered, and, subsequently TOC removal decreased. At higher-temperatures, the decreasing of TOC removal due to pressure difference was reduced. The process was simulated at different pressures using a mathematical model previously developed for the reactor. The Anderko-Pitzer EoS, especially developed for aqueous systems at high-temperatures and pressures, was used to have accurate values of the heat capacities of the reaction mixture. It was found that having into account only the effect of pressure in the thermodynamical properties and in the concentration of the reagents, the experimental results could not be explained. Thus, the influence of the pressure in the reaction rate equation had to be considered. Results were qualitatively reproduced considering the reaction rate constant variable with pressure, using a constant volume of activation of ,1400 cm3/mol. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Optimal design of azeotropic batch distillationAICHE JOURNAL, Issue 3 2006M. C. Mussati Abstract This study explores integrating models with different degrees of detail for optimizing azeotropic batch distillation systems. A detailed dynamic model is used from outside the optimization program both to verify feasibility of the design and to update the parameters needed by the optimization model. The updated parameters are the constant relative volatilities between pseudo-components, used in a binary Fenske,Underwood,Gilliland-type model. The approach was used to optimize the design of a batch process for the recovery of spent isopropyl alcohol, which works cyclically to separate the excess water, satisfying an environmentally acceptable specification, and using cyclohexane as entrainer, which in turn is recovered in the same process and recycled. The approach permitted optimizing the batch sizes, number of separation stages, the reflux ratios of a piecewise constant multilevel reflux policy, the extent of each separation, and the size of the intermediate cuts to be recycled, with affordable computation and problem setup times. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Multiscale approach to investigate the radiochemical degradation of epoxy resins under high-energy electron-beam irradiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006N. Longiéras Abstract A multiscale investigation of the degradation mechanism of two epoxy systems exposed to electron-beam irradiation under a helium atmosphere was carried out with a variety of analytical methods, including high-resolution solution- and solid-state NMR spectroscopy, NMR relaxometry, infrared spectroscopy, sterical exclusion chromatography, and differential scanning calorimetry. As a first step, we studied a linear phenoxy polymer, poly(2-hydroxyether of bisphenol A), which provided a basis for the investigation of the degradation of a more complex, insoluble epoxy,amine network, diglycidyl ether of bisphenol A/triethylene tetramine. Among different structural modifications, the main degradation process was shown to produce in both cases a chain scission. For the phenoxy resin, the hydroxypropylidene moiety was identified as the fragile site leading to the formation of two phenolic chain ends and acetone and isopropyl alcohol as low-molecular-weight products. All methods, ranging from molecular to supramolecular scales, were shown to correlate both qualitatively and quantitatively. Experimental results obtained with diglycidyl ether of bisphenol A/triethylene tetramine evidenced a different degradation scheme occurring at the ethylene amine part and producing a dangling vinyl amine as the major degradation product. A selective increase in the molecular mobility at this site was confirmed by a two-dimensional, local-field wide-line separation experiment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 865,887, 2006 [source] THE INFLUENCE OF SOLUTION VISCOSITY AND DIFFERENT VISCOSIFYING AGENTS ON APPLE JUICE FLAVORJOURNAL OF SENSORY STUDIES, Issue 3 2000SHANE WALKER ABSTRACT Viscosifying agents are used in foods as thickeners to produce improved mouthfeel and as stabilizers to prevent settling out of particulate matter. While viscosifying agents are also known to influence the sensory profile of the products in which they are used, previous studies have examined the effects of viscosifying agents at levels that are not typical of those used in foods. The current study used a descriptive analysis panel to examine the effects of both viscosity and viscosifying agent on the sensory properties of apple juice using three viscosifying agents (carboxymethylcellulose, xanthan and pectin) at levels of usage similar to those recommended for drink products. Gas chromatography-flame ionization detection and gas chromatography-mass spectrometry were conducted on the samples to relate alteration in physico-chemical parameters to changes in sensory profile. Results from the descriptive panel showed that increasing viscosity tended to decrease some aspects of flavor intensity (sourness and cooked apple odor). Individual viscosifying agents were shown to have specific effects on odor and flavor attributes, e.g. pectin enhanced cereal odor. Gas chromatography-flame ionization detection and mass spectrometry suggested that this effect was related to isopropyl alcohol contributed by the pectin in solution. Pectin also suppressed honey odor and flavor, lemon odor and cooked apple flavor. [source] Simultaneous determination of digoxin and digitoxin by micellar electrokinetic chromatography and application to drug formulationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2003Hsiu-Hui Tseng Abstract A simple micellar electrokinetic chromatographic method is described for simultaneous determination of digoxin and digitoxin. The simultaneous analysis of digoxin and digitoxin was performed in Tris buffer (10 mM; pH 9) with 90 mM sodium dodecyl sulfate and 10% isopropyl alcohol as an anionic surfactant and organic modifier. Under these conditions, good separation with high efficiency is achieved in short analysis times. Several parameters affecting the separation of the drugs were studied, including the pH and concentrations of the Tris buffer and sodium dodecyl sulfate. The linear range of the method for the determination of digoxin and digitoxin was over 0.01,0.3 mg/mL; the detection limit (signal to noise ratio = 3; injection 3.5 kPa 3 s) was 4 and 6 ,g/mL, respectively. Application of the proposed method to the determination of digoxin in commercial tablets and in injections proved to be feasible. [source] Organic,Inorganic Interactions in Poly(trimethylene carbonate),Titania HybridsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2009Elisa Cortecchia Abstract Polycarbonate,titania hybrids have been synthesized by a sol,gel reaction, starting from poly(trimethylene carbonate) (PTMC) and titanium isoproproxide in different ratios. PTMC with a given chain length was obtained by ring opening polymerization. FT-IR spectra reveal the presence of TiOC covalent bonds between organic and inorganic phases, and their number increases with increasing inorganic phase content. Solvent extractions show that hybrid soluble fraction contains low PTMC chains with isopropoxide ends, which suggests that TiOC bond formation is mainly promoted by transesterification reactions of isopropyl alcohol onto the polymer chain, catalyzed by Ti compounds. Hybrid thermal properties reflect the combined effect of the decrease of PTMC molecular weight and of bond formation between PTMC and the inorganic network. The nanometric dimension of the TiO2 domains, confirmed by atomic force microscopy, provides optically transparent hybrids. [source] Glass-Transition Temperature (Tg) of Free-Radically Prepared Polyacrylonitrile by Inverse Gas Chromatography, 2,.MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2002Molecular-Weight Dependence of Tg of Two Different Types of Aqueous Polymers Abstract The molecular-weight dependence of the glass-transition temperature (Tg) of a series of atactic polyacrylonitriles (PAN)s was studied by inverse gas chromatographic (IGC) analysis. PANs having different molecular weights were prepared by either; (i) the addition of isopropyl alcohol as a chain-transfer agent, or (ii) a scission reaction induced by the addition of alkali (NaOH) to a solution (N,N -dimethylformamide solution, at 25,°C) of the resulting polymer. The intrinsic viscosity [,] was in the range of 10.9,0.1 (dl,·,g,1), which corresponds to a viscosity-averaged molecular weight (Mv) of 1,590,000,3,000. As part of the results, a side reaction, which saw the conversion of the nitrile (CN) groups of PAN into amide (CONH2) and/or carboxylic acids (COOH) groups by alkali, was found to occur. The typical molecular-weight dependence of the Tg in free-radically prepared PAN was discussed in connection with a chain-transfer mechanism in an aqueous medium. Molecular-weight dependence of the Tg for PAN (WA). An error bar is given by a short vertical arrow. [source] Photochemically Cross-linked Poly(aryl ether ketone) RingsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2006Ian Teasdale Abstract Summary: Macrocyclic phenyl ether ketones were prepared via pseudo high dilution condensation. Irradiation of these rings with UV light in a solution containing isopropyl alcohol as hydrogen donor resulted in a photo-induced reduction of benzophenone to benzopinacol and the formation linked macrocycles. These rings can be heated to undergo ring-opening polymerization and produce a polymer network or they can be added to a polycondensation reaction to prepare poly(ether ether ketones) with variable degrees of cross-linking. Photochemical cross-linking of PEK rings and ring opening polymerization (n: 2,6). (a) h,, iPrOH, DCM; (b) CsF, 260,°C (polymer 3); (c) 4,4,,difluorobenzophenone, hydroquinone, diphenylsulphone, K2CO3, 260,°C (2% polymer 4; 6% polymer 5). [source] Phospholipids in liquid chromatography/mass spectrometry bioanalysis: comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effectsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2009Yuan-Qing Xia Because plasma phospholipids may cause matrix effects in bioanalytical liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods, it is important to establish optimal mass spectrometric techniques to monitor the fate of phospholipids during method development and application. We evaluated three MS/MS techniques to monitor phospholipids using positive and negative electrospray ionization (ESI). The first technique is based on using positive precursor ion scan of m/z 184, positive neutral loss scan of 141 Da and negative precursor ion scan of m/z 153. The second technique is based on using class-specific positive and negative selected reaction monitoring (SRM) transitions to monitor class-representative phospholipids. The third technique, previously reported, utilizes in-source collision-induced dissociation (CID)-based positive SRM of m/z 184,,,184. We recommend the all-inclusive technique 1 for use in qualitative assessment of all classes of phospholipids and technique 2 for use in quantitative assessment of class-representative phospholipids. Secondly, we evaluated the elution behaviors of the plasma phospholipids under different reversed-phase mobile phase conditions. The phospholipid-eluting strength of a mobile phase was mainly dependent on the type and amount (%) of the organic eluent and the strength increased in the order of methanol, acetonitrile and isopropyl alcohol. Under the commonly used gradient and isocratic elution schemes in LC/MS/MS bioanalysis, not all the phospholipids are eluted off the column. Thirdly, we investigated the association between phospholipids and matrix effects in positive and negative ESI using basic, acidic and neutral analytes. While the phospholipids caused matrix effects in both positive and negative ESI, the extent of ionization suppression was analyte-dependent and was inversely related to the retention factor and broadness of the phospholipids peaks. The lysophospholipids which normally elute earlier in reversed-phase chromatography are more likely to cause matrix effects compared to the later-eluting phospholipids in spite of the larger concentrations of the latter in plasma. Copyright © 2009 John Wiley & Sons, Ltd. [source] Liquid chromatographic/mass spectrometry assay of bromotetrandrine in rat plasma and its application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Naining Song Abstract A rapid and sensitive liquid chromatography,tandem mass spectrometric method (LC-MS/MS) for the determination of bromotetrandrine in rat plasma has been developed and applied to pharmacokinetic study in Sprague,Dawley (SD) rats after a single oral administration. Sample preparation involves a liquid,liquid extraction with n -hexane,dichlormethane (65:35, containing 1% 2-propanol isopropyl alcohol, v/v). Bromotetrandrine and brodimoprim (internal standard, IS) were well separated by LC with a Dikma C18 column using methanol,ammonium formate aqueous solution (20 mm) containing 0.5% formic acid (60:40, v/v) as mobile phase. Detection was performed on a triple quadrupole mass spectrometer in multiple reaction monitoring mode. The ionization was optimized using ESI(+) and selectivity was achieved using MS/MS analysis, m/z 703.0 , 461.0 and m/z 339.0 , 281.0 for bromotetrandrine and IS, respectively. The present method exhibited good linearity over the concentration range of 20,5000 ng/mL for bromotetrandrine in rat plasma with a lower limit of quantification of 20 ng/mL. The intra- and inter-day precisions were 2.8,7.5% and 3.2,8.1%, and the intra- and inter-day accuracy ranged from ,4.8 to 8.2% and ,5.6 to 6.2%, respectively. The method was successfully applied to a pharmacokinetic study after a single oral administration to SD rats with bromotetrandrine of 50 mg/kg. Copyright © 2009 John Wiley & Sons, Ltd. [source] Chiral separation of rac -Ornidazole and detection of the impurity of (R)-Ornidazole in (S)-Ornidazole injection and raw materialCHIRALITY, Issue 8 2006Jianquan Huang Abstract (S)-Ornidazole is a subject of research as an antifertility agent in male animals at present. However, there seems to be no relative report on chiral separation for rac -Ornidazole, which has been used as an effective medicine for more than 30 years. In this article, the chiral separation of rac -Ornidazole on a Chiralcel OB-H column based on normal-phase high-performance liquid chromatography (NP-HPLC) is investigated and the methodology for detection of impurity of (R)-Ornidazole in (S)-Ornidazole injection and raw material is established. The novel mobile phase is utilized by mixing n -hexane, methanol and isopropyl alcohol (95:4:1, v/v/v) instead of the typical mobile phase of n -hexane and isopropyl alcohol, although the methanol, which offers a good resolution factor for the enantiomeric separation in this system, is not recommended on the Chiralcel OB-H column according to the instruction supplied by Daicel Chemical Ind., LTD (Japan). Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||