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Organic Solvents (organic + solvent)
Kinds of Organic Solvents Terms modified by Organic Solvents Selected AbstractsChemInform Abstract: Potassium Permanganate/Carboxylic Acid/Organic Solvent: A Powerful Reagent for Enone Oxidation and Aryl Coupling Reactions.CHEMINFORM, Issue 47 2008Ayhan S. Demir Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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] Investigation of p-type macroporous silicon formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005C. Lévy-Clément Abstract Nanopores and macropores can be formed electrochemically on p-type silicon depending on the silicon resistivity and composition of the electrolyte. In order to understand if the structural dimensionality of the porous p-type Si, either nanopore or macropore formation, depends on the electrochemical process at the Si/electrolyte interface, in situ pulsed surface photovoltage (SPV) and photoluminescence (PL) measurements have been undertaken. The SPV and PL studies have been made as a function of the applied current density as well as the electrolyte composition (aqueous or in presence of organic solvent) and the silicon doping density. Main results show that the Si surface is well passivated with preferential formation of ionic species and the Si band bending is around 100 mV, during porous Si formation. It varies slightly with the doping density, but is not affected by the composition of the electrolyte (HF/water and HF/organic solvent). This demonstrates that the chemistry of the electrolyte plays a major role in the formation of macroporous and nanoporous Si, but has still to be determined. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Acceleration of Short Helical Peptide Conformational Dynamics by Trifluoroethanol in an Organic SolventCHEMBIOCHEM, Issue 7 2005Matthew Kubasik Prof. Solvent dependency. The influence of the cosolvent trifluorethanol on the rate of enantiomerization of an octameric peptide (see figure) in CD2Cl2 solution is described. Kinetic data have been taken over a range of temperatures, thus allowing for a discussion of the enthalpic and entropic origins of the catalytic effect. [source] Effective Reductive Amination of Carbonyl Compounds with Hydrogen Catalyzed by Iridium Complex in Organic Solvent and in Ionic Liquid.CHEMINFORM, Issue 45 2005Daisuke Imao Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Optimum Conformational Flexibility of Subtilisin to Maximize the Enantioselectivity for Subtilisin-Catalyzed Transesterification in an Organic Solvent with an Addition of Dimethyl Sulfoxide.CHEMINFORM, Issue 44 2001Keiichi Watanabe 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] Chemoselective Oxidation of Alcohols by a H2O2,Pt Black System under Organic Solvent- and Halide-Free ConditionsCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Yoshihiro Kon Dr. Abstract Environmentally benign oxidation of allylic alcohols by platinum black catalyst with aqueous hydrogen peroxide to give the corresponding ,,,-unsaturated carbonyl compounds in high yield is presented. Reactions are carried out under organic solvent- and halide-free conditions. The platinum black catalyst is commercially available and is found to be reusable at least seven times before significant loss of catalytic activity. The operation is very simple, even in a hectogram-scale synthesis, and gives corresponding carbonyl compounds in over 90,% yield. The effective oxidation of benzyl and secondary alcohols are also described. [source] A Combinatorial Approach for Colorimetric Differentiation of Organic Solvents Based on Conjugated Polymer-Embedded Electrospun FibersADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Jaewon Yoon Abstract A combinatorial approach for the colorimetric differentiation of organic solvents is developed. A polydiacetylene (PDA)-embedded electrospun fiber mat, prepared with aminobutyric acid-derived diacetylene monomer PCDA-ABA 1, displays colorimetric stability when exposed to common organic solvents. In contrast, a fiber mat prepared with the aniline-derived diacetylene PCDA-AN 2 undergoes a solvent-sensitive color transition. Arrays of PDA-embedded microfibers are constructed by electrospinning poly(ethylene oxide) solutions containing various ratios of two diacetylene monomers. Unique color patterns are developed when the conjugated polymer-embedded electrospun fiber arrays are exposed to common organic solvents in a manner which enables direct colorimetric differentiation of the tested solvents. [source] Molecular Design of Superabsorbent Polymers for Organic Solvents by Crosslinked Lipophilic Polyelectrolytes,ADVANCED FUNCTIONAL MATERIALS, Issue 24 2008Toshikazu Ono Abstract Molecular design of lipophilic polyelectrolyte gels as superabsorbent polymers that exhibit a high degree of swelling in less-polar and nonpolar organic solvents is demonstrated. A small amount of tetraalkylammonium tetraphenylborate with long alkyl chains as a lipopholic ion pair is incorporated into crosslinked polyacrylates with variable alkyl chain lengths to provide novel lipophilic polyelectrolyte gels. Their swelling degree becomes more than 100 times as much as their dried weights in various organic solvents. The high effectiveness of the swellable solvents shifts to the polar ones by decreasing the length of the alkyl chain. Swelling or collapsing of the lipophilic polyelectrolyte gels originates from both incompatibility of the polymer chains in the media and dissociation of ionic groups. Thus, a unique superabsorbency is observed when the polymer chains have good compatibility with the solvents and the solvents have relatively high polarities enough to dissociate the ionic groups. By varying the polarity of the neutral monomer in these polyelectrolyte gels, the design of gels that can absorb solvents of nearly any polarity is demonstrated. [source] Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents,ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008Michael J. Frampton Abstract Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water-soluble polyfluorene- alt -biphenylene ,-cyclodextrin (CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organic-soluble polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4-dimethylaminopyridine; and 98% butanoic anhydride/pyridine/4-dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and simplifying the time-resolved fluorescence decay. The organic-soluble polyrotaxanes were processed into polymer light-emitting diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer. [source] (R,S)-Azolides as Novel Substrates for Lipase-Catalyzed Hydrolytic Resolution in Organic SolventsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Pei-Yun Wang Abstract Azolides, that is, N -acylazoles, as versatile acylation reagents are well characterized in the literature, in which the azole structure can not only act as a better leaving group but also make the carbonyl carbon more electrophilic and susceptible to nucleophilic attack. It is therefore desirable to combine this unique property and lipase resolution ability in the development of a new resolution process for preparing optically pure carboxylic acids. With the Candida antarctica lipase B (CALB) - catalyzed hydrolysis of (R,S)- N -profenylazoles in organic solvents as the model system, (R,S)- N -profenyl-1,2,4-triazoles instead of their corresponding ester analogues were exploited as the best substrates for preparing optically pure profens, i.e., 2-arylpropionic acids. The structure-reactivity correlations for the (R,S)-azolides in water-saturated methyl tert -butyl ether (MTBE) at 45,°C coupled with a thorough kinetic analysis were further employed for elucidating the rate-limiting formation of a tetrahedral adduct without CN bond breaking or with moderate CN bond breaking concerted with CO bond formation in the acylation step. The advantages of easy substrate preparation, high enzyme reactivity and enantioselectivity, and easy recovery of the product and remaining substrate by aqueous extraction demonstrate the potential of using (R,S)-azolides as novel substrates for the enzymatic resolution process. [source] Organocatalytic Asymmetric syn -Aldol Reactions of Aldehydes with Long-Chain Aliphatic Ketones on Water and with Dihydroxyacetone in Organic SolventsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2008Ming-Kui Zhu Abstract An on-water, asymmetric, and direct syn -aldol reaction of aliphatic ketones with aromatic aldehydes catalyzed by a primary amino acid-based organocatalyst afforded the syn -aldol adducts in high yields with excellent diastereo- and enantioselectivities (up to > 20/1 dr, >99% ee), and a highly enantioselective syn -aldol reaction of dihydroxyacetone with a variety of aldehydes in THF proceeded with 14/1 to >20/1 dr and 92 to >99% ee. Water not only accelerated the reaction, but also enhanced the enantioselectivity. This positive water effect might arise from the hydrogen bond formed between a pendant hydroxy group of surface water molecules at the hydrophobic interface with the amide oxygen of the organocatalyst, which increases the acidity of the amide NH and thereby strengthens the related hydrogen bond formed with the aldehyde. [source] Fluorescence Lifetimes Study of ,-Tocopherol and Biological Prenylquinols in Organic Solvents and Model MembranesPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2006Jerzy Kruk ABSTRACT We have found that for biological prenyllipids, such as plastoquinol-9, ,-tocopherol quinol, and ,-tocopherol, the shortest fluorescence lifetimes were found in aprotic solvents (hexane, ethyl acetate) whereas the longest lifetimes were those of ubiquinonol-10 in these solvents. For all the investigated prenyllipids, fluorescence lifetime in alcohols increased along with an increase in solvent viscosity. In a concentrated hexane solution, the lifetimes of prenylquinols considerably decreased. This contrasts with methanol solutions, which is probably due to the self-association of these compounds in aprotic solvents. We have also found a correlation of the Stokes shift of prenyllipids fluorescence with the orientation polarizability of the solvents. Based on data obtained in organic solvents, measurements of the fluorescence lifetimes of prenyllipids in liposomes allowed an estimation of the relative distance of their fluorescent rings from the liposome membrane surface, and was found to be the shortest for ,-tocopherol quinol in egg yolk phosphatidyl-choline liposomes, and increased in the following order: ,-tocopherol in dipalmitoyl phosphatidylcholine liposomes < ,-tocopherol < plastoquinol-9 < ubiquinol-10 in egg-yolk phosphatidylcholine liposomes. [source] Rules for Optimization of Biocatalysis in Organic Solvents,BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Colja Laane First page of article [source] Improving the Industrial Production of 6-APA: Enzymatic Hydrolysis of Penicillin G in the Presence of Organic SolventsBIOTECHNOLOGY PROGRESS, Issue 6 2003Olga Abian The hydrolysis of penicillin G in the presence of an organic solvent, used with the purpose of extracting it from the culture medium, may greatly simplify the industrial preparation of 6-APA. However, under these conditions, PGA immobilized onto Eupergit displays very low stability (half-life of 5 h in butanone-saturated water) and a significant degree of inhibition by the organic solvent (30%). The negative effect of the organic solvent strongly depended on the type of solvent utilized: water saturated with butanone (around 28% v/v) had a much more pronounced negative effect than that of methylisobutyl ketone (MIBK) (solubility in water was only 2%). These problems were sorted out by using a new penicillin G acylase derivative designed to work in the presence of organic solvents (with each enzyme molecule surrounded by an hydrophilic artificial environment) and a suitable organic solvent (MIBK). Using such solvent, this derivative kept its activity unaltered for 1 week at 32 °C. Moreover, the enzyme activity was hardly inhibited by the presence of the organic solvent. In this way, the new enzyme derivative thus prepared enables simplification of the industrial hydrolysis of penicillin G. [source] ChemInform Abstract: Highly Regioselective Propanoylation of Dihydroxybenzenes Mediated by Candida antarctica Lipase B in Organic Solvents.CHEMINFORM, Issue 16 2008Toshifumi Miyazawa Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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] 9-Fluorenylphosphines for the Pd-Catalyzed Sonogashira, Suzuki, and Buchwald,Hartwig Coupling Reactions in Organic Solvents and Water.CHEMINFORM, Issue 28 2007Christoph A. Fleckenstein Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] D-Aminoacylase-Catalyzed Markovnikov Addition of Azoles to Vinyl Esters in Organic Solvents.CHEMINFORM, Issue 6 2006Wei-Bo Wu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Lyophilization of Lipase Together with Ionic Compounds Generates Highly Enantioselective and Solvent-Sensitive Lipase in Organic Solvents.CHEMINFORM, Issue 24 2005Shin-ichi Ueji Abstract For Abstract see ChemInform Abstract in Full Text. [source] Lipase-Catalyzed Selective Benzoylation of 1,2-Diols with Vinyl Benzoate in Organic Solvents.CHEMINFORM, Issue 4 2004Pierangela Ciuffreda Abstract For Abstract see ChemInform Abstract in Full Text. [source] Pyridine-Containing Cholesterols as Versatile Gelators of Organic Solvents and the Subtle Influence of Ag(I) on the Gel Stability.CHEMINFORM, Issue 23 2003Shin-ichiro Kawano Abstract For Abstract see ChemInform Abstract in Full Text. [source] Protease Immobilization on ,-Fe2O3/Fe3O4 Magnetic Nanoparticles for the Synthesis of Oligopeptides in Organic SolventsCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2010Bao-juan Xin Abstract The use of nanobiocatalysts, with the combination of nanotechnology and biotechnology, is considered as an exciting and rapidly emerging area. The use of iron oxide magnetic nanoparticles, as enzyme immobilization carriers, has drawn great attention because of their unique properties, such as controllable particle size, large surface area, modifiable surface, and easy recovery. In this study, various ,-Fe2O3/Fe3O4 magnetic nanoparticles with immobilized proteases were successfully prepared by three different immobilization strategies including A),direct binding, B),with thiophene as a linker, and C),with triazole as a linker. The oligopeptides syntheses catalyzed by these magnetic nanoparticles (MNPs) with immobilized proteases were systematically studied. Our results show that i),for magnetic nanoparticles immobilized ,-chymotrypsin, both immobilization strategies A and B furnished good reusability for the Z-Tyr-Gly-Gly-OEt synthesis, the MNPs enzymes can be readily used at least five times without significant loss of its catalytic performance: ii),In the case of Z-Asp-Phe-OMe synthesis catalyzed by magnetic nanoparticles immobilized thermolysin, immobilization Strategy,B provided the best recyclability: iii),For the immobilized papain, although Strategy,A or B afforded an immobilized enzyme for the first cycle of Z-Ala-Leu-NHNHPh synthesis in good yield, their subsequent catalytic activity decreased rapidly. In general, the ,-Fe2O3 MNPs were better for use as an immobilization matrix, rather than the Fe3O4 MNPs, owing to their smaller particle size and higher surface area. [source] How Does the Trans,Cis Photoisomerization of Azobenzene Take Place in Organic Solvents?CHEMPHYSCHEM, Issue 5 2010Giustiniano Tiberio Dr. Abstract The trans,cis photoisomerization of azobenzene-containing materials is key to a number of photomechanical applications, but the actual conversion mechanism in condensed phases is still largely unknown. Herein, we study the isomerization in a vacuum and in various solvents via a modified molecular dynamics simulation adopting an ab initio torsion,inversion force field in the ground and excited states, while allowing for electronic transitions and a stochastic decay to the fundamental state. We determine the trans,cis photoisomerization quantum yield and decay times in various solvents (n -hexane, anisole, toluene, ethanol, and ethylene glycol), and obtain results comparable with experimental ones where available. A profound difference between the isomerization mechanism in vacuum and in solution is found, with the often neglected mixed torsional,inversion pathway being the most important in solvents. [source] Antimony-Doped Tin Oxide Nanocrystals: Synthesis and Solubility Behavior in Organic SolventsCHEMPHYSCHEM, Issue 5 2009Rafael O. da Silva Abstract The right mix: SnO2:Sb nanocrystals (NCs) can be solubilized into organic solvents with a suitable solvent/surfactant combination to achieve a stable colloid (see picture). A single synthesis route and different solvent/amphiphilic molecule pairs are used to obtain soluble NC colloids, instead of requiring several syntheses to obtain soluble NCs in different solvents. This work focuses on the nonaqueous synthesis of antimony-doped tin oxide nanocrystals in the size range of 2,6 nm and the investigation of their solubility in organic solvents (CHCl3 and THF) in the presence of amphiphilic molecules (oleic acid and oleylamine). To unravel the underlying processes, a set of molecular dynamics simulations is performed involving the compatibility of oleic acid and oleylamine in mixtures with both CHCl3 and THF. The results show that the method is useful for obtaining the desired oxide, and that the interaction between amphiphilic molecules and solvents can be predicted by molecular dynamics simulations with very good qualitative agreement. [source] Spectroscopic and Electrochemical Evaluation of Salt Effects on Electron-Transfer Equilibria between Donor/Acceptor and Ion-Radical Pairs in Organic SolventsCHEMPHYSCHEM, Issue 16 2008Sergiy V. Rosokha Dr. Abstract Addition of "inert" tetrabutylammonium hexafluorophosphate (Bu4NPF6) to a solution of TMDO/DDQ in dichloromethane (where TMDO=2,2,6,6-tetramethylbenzo[1,2-d;4,5-d]bis[1,3]-dioxole, donor, and DDQ=diclorodicyano-p-benzoquinone, acceptor) is accompanied by drastic changes in the electronic spectrum, which are related to the appearance of the DDQ,. and TMDO+. ion radicals and a decrease in the concentration of the neutral molecules and the charge-transfer complex [TMDO,DDQ]. These changes point to a considerable rise (of about three orders of magnitude) in the apparent electron-transfer equilibrium constant (KET) for this donor/acceptor pair upon increasing the electrolyte concentration from 0 to 0.5,M. Accordingly, the ion-radical fractions and KET values are higher in dichloromethane, at high electrolyte concentrations, than in acetonitrile (where the effect of Bu4NPF6 is less pronounced). Similar trends of the apparent equilibrium constants are observed for the tetramethyl-p-phenylenediamine/tetracyanoethylene pair. Electron-transfer equilibrium constants for both donor/acceptor dyads obtained from spectral measurements are related to those derived from the redox potentials of the reactants. The effects of media variations on the electron-transfer equilibria are discussed within the ion-pairing and ionic-activity frameworks. [source] Organic solvents in CEELECTROPHORESIS, Issue S1 2009Ernst Kenndler Abstract In this contribution some fundamental aspects are discussed serving for a critical reflection and elucidation of the role of organic solvents in CE. The implications of the solvent on the parameters governing peak resolution are discussed based on the concepts describing migration and zone broadening in capillary zone electrophoresis. This discussion includes the solvent-dependent influence of the ionic strength on the mobility. The role of the solvent on the plate number in case of the inevitable diffusional peak dispersion is outlined, and its effect on other peak broadening contributions is briefly examined. This paper also deals with the problems of conductance, applicable voltage and analysis time upon application of organic solvents, and tries to clarify some misunderstandings common in the literature. [source] Study of electromigration effects on a pH boundary during the on-line electrokinetic preconcentration by capillary electrophoresisELECTROPHORESIS, Issue 16 2010ina Vítková Abstract A contribution to the description of electrokinetic effects on the pH boundary formed by sodium borate pH 9.5 and sodium phosphate pH 2.5 electrolytes for on-line preconcentration of weak acids is presented in this article. Simulations of electrokinetic injections together with experimental studies using contactless conductivity detection verified that the preconcentration is induced mainly by dissociation changes of analytes on the pH boundary and transient ITP state. Moreover, a study of the addition of organic solvent to the injection electrolyte was performed with impressive results. Subnanomolar LODs of hydroxybenzoic acids were achieved with 80% of methanol in the injection electrolyte which represents more than 70,000-fold preconcentration in comparison with classical CZE method. [source] Microstructure of microemulsion in MEEKCELECTROPHORESIS, Issue 4 2010Yuhua Cao Abstract The influences of the composition of microemulsion on the microstructure including dimensions and , potentials of microdroplets were measured in details. The average dynamic dimension of microdroplets was measured by dynamic laser light scattering, and , potential was determined to characterize average surface charge density of microdroplets. The experiment results showed that increase of the amount of surfactant resulted in decrease of microdroplet size but almost invariant , potential, which would enlarge migration time of the microdroplet in MEEKC. With increment of cosurfactant concentration, the microdroplet size had an increasing trend, whereas the , potential decreased. Thus, observed migration velocity of microdroplets increased, which made the separation window in MEEKC shortened. Neither dimension nor , potential of microdroplets changed by varying both the type and the amount of the oil phase. Adding organic solvent as modifier to microemulsion did not change the microdroplet size, but lowered , potential. The migration time of microdroplet still became larger, since EOF slowed down owing to organic solvent in capillary. So, besides increment of surfactant concentration, organic additive could also enlarge the separation window. Increase of cosurfactant concentration was beneficial for separation efficiency thanks to the looser structure of swollen microdroplet, and the peak sharpening might compensate for the resolution and peak capacity owing to a narrow separation window. Except the oil phase, tuning the composition of microemulsion would change the microstructure, eventually could be exploited to optimize the resolution and save analysis time in MEEKC. [source] Combined use of supported liquid membrane and solid-phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wineELECTROPHORESIS, Issue 7 2008Sara Almeda Abstract This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20,mL volume of a standard solution at pH,1 or a wine sample at pH,8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1,mL water, pH,11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4,mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1,mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1,mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30,,g/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis. [source] A generic approach to the impurity profiling of drugs using standardised and independent capillary zone electrophoresis methods coupled to electrospray ionisation mass spectrometryELECTROPHORESIS, Issue 9 2005Aurélie Vassort Abstract Three standardised, capillary zone electrophoresis-electrospray ionisation mass spectrometry (CZE-ESI-MS) methods were developed for the analysis of six drug candidates and their respective process-related impurities comprising a total of 22 analytes with a range of functional groups and lipophilicities. The selected backround electrolyte conditions were found to be: 60/40 v/v 10 mM ammonium formate pH 3.5/organic, 60/40 v/v 10 mM ammonium acetate pH 7.0/organic and 10 mM piperidine, pH 10.5, where the organic solvent is 50/50 v/v methanol/acetonitrile. The coaxial sheath flow consisted of either 0.1% v/v formic acid in 50/50 v/v methanol/water, or 10 mM ammonium acetate in 50/50 v/v methanol/water, depending on the mixture being analysed. Factor analysis and informational theory were used to quantify the orthogonality of the methods and predict their complementarities. The three selected CZE-ESI-MS methods allowed the identification of 21 out of 22 of all the drug candidates and their process-related impurities and provided orthogonality with four established high-performance liquid chromatography-mass spectrometry (HPLC-MS) methods. These methodologies therefore form the basis of a generic approach to impurity profiling of pharmaceutical drug candidates and can be applied with little or no analytical method development, thereby offering significant resource and time savings. [source] Microemulsion electrokinetic chromatography of drugs varying in charge and hydrophobicity: I. Impact of parameters on separation performance evaluated by multiple linear regression modelsELECTROPHORESIS, Issue 1 2004Valérie Harang Abstract The separation of anionic, cationic and neutral drugs in microemulsion electrokinetic chromatography (MEEKC) was studied with a statistical experimental design. The concentration of sodium dodecyl sulfate (SDS, surfactant), 1-butanol (co-surfactant) and borate buffer and the factors Brij 35 (surfactant), 2-propanol (organic solvent) and cassette temperature were varied simultaneously, while the parameters pH (9.2), the concentration of octane (oil, 0.8% w/w), the voltage (10 kV) and the dimension of the fused-silica capillary, were kept constant. Eight different model substances were chosen with different hydrophobicities. Two of the analytes were positively charged, two were negatively charged, and the remaining four were neutral or close to neutral at the pH explored. The importance of each parameter on the separation window, the plate height and the retention factor for each of the analytes was studied by means of multiple linear regression (MLR) models. A new response was evaluated for anions, the quotient between the effective mobility in the microemulsion and the effective mobility in the corresponding buffer. Factors affecting selectivity changes were also explored, and it was found that SDS and 2-propanol had the largest effect on selectivity. [source] | |||||||||||||||||||||||||||||||||||||||||||