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Acetonitrile
Terms modified by Acetonitrile Selected AbstractsAn improved validated ultra high pressure liquid chromatography method for separation of tacrolimus impurities and its tautomersDRUG TESTING AND ANALYSIS, Issue 3 2010Acharya Subasranjan Abstract A selective, specific and sensitive ultra high pressure liquid chromatography (UHPLC) method was developed for determination of tacrolimus degradation products and tautomers in the preparation of pharmaceuticals. The chromatographic separation was performed on Waters ACQUITY UPLC system and BEH C8 column using gradient elution of mobile phase A (90:10 v/v of 0.1% v/v triflouroacetic acid solution and Acetonitrile) and mobile phase B (90:10 v/v acetonitrile and water) at a flow rate of 0.6 mL min,1. Ultraviolet detection was performed at 210 nm. Tacrolimus, tautomers and impurities were chromatographed with a total run time of 25 min. Calibration showed that the response of impurity was a linear function of concentration over the range 0.3,6 µg mL,1 (r2 , 0.999) and the method was validated over this range for precision, intermediate precision, accuracy, linearity and specificity. For precision study, percentage relative standard deviation of each impurity was < 15% (n = 6). The method was found to be precise, accurate, linear and specific. The proposed method was successfully employed for estimation of tacrolimus impurities in pharmaceutical preparations. Copyright © 2010 John Wiley & Sons, Ltd. [source] Ligand-Exchange Processes on Solvated Lithium Cations: Acetonitrile and Hydrogen Cyanide,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Ewa Pasgreta Abstract Solutions of LiClO4 in solvent mixtures of acetonitrile and water, or acetonitrile and nitromethane, were studied by 7Li NMR spectroscopy. Measured chemical shifts indicate that the Li+ cation is coordinated by four acetonitrile molecules. In the binary water/acetonitrile mixture, water coordinates more strongly to Li+ than acetonitrile such that addition of water immediately leads to the formation of [Li(H2O)4]+. The solvent-exchange mechanism for [Li(L)4]+ (L = CH3CN and HCN) was studied by using DFT calculations (RB3LYP/6-311+G**). This process was found to follow a limiting associative mechanism involving the formation of relatively stable five-coordinate intermediates. The suggested mechanisms are discussed with reference to available experimental and theoretical data. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Basicity of Guanidines with Heteroalkyl Side Chains in AcetonitrileEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 30 2008Mirjana Eckert-Maksi Abstract The pKa values of seven novel guanidine derivatives, six of them possessing heteroalkyl substituents capable of forming intramolecular hydrogen bonds, were determined in acetonitrile (MeCN) by using the UV/Vis spectrophotometric titration method. The obtained pKa values range from 24.7 to 27.2. The most basic among the studied guanidines was found to be by ca. 4 pKa units more basic than thewell-known superbase N1,N1,N3,N3 -tetramethylguanidine (TMG). The trends in the changes in the measured pKa values were compared with the experimental (determined by the extended kinetic method) and theoretical [B3LYP/6-311+G(2df,p)//B3LYP/6-31G(d)] gas-phase proton affinities. It was shown that basicity ordering of the bases with dimethylaminopropyl substituents in acetonitrile follows the trend encountered in the gas phase. However, this is not the case for the methoxypropyl-substituted guanidines indicating that in these molecules formation of the intramolecular hydrogen bonds is to large extent hindered due to solvation by acetonitrile.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Two-phase flow electrosynthesis: Comparing N -octyl-2-pyrrolidone,aqueous and acetonitrile,aqueous three-phase boundary reactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2009Stuart M. MacDonald Abstract A microfluidic double channel device is employed to study reactions at flowing liquid,liquid junctions in contact with a boron-doped diamond (BDD) working electrode. The rectangular flow cell is calibrated for both single-phase liquid flow and biphasic liquid,liquid flow for the case of (i) the immiscible N -octyl-2-pyrrolidone (NOP),aqueous electrolyte system and (ii) the immiscible acetonitrile,aqueous electrolyte system. The influence of flow speed and liquid viscosity on the position of the phase boundary and mass transport-controlled limiting currents are examined. In contrast to the NOP,aqueous electrolyte case, the acetonitrile,aqueous electrolyte system is shown to behave close to ideal without ,undercutting' of the organic phase under the aqueous phase. The limiting current for three-phase boundary reactions is only weakly dependent on flow rate but directly proportional to the concentration and the diffusion coefficient in the organic phase. Acetonitrile as a commonly employed synthetic solvent is shown here to allow effective three-phase boundary processes to occur due to a lower viscosity enabling faster diffusion. N -butylferrocene is shown to be oxidised at the acetonitrile,aqueous electrolyte interface about 12 times faster when compared with the same process at the NOP,aqueous electrolyte interface. Conditions suitable for clean two-phase electrosynthetic processes without intentionally added supporting electrolyte in the organic phase are proposed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Photophysics and Photochemistry of z -Chlorprothixene in Acetonitrile,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Luis E. Piñero Chlorprothixene (CPTX, Taractan®) is a low potency antipsychotic mainly used for the treatment of psychotic disorders (e.g. schizophrenia) and acute mania occurring as part of bipolar disorders. As in the case of other numerous drugs used in the treatment of psychiatric disorders, CPTX presents geometric isomerism. Therefore, in vitro irradiation induces a rapid Z/E isomerization, which can affect its pharmacokinetic properties. This photoisomerization is not dependent on the oxygen concentration. The Z/E quantum yields determined for zCPTX in acetonitrile are 0.22 and 0.21 in anaerobic and aerobic environments, respectively. In the presence of water, both isomers decompose to produce 2-chlorothioxanthone (CTX) after prolonged irradiation. This process strongly depends on the water concentration and the irradiation time, i.e. it is autocatalyzed by the CTX through a triplet-energy transfer mechanism. The protonation state of the terminal amino group, on the other hand, has no effect on the isomerization process, but inhibits the formation of CTX. These results indicate that the phototoxicity of zCPTX is somehow affected by the formation of CTX. [source] Assessment of acetone as an alternative to acetonitrile in peptide analysis by liquid chromatography/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2009Ria Fritz Acetonitrile as a solvent used in liquid chromatography/mass spectrometry (LC/MS) of peptides and proteins is a relatively toxic solvent (LD50 oral; rat; 2,460,mg/kg) compared to alternatives like methanol (LD50 oral; rat; 5,628,mg/kg) and acetone (LD50 oral; rat; 5,800,mg/kg). Strategies to minimize its consumption in LC are either to reduce the inner diameter of the column or replace acetonitrile with a suitable alternative. Methanol is often recommended to replace acetonitrile in peptide analysis. In this study however, the main focus lies on another alternative solvent for LC/MS of peptides; acetone. A number of model proteins were tryptically digested and the peptide solutions were analyzed on a linear trap quadrupole (LTQ) mass spectrometer. The performances of acetonitrile, methanol and acetone were compared according to the quality of the chromatograms obtained and identification of the peptides using the BioWorksÔ software developed by Thermo Scientific. In accordance to the elutropic series, acetone was found to significantly reduce the retention times of peptides separated by C18 column material with regard to acetonitrile while methanol led to increased retention times. Acetone was the superior solvent to methanol for most of the tested model proteins reaching similar sequence coverage and numbers of identified peptides as acetonitrile. We therefore propose acetone as an alternative to acetonitrile in LC/MS of peptides. Copyright © 2009 John Wiley & Sons, Ltd. [source] Analysis of exhaled breath from smokers, passive smokers and non-smokers by solid-phase microextraction gas chromatography/mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 5 2009Bogus, aw Buszewski Abstract In this study, 38 samples of expired air were collected and analyzed from 20 non-smoking volunteers, four passive smokers and 14 smokers (21 women and 17 men). Measurements were carried out using solid-phase microextraction (SPME) as an isolation and preconcentration technique. The determination and identification were accomplished by gas chromatography coupled with mass spectrometry (GC/MS). Our data showed that ca 32% of all identified compounds in the breath of healthy non-smokers were saturated hydrocarbons. In the breath of smoking and passive smoking volunteers hydrocarbons were predominant, but also present were more exogenous analytes such as furan, acetonitrile and benzene than in the breath of non-smokers. Acetonitrile, furan, 3-methylfuran, 2,5-dimethylfuran, 2-butanone, octane and decane were identified in breath of smoking and passive smoking persons. Copyright © 2008 John Wiley & Sons, Ltd. [source] Salting-out assisted liquid/liquid extraction with acetonitrile: a new high throughput sample preparation technique for good laboratory practice bioanalysis using liquid chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Jun Zhang Abstract Acetonitrile, an organic solvent miscible with aqueous phase, has seen thousands of publications in the literature as an efficient deproteinization reagent. The use of acetonitrile for liquid,liquid extraction (LLE), however, has seen very limited application due to its miscibility with aqueous phase. The interest in LLE with acetonitrile has been pursued and reported in the literature by significantly lowering the temperature of the mixture or increasing the salt concentration in the mixture of acetonitrile and aqueous phase, resulting in the separation of the acetonitrile phase from aqueous phase, as observed in conventional LLE. However, very limited application of these methods has been reported. The throughput was limited. In this report, we report a new sample preparation technique, salting-out assisted liquid,liquid extraction with acetonitrile, for high-thoughput good laboratory practice sample analysis using LCMS, Two compounds from an approved drug, Kaletra®, were used to demonstrate the extractability of drugs from human plasma matrix. Magnesium sulfate was used as the salting-out reagent. Extracts were diluted and then injected into a reversed phase LC-MS/MS system directly. One 96-well plate was extracted with this new approach to evaluate multiple parameters of a good laboratory practice analytical method. Results indicate that the method is rapid, reliable and suitable for regulated bioanalysis. With minimal modification, this approach has been used for high-throughput good laboratory practice analysis of a number of compounds under development at Abbott. Copyright © 2008 John Wiley & Sons, Ltd. [source] Influence of water-miscible organic solvents on kinetics and enantioselectivity of the (R,-specific alcohol dehydrogenase from Lactobacillus brevisBIOTECHNOLOGY JOURNAL, Issue 5 2006Jan Schumacher Abstract Using the organic solvents acetonitrile and 1,4-dioxane as water-miscible additives for the alcohol dehydrogenase (ADH)-catalyzed reduction of butan-2-one, we investigated the influence of the solvents on enzyme reaction behavior and enantioselectivity. The NADP+ -dependent (R,-selective ADH from Lactobacillus brevis (ADH-LB) was chosen as biocatalyst. For cofactor regeneration, the substrate-coupled approach using propan-2-ol as co-substrate was applied. Acetonitrile and 1,4-dioxane were tested from mole fraction 0.015 up to 0.1. Initial rate experiments revealed a complex kinetic behavior with enzyme activation caused by the substrate butan-2-one, and increasing KM values with increasing solvent concentration. Furthermore, these experiments showed an enhancement of the enantioselectivity for (R,-butan-2-ol from 37% enantiomeric excess (ee) in pure phosphate buffer up to 43% ee in the presence of 0.1 mol fraction acetonitrile. Finally, the influence of the co-solvents on water activity of the reaction mixture and on enzyme stability was investigated. [source] ChemInform Abstract: Nickel/Lewis Acid-Catalyzed Carbocyanation of Alkynes Using Acetonitrile and Substituted Acetonitriles.CHEMINFORM, Issue 42 2010Akira Yada Abstract The scope and limitations of the carbocyanation reaction of a variety of alkynes with nitriles (I) and (V) are reported (40 examples). [source] ChemInform Abstract: Catalytic Enantioselective Mannich-Type Reaction with ,-Phenyl Sulfonyl Acetonitrile.CHEMINFORM, Issue 40 2010Pedro B. Gonzalez Abstract Two convenient methods to prepare enantioenriched ,-unsubstituted ,-amino nitriles are reported. [source] ChemInform Abstract: Three-Component Reaction of 5,5-Dimethylcyclohexane-1,3-dione, Aromatic Aldehydes, and Acetonitrile in the Presence of Chlorosulfonic Acid Forming N-[(2-Hydroxy-4-4-dimethyl-6-oxocyclohexene-1-yl)-aryl-methyl] -acetamides.CHEMINFORM, Issue 15 2010Mohammad Anary-Abbasinejad 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] ChemInform Abstract: BF3·Et2O-Induced Decomposition of Ethyl 2-Diazo-3-hydroxy-3,3-diarylpropanoates in Acetonitrile: A Novel Approach to 2,3-Diaryl ,-Enamino Ester Derivatives.CHEMINFORM, Issue 37 2009Antimo Gioiello 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] ChemInform Abstract: Synthesis of Arylbromides from Arenes and N-Bromosuccinimide (NBS) in Acetonitrile , A Convenient Method for Aromatic Bromination.CHEMINFORM, Issue 34 2009Eli Zysman-Colman 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] ChemInform Abstract: Cyanation of Adamantane and Diamantane with Acetonitrile and Tetrabromomethane in the Presence of Mo(CO)6.CHEMINFORM, Issue 5 2009R. I. Khusnutdinov 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] Copper Nitrate Trihydrate Catalyzed Efficient Synthesis of Bis(indolyl)methanes in Acetonitrile at Room Temperature.CHEMINFORM, Issue 48 2007Aayesha Nasreen 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] An Unusual Oxidation,Dealkylation of 3,4-Dihydropyrimidin-2(1H)-ones Mediated by Co(NO3) 2×6H2O/K2S2O8 in Aqueous Acetonitrile.CHEMINFORM, Issue 21 2007Pachaiyappan Shanmugam 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] An Efficient Deprotection of Dithioacetals to Carbonyls Using Oxone,KBr in Aqueous Acetonitrile.CHEMINFORM, Issue 12 2007U. V. Desai 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] The Crystal and Molecular Structure of Bis(tetramethylammonium) Pentachlorooxomolybdate(V)-Acetonitrile(1:1).CHEMINFORM, Issue 42 2005S. A. Seyedsadjadi Abstract For Abstract see ChemInform Abstract in Full Text. [source] Efficient Synthesis of ,,,-Epoxy Carbonyl Compounds in Acetonitrile: Darzens Condensation of Aromatic Aldehydes with Ethyl Chloroacetate.CHEMINFORM, Issue 51 2004Zong-Ting Wang Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Cerium(III) Chloride Promoted Highly Regioselective Ring Opening of Epoxides and Aziridines Using NaN3 in Acetonitrile: A Facile Synthesis of 1,2-Azidoalcohols and 1,2-Azidoamines.CHEMINFORM, Issue 25 2002Gowravaram Sabitha 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] ChemInform Abstract: The Orientation of the Re2Cl82- Ions in (PPh4)2[Re2Cl8]×2L (L = Acetonitrile, Dichloromethane).CHEMINFORM, Issue 34 2001Andrea Noll 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] ChemInform Abstract: A Highly Efficient, Mild, and Selective Cleavage of ,-Methoxyethoxymethyl (MEM) Ethers by Cerium(III) Chloride in Acetonitrile.CHEMINFORM, Issue 32 2001Gowravaram Sabitha 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] ChemInform Abstract: Reduction of Acetals with Samarium Diiodide in Acetonitrile in the Presence of Lewis Acids.CHEMINFORM, Issue 31 2001Munetaka Kunishima 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] ChemInform Abstract: Kinetics and Mechanism of the Aminolysis of Aryl Phenyldithioacetates in Acetonitrile.CHEMINFORM, Issue 11 2001Hyuck Keun Oh 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] Solubilizing Sodium Fluoride in Acetonitrile: Synthesis, Molecular Structure, and Complexation Behavior of Bis(organostannyl)methyl-Substituted Crown Ethers,CHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2007Gregor Reeske Dr. Abstract The synthesis of the crown-ether-substituted bis(organostannyl)methanes Ph3SnCH2Sn(Ph2)-CH2 -[16]crown-5 (1) and Ph2ISnCH2Sn(I)(Ph)-CH2 -[16]crown-5 (2) is reported. Both compounds have been characterized by elemental analyses, 1H, 13C, 19F, and 119Sn,NMR spectroscopy, and in the case of compound 2 also by electrospray ionization mass spectrometry. Single-crystal X-ray diffraction analysis revealed for the aqua complex 2,H2O trigonal,bipyramidal-configured tin atoms with intramolecular Sn(1)O(1) and Sn(2)O(1W) distances of 2.555(2) and 2.440(3),Å, respectively. The water molecule is trapped in a sandwich-like fashion between the crown ether oxygen atoms O(2) and O(4) and the Sn(2) atom. NMR spectroscopy unambiguously proved the ability of compound 2 in acetonitrile to overcome the high lattice energy of sodium fluoride and to complex the latter under charge separation. [source] Water as a Building Block in Solid-State Acetonitrile,Pyrogallol[4]arene Assemblies: Structural InvestigationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2007Scott Abstract Under various conditions, water molecules dramatically affect a number of solid-state C -alkylpyrogallol[4]arene assemblies. In the absence of water, hydrogen-bonded hexameric capsules are formed for the C -butyl, pentyl, hexyl, and heptyl pyrogallol[4]arenes. Introduction of water to acetonitrile solutions containing C -propyl,C -octylpyrogallol[4]arenes resulted in the formation of markedly different bilayer structures and the structural identification of two new dimer-type motifs. [source] Two-photon Dissociation Study of Carbon Disulfide in Acetonitrile at 266 nmCHINESE JOURNAL OF CHEMISTRY, Issue 1 2006Hao-Jie Fang Abstract Using laser flash photolysis/transient absorption technique for the study of two photon photodissociation of carbon disulfide in acetonitrile solution at 266 nm, the transient UV-Vis absorption spectrum of Rydberg state CS2 (6s,g) within 240,370 nm and subsequent dissociation product CS (,3,) with the maximum absorption at 260 nm were directly observed. The lifetime of CS (,3,) in the nitrogen and oxygen saturated solution is also studied in our experiment. [source] An improved validated ultra high pressure liquid chromatography method for separation of tacrolimus impurities and its tautomersDRUG TESTING AND ANALYSIS, Issue 3 2010Acharya Subasranjan Abstract A selective, specific and sensitive ultra high pressure liquid chromatography (UHPLC) method was developed for determination of tacrolimus degradation products and tautomers in the preparation of pharmaceuticals. The chromatographic separation was performed on Waters ACQUITY UPLC system and BEH C8 column using gradient elution of mobile phase A (90:10 v/v of 0.1% v/v triflouroacetic acid solution and Acetonitrile) and mobile phase B (90:10 v/v acetonitrile and water) at a flow rate of 0.6 mL min,1. Ultraviolet detection was performed at 210 nm. Tacrolimus, tautomers and impurities were chromatographed with a total run time of 25 min. Calibration showed that the response of impurity was a linear function of concentration over the range 0.3,6 µg mL,1 (r2 , 0.999) and the method was validated over this range for precision, intermediate precision, accuracy, linearity and specificity. For precision study, percentage relative standard deviation of each impurity was < 15% (n = 6). The method was found to be precise, accurate, linear and specific. The proposed method was successfully employed for estimation of tacrolimus impurities in pharmaceutical preparations. Copyright © 2010 John Wiley & Sons, Ltd. [source] Organic Phase PPO Biosensors Prepared by Multilayer Deposition of Enzyme and Alginate Through Avidin-Biotin InteractionsELECTROANALYSIS, Issue 24 2004S. Cosnier Abstract Films of electrogenerated polypyrrole and hydrophilic alginate, both functionalized with biotin moieties, were used to allow for the transfer of polyphenol oxidase activity in organic media. Enzyme electrodes, based on multilayered structures, were protected at the molecular level by the affinity binding of alginate as a hydrophilic additive, and were then transferred into chlorobenzene, dichloromethane, chloroform, ethyl acetate or acetonitrile. The biosensor performance for the detection of catechol at ,0.2,V was investigated, highlighting the main influence of the hydrophobicity of the solvent and, to a lesser extent, the dielectric constant. The effect of the substrate hydrophobicity on the biosensor response was examined in chlorobenzene. [source] | ||||||||||||||||||||||||||||||||||||||||