Home About us Contact
|
Home About us Contact | ||
|
|
||
Efficient Separation (efficient + separation)
Selected AbstractsRepetitive Application of a Fluorous Chiral BINAP,Ru Complex in the Asymmetric Hydrogenation of OlefinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2007Joachim Horn Abstract A trisperfluoroalkylsilyl-modified (S)-BINAP ligand has been prepared and its pertinent Ru complex applied to the asymmetric hydrogenation of olefins. Efficient separation of the Ru catalyst by filtration and its reuse was achieved. Relative to the untagged complex with a Ru-leaching of 300 ppm, leaching into the product was low (1.6,4.9 ppm). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Recycling of nickel,metal hydride batteries.JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2004I: Dissolution, solvent extraction of metals Abstract Nickel,metal hydride batteries contain valuable metallic components and although they are not considered a hazardous waste, recovery of these materials is necessary from an economic point of view. In this work a hydrometallurgical method for the dissolution and separation of the metals from cylindrical nickel,metal hydride rechargeable batteries was investigated. Hydrochloric acid was employed as the leaching agent to dissolve the metals from the batteries. Dissolution of metals was investigated as a function of acid concentration, leaching time and temperature. Suitable conditions for maximum metal dissolution were 3 h leaching with 4.0 mol dm,3 hydrochloric acid solutions at 95 °C. Extraction of 98% of nickel, 100% of cobalt and 99% of rare earth elements was achieved under these conditions. Separation of the rare earths from nickel and cobalt was preliminarily investigated by single batch solvent extraction with 25% bis(2-ethylhexyl)phosphoric acid. Efficient separation via complete extraction of the rare earths was obtained at a pH of approximately 2.5 while leaving nickel and cobalt in the raffinate. A shrinking particle model which can enable, under certain conditions, evaluation of the extent of metal dissolution present in nickel,metal hydride batteries was developed. A proposed electrochemical recovery of nickel and cobalt is also briefly discussed. Copyright © 2004 Society of Chemical Industry [source] Efficient separation of enantiomers by preferential crystallization in two coupled vesselsAICHE JOURNAL, Issue 3 2009Martin Peter Elsner Abstract The focus of this work is to study the enantioseparation of conglomerate forming systems using an innovative configuration for preferential crystallization. Two batch crystallizers are coupled by an exchange of their liquid phases. In each vessel one of the two enantiomers is seeded initially and crystallizes subsequently. Compared with conventional single batch crystallization the exchange of the crystal free liquid phases between two crystallizers leads to an increase of the concentrations of the preferred enantiomers and therefore to an increase of the driving forces for the crystallization. This enhances the productivity of the process compared with the conventional operation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Direct injection horse-urine analysis for the quantification and confirmation of threshold substances for doping control.DRUG TESTING AND ANALYSIS, Issue 8 2009Abstract Levodopa and dopamine have been abused as performance-altering substances in horse racing. Urinary 3-methoxytyramine is used as an indicator of dopaminergic manipulation resulting from dopamine or levodopa administration and is prohibited with a urinary threshold of 4 µg mL,1 (free and conjugated). A simple liquid chromatographic (LC)/mass spectrometric (MS) (LCMS) method was developed and validated for the quantification and identification of 3-methoxytyramine in equine urine. Sample preparation involved enzymatic hydrolysis and protein precipitation. Hydrophilic interaction liquid chromatography (HILIC) was selected as a separation technique that allows effective retention of polar substances like 3-methoxytyramine and efficient separation from matrix compounds. Electrospray ionization (ESI) in positive mode with product ion scan mode was chosen for the detection of the analytes. Quantification of 3-methoxytyramine was performed with fragmentation at low collision energy, resulting in one product ion, while a second run at high collision energy was performed for confirmation (at least three abundant ions). Studies on matrix effects showed ion suppression depending on the horse urine used. To overcome the variability of the results originating from the matrix effects, isotopic labelled internal standard was used and linear regression calibration methodology was applied for the quantitative determination of the analyte. The tested linear range was 1,20 µg mL,1. The relative standard deviations of intra- and inter- assay analysis of 3-methoxytyramine in horse urine were lower than 4.2% and 3.2%, respectively. Overall accuracy (relative percentage error) was less than 6.2%. The method was applied to case samples, demonstrating simplicity, accuracy and selectivity. Copyright © 2009 John Wiley & Sons, Ltd. [source] Nanostructured pillars based on vertically aligned carbon nanotubes as the stationary phase in micro-CECELECTROPHORESIS, Issue 12 2009Ren-Guei Wu Abstract We present a micro-CEC chip carrying out a highly efficient separation of dsDNA fragments through vertically aligned multi-wall carbon nanotubes (MWCNTs) in a microchannel. The vertically aligned MWCNTs were grown directly in the microchannel to form straight nanopillar arrays as ordered and directional chromatographic supports. 1-Pyrenedodecanoic acid was employed for the surface modification of the MWCNTs' stationary phase to adsorb analytes by hydrophobic interactions. This device was used for separating dsDNA fragments of three different lengths (254, 360, and 572,bp), and fluorescence detection was employed to verify the electrokinetic transport in the MWCNT array. The micro-CEC separation of the three compounds was achieved in less than 300,s at a field strength of 66,V/cm due to superior laminar flow patterns and a lower flow resistance resulting from the vertically aligned MWCNTs being used as the stationary phase medium. In addition, a fivefold reduction of band broadening was obtained when the analyte was separated by the chromatographic MWCNT array channel instead of the CE channel. From all of the results, we suggest that an in situ grown and directional MWCNT array can potentially be useful for preparing more diversified forms of stationary phases for vertically efficient chip-based electrochromatography. [source] Co-electroosmotic capillary electrophoresis of basic proteins with 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids as non-covalent coating agents of the fused-silica capillary and additives of the electrolyte solutionELECTROPHORESIS, Issue 11 2009Danilo Corradini Abstract The paper reports the results of a study carried out to evaluate the use of three 1-alkyl-3-methylimidazolium-based ionic liquids as non-covalent coating agents for bare fused-silica capillaries and additives of the electrolyte solutions (BGE) for CE of basic proteins in the co-EOF separation mode. The three ionic liquids are differentiated from each other by the length of the alkyl group on the imidazolium cation, consisting of either an ethyl, butyl or octyl substituent, whereas tetrafluoroborate is the common anionic component of the ionic liquids. Coating the capillary with the ionic liquid resulted in improved peak shape and protein separation, while the EOF was maintained cathodic. This indicates that each ionic liquid is effective at masking the protein interaction sites on the inner surface of the capillary, also when its adsorption onto the capillary wall has not completely neutralized all the negative charges arising from the ionization of the silanol groups and the ionic liquid is not incorporated into the BGE employed for separation. Using the coated capillaries with BGE containing the ionic liquid employed for the coating, at concentration low enough to maintaining the EOF cathodic, both peak shape and protein separation varied to different extents, based on the particular ionic liquid used and its concentration. Fast and efficient separation of the model basic protein mixture in co-electroosmotic CE is obtained with the 1-butyl-3-methylimidazolium tetrafluoroborate coated capillary and 100,mM acetate buffer (pH 4.0) containing 4.4,mM 1-butyl-3-methylimidazolium tetrafluoroborate as the BGE. [source] Development of a new method for analysis of Sudan dyes by pressurized CEC with amperometric detectionELECTROPHORESIS, Issue 11 2007Shaofeng Liu Abstract A new analytical method, pressurized CEC (pCEC) with amperometric detection (AD) using 1.5,,m RP nonporous silica packed columns has been developed for the rapid separation and determination of four Sudan dyes in hot chilli. The influence of several experimental parameters on the retention behavior has been investigated. The electrochemical oxidation of Sudans I,IV separated by pCEC can be reliably monitored with a carbon electrode at +0.95,V (vs. Ag/AgCl). Fast and efficient separation of the analytes was achieved within 7,min by pCEC under the optimum conditions with an ACN/water (95:5%) mobile phase containing formic acid (pH,4.3), 5% acetone and 0.002% triethylamine using a separation voltage of 12,kV. The detection limits for four Sudan dyes ranged from 8.0,×,10,7 to 1.2,×,10,6,mol/L. To evaluate the feasibility and reliability of this method, the proposed pCEC-AD method was further demonstrated with hot chilli samples spiked with Sudan dyes. [source] Separation and recovery of intact gold-virus complex by agarose electrophoresis and electroelution: Application to the purification of cowpea mosaic virus and colloidal gold complexELECTROPHORESIS, Issue 17 2004Carissa M. Soto Abstract Colloidal gold has been coupled to a mutant cowpea mosaic virus (CPMV), which contains 60 cysteine residues on the surface. A purification process was developed to separate the gold-containing viral nanoblocks (VNBs) from the free gold. Agarose electrophoresis was utilized to separate the mixture followed by electroelution of the desired sample to recover the intact virus. Mobility of Au-VNB and free colloidal gold was facilitated by the addition of thioctic acid (TA). 30% of the gold-containing virus was recovered after electroelution as determined by absorbance measurements. Histogram analysis of transmission electron microscopy (TEM) images demonstrated the efficient separation of gold-containing virus from free gold. TEM and scanning electron microscopy (SEM) images indicated that the virus was recovered intact. Monodisperse spherical particles of nominal size of 45 nm were observed under SEM. [source] Improved Synthesis and Isolation of 2,- O -Methyladenosine: Effective and Scalable Enzymatic Separation of 2,/3,- O -Methyladenosine RegioisomersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009Saúl Martínez-Montero Abstract An efficient separation of a mixture of 2,/3,- O -methyladenosine regioisomers (1 + 2; 1:1) has been developed by selective enzymatic acylation using immobilized Pseudomonas cepacia lipase (PSL-C) in combination with acetonoxime levulinate as acyl donor. The 3,-hydroxy group of 2,- O -methyladenosine (1) was acylated with high selectivity (ca. 70,%), whereas an equal amount of 3,- O -methyladenosine (2) in the same solution resulted in minor acylation of 5,-hydroxy group (ca. 8,%). The differential behavior of both regioisomers towards enzymatic acylation allowed to develop a separation protocol. Upon extraction of the acylated products, the 3,- O -methyladenosine was isolated in 81,% yield and 97,% purity from the aqueous layer. Hydrolysis of acylated products in organic layer furnished 2,- O -methyladenosine in 67,% yield and 99,% purity. The separation process was successfully applied to the crude reaction mixture of methylated products (ca. 3:1 of 1/2) on 5-g scale. We also report on the use of methyl p -toluenesulfonate as a safe reagent for 2,- O -methylation of adenosine.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Hydrodynamic considerations on optimal design of a three-phase airlift bioreactor with high solids loadingJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2003Jaroslav Klein Abstract The hydrodynamic study of a three-phase airlift (TPAL) bioreactor with an enlarged gas,liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca-alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal-loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross-sectional area ratio (AD/AR) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry [source] Densitometric determination of zinc bacitracin and nystatin in animal feedJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2008Rade Injac Abstract BACKGROUND: The European Union has forbidden the use of antibiotics as additives in animal feed. Zn-bacitracin (Zn-BC) and nystatin (NYS) were frequently used for their growth-promoting effects and for feed conversion in poultry, pigs and cattle. An HPTLC method has been developed for separating Zn-BC and NYS in the mixture, for routine quality control. RESULTS: The separation was obtained using RP-18 F254S coated HPTLC plates with acetonitrile/methanol (equal volumes):toluene:KH2PO4/KOH (buffer, pH 6.8) = 57:3:40 (v/v/v), adjusted with HCl to pH 8.2, as a mobile phase. The densitograms were monitored at 192, 215 and 305 nm and both antibiotics were assayed at 215 nm. The method was shown to be specific, accurate (recoveries were 98.7 ± 0.5% and 104.8 ± 0.7% for Zn-BC and NYS, respectively), linear over the tested range (correlation coefficients, 0.9982 and 0.9884), and precise (intermediate precision RSD below 2.2% for both analytes) with efficient separation (Rs = 3.5). CONCLUSION: The method was applied for determining Zn-BC and NYS as additives in spiked matrices of commercial animal feedstuffs. According to LOD values for each antibiotic, the minimum detectable amount in feed is 4.5 and 5.5 ppm of Zn-BC and NYS, respectively. Copyright © 2008 Society of Chemical Industry [source] Mycosporine-glutamicol-glucoside: a natural UV-absorbing secondary metabolite of rock-inhabiting microcolonial fungiRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2003Marc Volkmann Microcolonial ascomycetes are known to inhabit bare rock surfaces in cold and hot deserts and thus are habitually exposed to high levels of solar radiation. Several of these stress-tolerant fungal isolates, cultivated in the laboratory under daylight illumination, were studied for the presence of effective UV-radiation protection substances. Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses allowed for efficient separation and structure clarification of two mycosporines. It was demonstrated that both mycosporine-glutamicol-glucoside and mycosporine-glutaminol-glucoside are natural and constitutive secondary metabolites of microcolonial fungi. The function and relation of these substances in the fungal cell are discussed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Separation with zwitterionic hydrophilic interaction liquid chromatography improves protein identification by matrix-assisted laser desorption/ionization-based proteomic analysisBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Atsushi Intoh Abstract Comprehensive proteomic analyses necessitate efficient separation of peptide mixtures for the subsequent identification of proteins by mass spectrometry (MS). However, digestion of proteins extracted from cells and tissues often yields complex peptide mixtures that confound direct comprehensive MS analysis. This study investigated a zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) technique for the peptide separation step, which was verified by subsequent MS analysis. Human serum albumin (HSA) was the model protein used for this analysis. HSA was digested with trypsin and resolved by ZIC-HILIC or conventional strong cation exchange (SCX) prior to MS analysis for peptide identification. Separation with ZIC-HILIC significantly improved the identification of HSA peptides over SCX chromatography. Detailed analyses of the identified peptides revealed that the ZIC-HILIC has better peptide fractionation ability. We further demonstrated that ZIC-HILIC is useful for quantitatively surveying cell surface markers specifically expressed in undifferentiated embryonic stem cells. These results suggested the value of ZIC-HILIC as a novel and efficient separation method for comprehensive and quantitative proteomic analyses. Copyright © 2009 John Wiley & Sons, Ltd. [source] Carbohydrate-Encapsulated Gold Nanoparticles for Rapid Target-Protein Identification and Binding-Epitope MappingCHEMBIOCHEM, Issue 7 2005Yu-Ju Chen Dr. Carbohydrate,lectin recognition plays important roles in cell,cell communication, proliferation, and differentiation. We report here a new approach of using a carbohydrate-encapsulated gold nanoparticle (shown in purple) as an affinity probe for the efficient separation and enrichment of target proteins, and then protein identification and epitope mapping by MALDI-TOF MS. [source] Capillary and microchip electrophoresis in microdialysis: Recent applicationsELECTROPHORESIS, Issue 1 2010Elizabeth Guihen Abstract The theme of this review is to highlight the importance of microscale electrophoretic-based separation systems in microdialysis (,D). The ability of CE and MCE to yield very rapid and highly efficient separations using just nanolitre volumes of microdialysate samples will also be discussed. Recent advances in this area will be highlighted, by illustration of some exciting new applications while the need for further innovation will be covered. The first section briefly introduces the concept of ,D sampling coupled with electrophoresis-based separation and the inherent advantages of this approach. The following section highlights some specific applications of CE separations in the detection of important biomarkers such as low-molecular-weight neurotransmitters, amino acids, and other molecules that are frequently encountered in ,D. Various detection modes in CE are outlined and some of the advantages and drawbacks thereof are discussed. The last section introduces the concepts of micro-total analysis systems and the coupling of MCE and ,D. Some of the latest innovations will be illustrated. The concluding section reflects on the future of this important chemical alliance between ,D and CE/MCE. [source] Sieving mechanisms in polymeric matricesELECTROPHORESIS, Issue 3 2003Anna Sartori Abstract A critical review of the existing theoretical models and experimental evidences for sieving mechanisms during separation of macromolecules, paying particular attention to capillary electrophoresis applications is presented. Gel models (Ogston and reptation) have been successfully applied to highly entangled polymer solutions, where fast and efficient separations can occur. In order to account for the DNA/polymers collision-interaction mechanisms during separation in dilute solutions , characterized by a poorer resolution ,, approximated analytical models have been developed. An insight in the mechanism regulating the intermediate case of moderately entangled polymer solutions, for low fields and concentrations of small multiples of the overlap concentration c*, is given by the constraint release approach. This model proposes an upper limit of size separation, increasing with matrix concentration and molecular mass. Finally, the coupling between the reptative motion of the analytes and the effect of matrix constraint release very likely plays a fundamental role in the separation mechanism and requires therefore further and deeper investigation, both theoretically and experimentally. [source] An initial assessment of the use of gradient elution in microemulsion and micellar liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2004Simon M. Bryant Abstract Novel microemulsion and micellar HPLC separations have been achieved using gradient elution and columns packed with reverse phase material. Initial attempts at gradient microemulsion liquid chromatography proved impossible on use of a microemulsion successfully used in capillary electrophoresis. Optimisation of the microemulsion composition allowed the generation of stable microemulsions to achieve separations in HPLC. The novel use of organic-solvent micellar chromatography in gradient elution mode was shown to give efficient separations. A range of efficient separations of pharmaceuticals and related impurities were obtained. Acidic, basic, and neutral solutes were resolved covering a wide range of water solubilities and polarities. Elution times were in the order of 4,15 minutes. Separations were briefly compared to those accomplished with a micellar HPLC system. It is proposed that gradient elution in both microemulsion and micellar HPLC can be regarded as a highly successful means of achieving resolution of complex mixtures and should be considered for routine analysis and further investigation. [source] Use of activated graphitized carbon chips for liquid chromatography/mass spectrometric and tandem mass spectrometric analysis of tryptic glycopeptidesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2009William R. Alley Jr. Protein glycosylation has a significant medical importance as changes in glycosylation patterns have been associated with a number of diseases. Therefore, monitoring potential changes in glycan profiles, and the microheterogeneities associated with glycosylation sites, are becoming increasingly important in the search for disease biomarkers. Highly efficient separations and sensitive methods must be developed to effectively monitor changes in the glycoproteome. These methods must not discriminate against hydrophobic or hydrophilic analytes. The use of activated graphitized carbon as a desalting media and a stationary phase for the purification and the separation of glycans, and as a stationary phase for the separation of small glycopeptides, has previously been reported. Here, we describe the use of activated graphitized carbon as a stationary phase for the separation of hydrophilic tryptic glycopeptides, employing a chip-based liquid chromatographic (LC) system. The capabilities of both activated graphitized carbon and C18 LC chips for the characterization of the glycopeptides appeared to be comparable. Adequate retention time reproducibility was achieved for both packing types in the chip format. However, hydrophilic glycopeptides were preferentially retained on the activated graphitized carbon chip, thus allowing the identification of hydrophilic glycopeptides which were not effectively retained on C18 chips. On the other hand, hydrophobic glycopeptides were better retained on C18 chips. Characterization of the glycosylation sites of glycoproteins possessing both hydrophilic and hydrophobic glycopeptides is comprehensively achieved using both media. This is feasible considering the limited amount of sample required per analysis (<1,pmol). The performance of both media also appeared comparable when analyzing a four-protein mixture. Similar sequence coverage and MASCOT ion scores were observed for all proteins when using either stationary phase. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||