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PubMed2005

Two-dimensional liquid chromatography normal-phase and reversed-phase separation of (co)oligomers.

Many samples contain compounds with various numbers of two or more regular structural groups. Such "multidimensional" samples (according to the Giddings' notation) are best separated in orthogonal chromatographic systems with different selectivities for the individual repeat structural groups, described by separation factors. Correlations between the repeat group selectivities characterize the degree of orthogonality and suitability of chromatographic systems for two-dimensional (2D) separations of two-dimensional samples. The range of the structural units in that can be resolved in a given time can be predicted on the basis of a model describing the repeat group selectivity in the first- and second-dimension systems. Two-dimensional liquid chromatographic system combining reversed-phase (RP) mode in the first dimension and normal-phase (NP) mode in the second dimension were studied with respect to the possibilities of in-line fraction transfer between the two modes. Hydrophilic interaction liquid chromatography (HILIC) with an aminopropyl silica column (APS) is more resistant than classical non-aqueous NP systems against adsorbent desactivation with aqueous solvents transferred in the fractions from the first, RP dimension to the second dimension. Hence, HILIC is useful as a second-dimension separation system for comprehensive RP-NP LCxLC. A comprehensive 2D RP-NP HPLC method was developed for comprehensive 2D separation of ethylene oxide-propylene oxide (EO-PO) (co)oligomers. The first-dimension RP system employed a 120 min gradient of acetonitrile in water on a C18 microbore column at the flow-rate of 10 microL/min. In the second dimension, isocratic HILIC NP with ethanol-dichloromethane-water mobile phase on an aminopropyl silica column at 0.5 mL/min was used. Ten microliter fractions were transferred from the RP to the HILIC NP system at 1 min switching valve cycle frequency.

Acetonitriles↗
PubMed2006

Separation of atropisomers of anti-hepatitis drug dimethyl diphenyl bicarboxylate analogues by capillary electrophoresis with vancomycin as the chiral selector.

Separation of atropisomers of analogues of the anti-hepatitis drug dimethyl diphenyl bicarboxylate (DDB) by capillary electrophoresis with vancomycin as the chiral selector is described. Among several tested chiral selectors, including various cyclodextrin derivatives as well as vancomycin, only the latter displayed the enantioselectivity to the studied atropisomers. However, relatively poor separation efficiency was obtained due to the adsorption of vancomycin on the capillary wall. This problem was overcome by modifying the capillary wall with a polycationic electrolyte named hexadimethrine bromide (HDB) to produce a positively charged coating, which minimized the adsorption of vancomycin on the capillary wall by electrostatic repulsion. Moreover, the positively charged coating could shorten the separation time by reversing the EOF because the reversed EOF migrated to the same direction as the negatively charged analyte. Effects of buffer pH, vancomycin and buffer concentrations and applied voltage on the separation were investigated and the optimal conditions were established as follows: 40 mM Tris-phosphate buffer (pH 6.0) containing 6.0 mM vancomycin and 0.001% HDB. Baseline separation of three racemic DDB analogues was obtained within 12 min under the optimal conditions.

Antiviral Agents↗
PubMed2006

Separation method based on affinity reaction between magnetic and nonmagnetic particles for the analysis of particles and biomolecules.

A separation method is reported for particle and biochemical analysis based on affinity interactions between particle surfaces under magnetic field. In this method, magnetic particles with immunoglobulin G (IgG) or streptavidin on the surface are flowed through a separation channel to form a deposition matrix for selectively capturing nonmagnetic analytes with protein A or biotin on the surface due to specific antigen (Ag)--antibody (Ab) interactions. This separation method was demonstrated using model reactions of IgG--protein A and streptavidin-biotin on particle surface. The features of this new separation method are (1) the deposited Ag-Ab complex can be examined and further analyzed under the microscope, (2) a kinetic study of complex binding is possible, and (3) the predeposited matrix can be formed selectively and changed easily. The detection limits were about 10(-11) g. The running time was less than 10 min. The selectivities of studied particles were 94% higher than those of label-controlled particles. This method extends the applications of analytical magnetapheresis to nonmagnetic particles. Preliminary study shows that this separation method has a great potential to provide a simple, fast, and selective analysis for particles, blood cells, and immunoassay related applications.

Biotin↗
PubMed2006

Preparative separation of vitexin and isovitexin from pigeonpea extracts with macroporous resins.

Vitexin and isovitexin are a pair of isomeric compounds known as the major constituents in pigeonpea leaves and possess various pharmacological activities. In the present study, the preparative separation of vitexin and isovitexin with macroporous resins (Nankai Hecheng S & T, Tianjin, China) was studied. The performance and adsorption characteristics of eight macroporous resins including ADS-5, ADS-7, ADS-8, ADS-11, ADS-17, ADS-21, ADS-31 and ADS-F8 have been evaluated. The research results indicate that ADS-5 resin is most appropriate for the separation of vitexin and isovitexin. Langmuir and Freundlich isotherms were used to describe the interactions between solutes and resin at different temperatures, and the equilibrium experimental data were well fitted to the two isotherms. Column packed with ADS-5 resin was used to perform dynamic adsorption and desorption tests to optimize the separation process. The optimum parameters for adsorption were as follows: the concentration of vitexin and isovitexin in sample solution: 0.22 and 0.40mg/mL, respectively, processing volume: 3 BV, flow rate: 1mL/min, pH 4, temperature: 25 degrees C; for desorption: ethanol-water (40:60, v/v), 5 BV as an eluent, flow rate: 1mL/min. After one run treatment with ADS-5 resin, the contents of vitexin and isovitexin were increased 4.07-fold and 11.52-fold from 0.86%, 1.53% to 3.50% and 17.63%, the recovery yields were 65.03% and 73.99%, respectively. In conclusion, the preparative separation of vitexin and isovitexin can be easily and effectively achieved via adsorption and desorption on ADS-5 resin, and the method can be referenced for the separation of other flavone C-glucosides from herbal materials.

Adsorption↗
PubMed2006

Free flow isotachophoresis in an injection moulded miniaturised separation chamber with integrated electrodes.

An injection moulded free flow isotachophoresis (FFITP) microdevice with integrated carbon fibre loaded electrodes with a separation chamber of 36.4mm wide, 28.7 mm long and 100 microm deep is presented. The microdevice was completely fabricated by injection moulding in carbon fibre loaded polystyrene for the electrodes and crystal polystyrene for the remainder of the chip and was bonded together using ultrasonic welding. Two injection moulded electrode designs were compared, one with the electrode surface level with the separation chamber and one with a recessed electrode. Separations of two anionic dyes, 0.2mM each of amaranth and acid green and separations of 0.2mM each of amaranth, bromophenol blue and glutamate were performed on the microdevice. Flow rates of 1.25 ml min(-1) for the leading and terminating electrolytes were used and a flow rate of 0.63 ml min(-1) for the sample. Electric fields of up to 370 V cm(-1) were applied across the separation chamber. Joule heating was not found to be significant although out-gassing was observed at drive currents greater than 3 mA.

Electrodes↗
PubMed2007

Separation of solanesol in tobacco leaves extract by slow rotary counter-current chromatography using a novel non-aqueous two-phase solvent system.

Non-aqueous solvent system composed of sunflower oil-ethanol was found to be suitable for the separation of lower polarity components. Employing this solvent system, 3 g of tobacco leaves extract containing 15% solanesol was separated using a slow rotary counter-current chromatograph equipped with an 1100 mL column made of 5.7 mm I.D. convoluted PTFE tube. The separation yielded 1.5 g of yellow oily product in which solanesol occupied 26.8% determined by HPLC. The tobacco tar and other main impurities in the tobacco leaves extract were removed after slow rotary counter-current chromatographic separation. The separation processing may be developed as a technique for producing a solanesol product with food grade.

Chromatography, Thin Layer↗
PubMed2003

Enzymatic digestion--a safe and rapid technique for individual separation of Macrobrachium rosenbergii embryos for cryopreservation studies.

A new, safe, and rapid technique for the individual separation of the embryos of giant freshwater prawn Macrobrachium rosenbergii de Man is described. Two protease enzymes, e.g., trypsin and collagenase were used. Embryos in the advanced stage of development (gray embryos with eyespot and heart beat) were selected for the study. Treatment with collagenase and trypsin at respective concentrations of 0.05 and 0.25% for 30 min resulted in 100% separation of 35-40 mg of embryonic mass (approximately 180 embryos). A chelating agent, EDTA (ethylenediaminetetraacetic acid disodium salt: dihydrate) at 400 mg l(-1) enhanced the activity of trypsin. Trypsin and collagenase, when used together, were found to act synergistically. The separated embryos revealed no morphological injury when observed under the microscope. Further, in vitro hatching of the separated embryos was successful indicating that the present technique is safe and effective in achieving individual separation of prawn embryos.

Animals↗
PubMed2006

Factors influencing the electrospray intrasource separation and selective ionization of glycerophospholipids.

The external electric field induces a separation of cations from negative electrolyte ions in the infusate while differential ionization of molecular species that possess differential electrical propensities can be induced in either the positive- or negative-ion mode during the electrospray ionization process. These physical and electrical processes that occur in the electrospray ion source have been used to selectively ionize lipid classes possessing different electrical propensities that are now known as "intrasource separation and selective ionization". However, the chemical principles underlying charge-dependent alterations in ionization efficiencies responsible for the selective ionization of lipid classes are not known with certainty. Herein, we examined the multiple factors that contribute to intrasource separation and selective ionization of lipid classes under optimal instrumental conditions. We demonstrated that many different lipid classes could be selectively ionized in the ion source and that intrasource resolution of distinct molecular constituents was independent of lipid concentration, flow rate, and residual ions under most experimental conditions. Moreover, the presence of alkaline conditions facilitates the selective ionization of many lipid classes through a mechanism independent of the design of the ESI ion source. Collectively, this study provides an empirical foundation for understanding the chemical mechanisms underlying intrasource separation and selective ionization of lipid classes that can potentially be used for global analysis of cellular lipidomes without the need for chromatographic separation.

Algorithms↗
PubMed2004

Membrane separations using molecularly imprinted polymers.

This review presents an overview on the promising field of molecularly imprinted membranes (MIM). The focus is onto the separation of molecules in liquid mixtures via membrane transport selectivity. First, the status of synthetic membranes and membrane separation technology is briefly summarized, emphasizing the need for novel membranes with higher selectivities. Innovative principles for the preparation of membranes with improved or novel functionality include self-assembly or supramolecular aggregation as well as the use of templates. Based on a detailed analysis of the literature, the main established preparation methods for MIM are outlined: simultaneous membrane formation and imprinting, or preparation of imprinted composite membranes. Then, the separation capability of MIM is discussed for two different types, as a function of their barrier structure. Microporous MIM can continuously separate mixtures based on facilitated diffusion of the template, or they can change their permeability in the presence of the template ("gate effect"). Macroporous MIM can be developed towards molecule-specific membrane adsorbers. Emerging further combinations of molecularly imprinted polymers (MIPs), especially MIP nanoparticles or microgels, with membranes and membrane processes are briefly outlined as well. Finally, the application potential for advanced MIM separation technologies is summarized.

Membranes, Artificial↗
PubMed2005

Multidimensional separation of peptides for effective proteomic analysis.

Current solution based proteomic analysis methods are generally based on enzymatic digestion of a protein mixture followed by separation using multidimensional liquid chromatography and/or electrophoresis where peptide identification is typically accomplished by tandem mass spectrometry (MS/MS). It is generally accepted that no single chromatographic or electrophoretic procedure is capable of resolving the complex mixture of peptides that results from a global proteolytic digest of a proteome. Therefore, combining two or more orthogonal (multimodal) separation procedures dramatically improves the overall resolution and results in a larger number of peptides being identified from complex proteome digests. Separation of a proteome digest is a particularly challenging analytical problem due to the large number of peptides and the wide concentration dynamic range. While it has been demonstrated that increasing the number of dimensions of separation prior to MS analysis increases the number of peptides that may be identified, a balance between the time invested and the overall results obtained must be carefully considered. This manuscript provides a review of two- and three-dimensional peptide separation strategies combined with MS for the analysis of complex peptide mixtures.

Chromatography, Liquid↗
PubMed2005

Capture of a monoclonal antibody and prediction of separation conditions using a synthetic multimodal ligand attached on chips and beads.

A synthetic ligand called 2-mercapto-5-benzimidazolesulfonic acid has been successfully used for the specific chromatographic capture of antibodies from a cell culture supernatant. Adsorption occurred at physiological ionic strength and pH range between 5.0 and 6.0, with some binding capacity variations within this pH range: antibody uptake increased when the pH decreased. With very dilute feedstocks, as was the case with the cell culture supernatant under investigation, it was found that the pH had to be slightly lowered to get a good antibody sorption capacity. To optimize separation conditions, a preliminary study was made using ProteinChip Arrays that displayed the same chemical functionalities as the resin. Arrays were analyzed using SELDI-MS. By this mean, it was possible to cross-over simultaneously different pH conditions at the adsorption and the desorption steps. Best conditions were implemented for preparative separation using regular lab-scale columns. At pH 5.2, antibody adsorption was not complete, while at pH 5.0 the antibody was entirely captured. pH 9 was selected at elution, rather than pH 8.0 or 10.0, and resulted in a complete desorption of antibodies from the column. Benefits of the prediction of separation conditions of antibodies on MBI beads using SELDI-MS were a significant reduction in analysis time and in sample volume. This was possible because the separation of IgG on the chip surface did mimic very well the separation on beads.

Adsorption↗
PubMed2006

Chiral separation and quantification of R/S-amphetamine, R/S-methamphetamine, R/S-MDA, R/S-MDMA, and R/S-MDEA in whole blood by GC-EI-MS.

The enantioselective composition of the amphetamines is of interest, as the enantiomers show differences in their pharmacological effects and several methods for chiral separation of amphetamines have been described. Only a few methods have used whole blood as matrix and none of these separates both classic amphetamines (amphetamine and methamphetamine) and designer amphetamines (MDA, MDMA and MDEA). The aim of this study was, therefore, to develop a method for enantioselective analysis of AM, MA, MDA, MDMA, and MDEA in whole blood. The amphetamines were extracted from 0.5 g of whole blood by liquid-liquid extraction. After derivatization with R-MTPCl, the resulting diastereomers were separated by GC on a HP-5MS column and detected by SIM-MS. R-MTPCl was used as derivatization reagent because of the stability of this reagent and good separation of these analytes. Through the method, development time and temperature of the derivatization were optimized, and by admixture of 0.02% triethylamine it became possible to detect the amphetamines in adequately low concentrations as more analytes were derivatized. The method was validated and it was linear from 0.004 to 3 microg/g per enantiomer. The accuracy was within 91-115%, while the repeatability and reproducibility were < or =15% R.S.D. A method suitable for enantioselective separation and analysis of the amphetamines has been achieved, and the method was applied to analysis of whole blood samples originating from traffic and criminal cases and post mortem cases.

3,4-Methylenedioxyamphetamine↗
PubMed2006

Utilisation of controlled pore topology for the separation of bioparticles in a mixed-glass beads column.

To study the flow of shaped particles in porous media, elution of spherical and rod-like micro-organisms was performed through beds of spherical glass beads. A 0.04 cm/s constant flow rate was used with 5 microm yeast suspensions, 1 microm latex micro-spheres and rod-like bacilli Lactobacillus bulgaricus 6 microm long and 0.5 microm in diameter. Yeast cells' diameter is close to the bacilli length and micro-spheres have the same diameter as bacilli. All particle types have similar density. To make the different packing beds, 1.125 mm coarse beads and 0.1115 mm fine beads were used. Experiments were carried out using a column loaded with the binary packing (volume fraction of coarse particles in the mixture 0.7) or a monosize packing with the same amount of coarse or fine particles as used in the binary packing. Analysis of experimental results was based on two models: pure exclusion effect and hydrodynamic separation model [hydrodynamic chromatography (HDC)]. Results for spheres show that the classic HDC model fits to the experimental data whenever the ratio of particle size to the pathway bend scale is high ( approximately 1/100, micro-spheres). However, if this ratio increases and becomes approximately 1/20, the HDC model needs to be corrected due to the effect of channel wall curvature on exclusion. This led to a modified HDC equation of the form R=B/(1+2lambda-2.8lambda(2)), where R is the retention, lambda is the aspect ratio and constant B>or=1. Bacillus separation follows an exclusion mechanism, since pore topology is important in the separation of shaped particles when the aspect ratio approaches lambda=0.1. In the case of a binary packing bed, rod-like particles display a different behaviour than the one exhibited by the spherical particles of the same scale as bacilli, either in length or in diameter. This may be explained by the interaction between rod-like bacilli and the bed's pore topology. A generalised exclusion model for particles was proposed to be R=A/(1-lambda)(z), where A is the coefficient proportional to the tortuosity and the parameter z=1, 2 or 3 depends mainly on pore shape. Controlled pore topology opens interesting applications for bio-separation (in porous micro-fluidic devices, deep bed filtration) and might be especially important for macromolecules and micro-organisms separation with different shapes.

Bacillus↗
PubMed2006

PVC removal from mixed plastics by triboelectrostatic separation.

Ever increasing oil price and the constant growth in generation of waste plastics stimulate a research on material separation for recycling of waste plastics. At present, most waste plastics cause serious environmental problems due to the disposal by reclamation and incineration. Particularly, polyvinyl chloride (PVC) materials among waste plastics generates hazardous HCl gas, dioxins containing Cl, and so on, which lead to air pollution and shorten the life of incinerator, and it makes difficultly recycling of other plastics. Therefore, we designed a bench scale triboelectrostatic separator for PVC removal from mixed plastics (polyvinyl chloride/polyethylene terephthalate), and then carried out material separation tests. In triboelectrostatic separation, PVC and PET particles are charged negatively and positively, respectively, due to the difference of the work function of plastics in tribo charger of the fluidized-bed, and are separated by means of splitter through an opposite electric field. In this study, the charge efficiency of PVC and PET was strongly dependent on the tribo charger material (polypropylene), relative humidity (below 30%), air velocity (over 10 m/s), and mixture ratio (PET:PVC=1:1). At the optimum conditions (electrode potential of 20 kV and splitter position of -2 cm), PVC rejection and PET recovery in PET products were 99.60 and 98.10%, respectively, and the reproducibility of optimal test was very good (+/-1%). In addition, as a change of splitter position, we developed the technique to recover high purity PET (over 99.99%) although PET recovery decreases by degrees.

Air Movements↗
PubMed2004

Solubility and phase separation of benzocaine and salicylic acid in 1,4-dioxane-water mixtures at several temperatures.

The solubilities of benzocaine and salicylic acid were determined in water-dioxane mixtures at several temperatures (5-40 degrees C for benzocaine and 10-40 degrees C for salicylic acid). The solubility curves as a function of dioxane ratio showed a maximum at 90% dioxane at all temperatures. Above 25 degrees C, the homogeneous mixture splits into two liquid immiscible phases. For benzocaine, the initial dioxane concentration range at which phase separation takes place increased with temperature (50-60% at 25 degrees C, 50-70% at 30-35 degrees C and 40-70% at 40 degrees C). For salicylic acid, the dioxane concentration required for phase separation (40-60% dioxane) did not change with temperature. Phase separation was not related to solid phase changes (polymorphism or solvates). The phase composition and drug extraction at the drug-rich phase were determined. The apparent enthalpies of the solution process were a nonlinear function of the dioxane ratio for both drugs. The apparent enthalpy of solution of benzocaine was larger than that expected at the upper limit of phase separation (70% dioxane), whereas for salicylic acid the apparent enthalpy of solution decreased abruptly at the region corresponding to phase separation (40-70% dioxane). Both drugs showed a nonlinear pattern of enthalpy-entropy compensation.

Benzocaine↗
PubMed2005

Separation of nicotinic acid and its structural isomers using 1-ethyl-3-methylimidazolium ionic liquid as a buffer additive by capillary electrophoresis.

The growing interest in application of ionic liquids (ILs) in analytical chemistry has been observed. The aim of presented investigation was to verify whether ILs would be a suitable modifier of the background electrolyte (BGE) for pharmaceutical analysis of the closely related drug analogues. The study demonstrates the use of 1-ethyl-3-methylimidazolium tetrafluoroborate (1E-3MI-TFB) ionic liquid as modifiers in the separation of nicotinic acid and its structural isomers by capillary electrophoresis. Dependences of the ionic liquid concentration in a BGE on the separation parameters like migration time, resolution factor and width at peak's baseline have been compared. The separation mechanism involves the free imidazolium ions, which can interact with inner surface of the capillary wall. Increased 1E-3MI-TFB concentration to 150 mmol/L caused decrease of migration times of analytes, improve peaks shape and increase of separation performances. At this ionic liquid concentration in a BGE resolution factor between nicotinic and isonicotinic acids increased to 1.86. The proposed CE separation procedure is highly reproducible and can be applied in qualitative and quantitative analysis of carboxylic acids.

Buffers↗
PubMed2006

Separation of fibrate-type antihyperlipidemic drugs by capillary electrophoresis and their quantitation in pharmaceuticals.

Six antihyperlipidemic agents-bezafibrate, ciprofibrate, clofibrate, clofibric acid, fenofibrate and gemfibrozil were separated by means of capillary electrophoresis, using unmodified fused silica tubing of 75 microm internal diameter and 87 cm length (65 cm to the UV detector at 227 nm). Migration time and selectivity were examined in differing pH of separation buffer, varying separation voltage and differing temperature. Optimal separation was achieved using 1/15 M phosphate buffer pH 10, 240 V/cm at 25 degrees C. The optimal separation conditions were then used to elaborate the method of quantitation of bezafibrate, ciprofibrate and gemfibrozil in Bezamidin, Lipanor and Gemfibral pharmaceuticals. The clofibric acid was used as internal standard. The calibration curve was constructed from 0.2 to 0.8 mg/ml of each compound and 0.5 mg/ml of internal standard. The calibration data were proved to be linear by Mandel and Lack-of-fit tests. Statistical evaluation of results proved proper recovery of elaborated method (102.42, 97.32 and 101.51%, respectively) and good repeatability (9.51, 5.52 and 11.15%, respectively). The linearity of recovery was also tested by analyzing increasing amount of the samples. Three fortified samples of each drug were also analyzed to perform additional accuracy validation.

Bezafibrate↗
PubMed2006

Rapid separation and determination of structurally related anthraquinones in Rhubarb by pressurized capillary electrochromatography.

A pressurized capillary electrochromatography (pCEC) with monolithic column has been developed for the rapid separation and determination of five structurally related anthraquinones in Rhubarb. The possibility of rapid separation resulted from the unique pore structure with high permeability and favorable mass transfer characteristics of the monolithic stationary phase. The effect factors such as organic modifier, acidity and concentration of running buffer, separation voltage were investigated to acquire the optimum condition. In the 220 nm wavelengths, the five anthraquinones could be baseline-separated rapidly within 5 min with the separation voltage of -20 kV in 10 mmol/L phosphate buffer (pH 6.2) containing 65% acetonitrile. The calibration graphs of rhein, aloe-emodin, emodin chrysophanol and physcion were linear by plotting the peak area against the analytes concentration over the range of 0.2-65, 0.1-30, 0.1-55, 0.5-30 and 0.5-55 microg/mL, respectively. The detection limits of five anthraquinones were ranged from 0.06 to 0.2 microg/mL and the recoveries of Rhubarb samples were about 81.3-86.4% (R.S.D.< or = 5.2%). This proposed method was successfully applied to determination of the five analytes in Rhubarb with satisfactory results.

Anthraquinones↗