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Electrokinetic Chromatography (electrokinetic + chromatography)
Kinds of Electrokinetic Chromatography Selected AbstractsSeparation and Detection of Narcotic Drugs on a Microchip Using Micellar Electrokinetic Chromatography and ElectrochemiluminescenceELECTROANALYSIS, Issue 6 2008Yan Du Abstract A new approach for fast and sensitive electrochemiluminescence (ECL) detection of narcotic drugs on a microchip after separation by micellar electrokinetic chromatography (MEKC) is presented, taking the cocaine and its hydrolysate ecgonine as the test analytes. The mixture of hydrophilic BMIMBF4 ionic liquid (IL) and sodium dodecyl sulfate (SDS) was used directly as the buffer of MEKC with less noisy baselines, lower electrophoretic current and satisfactory separation performance. This developed microchip MEKC,ECL system was successfully applied to the determination of two very similar narcotics, heroin and codeine, within 100s in urine sample and was demonstrated as a promising method in clinical and forensic analysis. [source] Cover Picture: Electrophoresis 13'2010ELECTROPHORESIS, Issue 13 2010Article first published online: 30 JUN 2010 Issue no. 13 is a special issue on "Food and Beverage Analysis" comprising 23 contributions distributed over four distinct parts. Part I "presents six review papers, five of them are focused on the use of capillary electromigration techniques for detecting enantiomers, nucleosides, nucleotides, pesticides and contaminants in foods as well as foodborne pathogens". The sixth review deals with the application of two-dimensional electrophoresis to investigate food allergens. A series of original contributions on the use of CE, CEC and MEKC in the analysis of food constituents are grouped in Part II. Part III presents "Works on the detection of genetically modified foods by CGE and the analysis of antibiotics and antioxidants by microemulsion electrokinetic chromatography". Finally, Part IV is on the use of CE-MS to analyze endocrine disruptors and polyphenols in different food matrices, and on the speciation analysis of arsenic and selenium compounds in different foodstuffs by capillary electrophoresis-inductively coupled plasma-mass spectrometry. [source] Simultaneous determination of memantine and amantadine in human plasma as fluorescein derivatives by micellar electrokinetic chromatography with laser-induced fluorescence detection and its clinical applicationELECTROPHORESIS, Issue 11 2010Hsin-Hua Yeh Abstract A nonionic surfactant MEKC method with LIF detection was developed for the simultaneous determination of memantine, an anti-Alzheimer's disease agent, and amantadine, an anti-Parkinson's disease drug, in human plasma. Before analysis, the plasma samples were pretreated by liquid,liquid extraction with ethyl acetate, and derivatized with 6-carboxyfluorescein N -hydroxysuccinimide ester. The chemical derivatization is performed with 6-carboxyfluorescein N -hydroxysuccinimide ester in ACN , 5,mM pH 9.0 borate buffer (40:60, v/v) at 35°C for 3,h. After the derivatization reaction, hydrodynamic injection (0.5,psi, 8,s) was used to introduce the derivatized solution, and the separation was performed in borate buffer (30,mM, pH 9.5) with the nonionic surfactant Brij-35® (0.07%, w/v); the separation voltage was 6,kV. The linear ranges of the method for the determination of memantine and amantadine in human plasma were over a range of 2.0,60.0,ng/mL. The detection limit was 0.5,ng/mL (S/N=3). This method was applied successfully to monitor the concentration of memantine or amantadine in patients with Alzheimer's disease or Parkinson's disease. [source] Liposomes for entrapping local anesthetics: A liposome electrokinetic chromatographic studyELECTROPHORESIS, Issue 9 2010Jana Lokajová Abstract Bupivacaine is a lipophilic, long-acting, amide class local anesthetic commonly used in clinical practice to provide local anesthesia during surgical procedures. Several cases of accidental overdose with cardiac arrest and death have been reported since bupivacaine was introduced to human use. Recent case reports have suggested that Intralipid (Fresenius Kabi) is an effective therapy for cardiac toxicity from high systemic concentrations of, e.g. bupivacaine, even though the mechanism behind the interaction is not fully clear yet. Our long-term aim is to develop a sensitive, efficient, and non-harmful lipid-based formulation to specifically trap harmful substances in vivo. In this study, the in vitro interaction of local anesthetics (bupivacaine, prilocaine, and lidocaine) with Intralipid or lipid vesicles containing phosphatidylglycerol, phosphatidylcholine, cardiolipin, cholesterol, and N -palmitoyl- D - erythro -sphingosine (ceramide) was determined by liposome electrokinetic chromatography. The interactions were evaluated by calculating the retention factors and distribution constants. Atomic force microscopy measurements were carried out to confirm that the interaction mechanism was solely due to interactions between the analytes and the moving pseudostationary phase and not by interactions with a stationary lipid phase adsorbed to the fused-silica wall. The heterogeneity of the liposomes was also studied by atomic force microscopy. The liposome electrokinetic chromatography results demonstrate that there is higher interaction between the drugs and negatively charged liposome dispersion than with the commercial Intralipid dispersion. [source] Cyclodextrin-based nonaqueous electrokinetic chromatography with UV and mass spectrometric detection: Application to the impurity profiling of amiodarone,ELECTROPHORESIS, Issue 17 2008Roelof Mol Abstract The potential of nonaqueous electrokinetic chromatography (NAEKC) using cyclodextrins (CD) for the analysis of basic drugs and related compounds was evaluated. Both UV absorbance and mass spectrometric (MS) detection were employed. Addition of neutral CD to the NA background electrolyte did not significantly enhance the separation of a test mixture of basic drugs, and no change in selectivity was observed. In contrast, anionic single-isomer-sulfated CD strongly added to the selectivity of the NAEKC system inducing an improved resolution among the test compounds and increasing the migration time window. The applicability of the NAEKC system using anionic CD is demonstrated by the profiling of a sample of the drug amiodarone that had been stored for 1,year at room temperature. Amiodarone is poorly soluble in water. NAEKC-UV analysis indicated the presence of at least seven impurities in the amiodarone sample. In order to identify these compounds, the NAEKC system was coupled directly to electrospray ionization (ESI) ion-trap MS. The total of detected impurities increased to 12 due to the added sensitivity and selectivity of MS detection. Based on the acquired MS/MS data, three sample constituents could be identified as ,known' impurities (British Pharmacopoeia), whereas for three unknown impurities molecular structures could be proposed. Estimated limits of detection for amiodarone using the NAEKC method were 1,,g/mL with UV detection and 15,ng/mL with ESI-MS detection (full-scan). Based on relative responses, the impurity content of the stored drug substance was estimated to be 0.33 and 0.47% using NAEKC-UV and NAEKC-ESI-MS, respectively. [source] Length-dependent DNA separations using multiple end-attached peptide nucleic acid amphiphiles in micellar electrokinetic chromatographyELECTROPHORESIS, Issue 13 2008Jeffrey M. Savard Abstract End-labeled free-solution electrophoresis (ELFSE) is an alternative approach to gel-based methods for size-based electrophoretic separation of DNA. In ELFSE, an electrically neutral "drag-tag" is appended to DNA to add significant hydrodynamic drag, thereby breaking its constant charge-to-friction ratio. Current drag-tag architecture relies on covalent attachment of polymers to each DNA molecule. We have recently proposed the use of micellar drag-tags in conjunction with sequence-specific hybridization of peptide nucleic acid amphiphiles (PNAAs). This work investigates the effect of multiple PNAA attachment on DNA resolution using MEKC. Simultaneous PNAA hybridization allows for the separation of long DNA targets, up to 1012,bases, using micellar drag-tags. Each PNAA handle independently interacts with the micellar phase, reducing the overall mobility of this complex relative to individual PNAA binding. The sequence- and size-based dependence of this separation technique is maintained with multiple PNAA binding over a range of DNA sizes. Results are accurately described by ELFSE theory, yielding , = 54 for single-micelle tagging and , = 142 for dual-micelle tagging. This method is the first example of a non-covalent drag-tag used to separate DNA of 1000,bases based on both size and sequence. [source] Compositional effects on electrophoretic and chromatographic figures of merit in electrokinetic chromatography with cetyltrimethylammonium bromide/sodium octyl sulfate vesicles as the pseudostationary phase.ELECTROPHORESIS, Issue 5 2008Part 1: Effect of the phase ratio Abstract The effect of the phase ratio on the electrophoretic and chromatographic properties of unilamellar vesicles comprised of cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS) was investigated in EKC. The surfactant concentration of the vesicles was 0.9, 1.2, 1.5, and 1.8% w/v, with a mole ratio of 1:3.66 (CTAB/SOS). Results were compared to those obtained using SDS micelles at concentrations of 1.0% (w/v, 35,mM) and 1.5% (52,mM). The CTAB/SOS vesicles (0.9,1.8% w/v) provided a significantly larger elution range (5.7,,,tves/t0,,,8.7) and greater hydrophobic (methylene) selectivity (2.8,,,,CH2,,,3.1) than SDS micelles (3.1,,,tmc/t0,,,3.3; ,CH2,=,2.2). Whereas the larger elution range can be attributed to the 25% reduction in EOF due to the interaction of unaggregated CTAB cations and the negatively charged capillary wall, the higher methylene selectivity is likely due to the lower concentration of water expected in the CTAB/SOS vesicle bilayer compared to the Palisades layer of SDS micelles. For a given phase ratio, CTAB/SOS vesicles are somewhat less retentive than SDS micelles, although retention factors comparable to those observed in 1.0,1.5% SDS can be obtained with 1.5,1.8% CTAB/SOS. A linear relationship was observed between phase ratio and retention factor, confirming the validity of the phase ratio model for these vesicles. Unique polar group selectivities and positional isomer shape selectivities were obtained with CTAB/SOS vesicles, with both types of selectivities being nearly independent of the phase ratio. For four sets of positional isomers, the elution order was always para < ortho < meta. Finally, the thermodynamics of solute retention was qualitatively similar to that reported for other surfactant aggregates (micelles and microemulsions); the enthalpic contribution to retention was consistently favorable for all compounds, whereas the entropic contribution was favorable only to hydrophobic solutes. [source] Determination of amino acids by micellar EKC: Recent advances in method development and novel applications to different matricesELECTROPHORESIS, Issue 1 2008Paolo Iadarola Professor Abstract The extensive use of CE for the analysis of amino acids has been well documented in a series of research articles and reviews. Aim of this report is to address the attention of the reader on the recent advances of micellar electrokinetic chromatography for the separation and determination of these analytes. Enhancements in selectivity of this technique through the use of pseudostationary phases containing mixed micelles, polymers, and chiral selectors are presented. Selected applications concerning separation and quantitation of even minute amounts of amino acids in: (i) biological fluids; (ii) microdialysates; (iii) plant cells; (iv) food stuff; and (v) pharmaceutical formulations have also been covered. Advantages of MEKC over other techniques for the amino acid analysis have been underlined. [source] Rapid determination of acyclovir in plasma and cerebrospinal fluid by micellar electrokinetic chromatography with direct sample injection and its clinical applicationELECTROPHORESIS, Issue 4 2006Hsin-Hua Yeh Abstract A simple MEKC with UV detection at 254,nm for analysis of acyclovir in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of acyclovir from biological matrix was performed at 25°C using a BGE consisting of Tris buffer with SDS as the electrolyte solution. Several parameters affecting the separation of the drug from biological matrix were studied, including the pH and concentrations of the Tris buffer and SDS. Using dyphylline as an internal standard, the linear ranges of the method for the determination of acyclovir in plasma and in CSF all exceeded the range of 2,50,,g/mL; the detection limit of the drug in plasma and in CSF (S/N = 3; injection 3.45,kPa, 5,s) was 1.0,,g/mL. The applicability of the proposed method for determination of acyclovir in plasma and CSF collected at 8,h after intravenous administration of 500,mg acyclovir (Zovirax®) in two patients with herpes simplex encephalitis was demonstrated. [source] Capillary electrophoresis-laser induced fluorescence analysis of endogenous damage in mitochondrial and genomic DNAELECTROPHORESIS, Issue 13 2005Michaela Wirtz Abstract Reactive oxygen molecules are formed in vivo as by-products of normal aerobic metabolism. All organisms dependent on oxygen are inevitably exposed to these species so that DNA damage can occur in both genomic and mitochondrial DNA (mtDNA). In order to determine endogenous DNA damage we have developed an analytical method that involves the isolation and hydrolysis of genomic DNA or mtDNA, the labeling of modified and unmodified nucleotides and micellar electrokinetic chromatography with laser-induced fluorescence detection. With this method we have found etheno-adenine, thymine glycol, uracil, hypoxanthine, and 5-methylcytosine. These were identified by the addition of internal standards to the genomic or mtDNA. There are a large number of other signals in the electropherograms of mtDNA that we have never found in genomic DNA analysis because they are at lower concentration in the genome. In the DNA of untreated patients with chronic lymphocytic leukemia (CLL), uracil and high levels of etheno-adenine were found, which can be explained by antioxidant enzyme alterations and oxidative stress in the CLL lymphocytes. [source] Conformational effects on the performance and selectivity of a polymeric pseudostationary phase in electrokinetic chromatographyELECTROPHORESIS, Issue 4-5 2005Jonathan P. McCarney Abstract The effect of the conformation of a polymeric pseudostationary phase on performance and selectivity in electrokinetic chromatography was studied using an amphiphilic pH-responsive polymer that forms compact intramolecular aggregates (unimer micelles) at low pH and a more open conformation at high pH. The change in conformation was found to affect the electrophoretic mobility, retention, selectivity, and separation efficiency. The low-pH conformer has higher electrophoretic mobility and greater affinity for most solutes. The unimer micelle conformation was also found to provide a solvation environment more like that of micelles and other amphiphilic self-associative polymers studied previously. It was not possible to fully characterize the effect of conformation on efficiency, but very hydrophobic solutes with long alkyl chains appeared to migrate with better efficiency when the unimer micelle conformation was employed. The results imply that polymers with a carefully optimized lipophilic-hydrophilic balance that allow self-association will perform better as pseudostationary phases. In addition, the results show that electrokinetic chromatography is a useful method for determining the changes in solvation environment provided by stimuli-responsive polymers with changes in the conditions. [source] Monomeric and polymeric anionic gemini surfactants and mixed surfactant systems in micellar electrokinetic chromatography.ELECTROPHORESIS, Issue 2 2005Part II: Characterization of chemical selectivity using two linear solvation energy relationship models Abstract Sodium di(undecenyl) tartarate monomer (SDUT), a vesicle-forming amphiphilic compound possessing two hydrophilic carboxylate headgroups and two hydrophobic undecenyl chains, was prepared and polymerized to form a polymeric vesicle (i.e., poly-SDUT). The anionic surfactants of SDUT and poly-SDUT (carboxylate head group) and sodium dodecyl sulfate, SDS (sulfate head groups) as well as mixed surfactant systems (SDS/SDUT, SDS/poly-SDUT, and SDUT/poly-SDUT) were applied as pseudostationary phases in micellar electrokinetic chromatography (MEKC). Two linear solvation energy relationship (LSER) models, i.e., solvatochromic and solvation parameter models, were successfully applied to investigate the effect of the type and composition of pseudostationary phases on the retention mechanism and selectivity in MEKC. The solvatochromic and solvation parameter models were used to help understand the fundamental nature of the solute-pseudostationary phase interactions and to characterize the properties of the pseudostationary phases (e.g., solute size and hydrogen bond-accepting ability for all pseudostationary phases). The solute types were found to have a significant effect on the LSER system coefficients and on the predicted retention factors. Although both LSER models provide the same information, the solvation parameter model is found to provide much better results both statistically and chemically than the solvatochromic model. [source] Recent progress in the use of soluble ionic polymers as pseudostationary phases for electrokinetic chromatographyELECTROPHORESIS, Issue 23-24 2004Christopher P. Palmer Abstract This review concerns the development, characterization, and application of soluble ionic polymeric materials as pseudostationary phases for electrokinetic chromatography since 2002. Cationic polymers, anionic siloxanes, polymerized surfactants (micelle polymers), and chiral polymers are considered. The use of stable suspensions of polymer nanoparticles in electrokinetic chromatography is also reviewed. [source] Determination of the chiral and achiral related substances of methotrexate by cyclodextrin-modified micellar electrokinetic chromatographyELECTROPHORESIS, Issue 16 2004Roberto Gotti Abstract A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method for the determination of the most important potential impurities of methotrexate (MTX): 2,4-diamino-6-(hydroxymethyl)pteridine, aminopterine hydrate, 4-[N -(2-amino-4-hydroxy-6-pteridinylmethyl)- N -methylamino] benzoic acid, 4-[N -(2,4-diamino-6-pteridinylmethyl)- N -methylamino] benzoic acid, and the distomer D -MTX is presented. The MEKC separation of these compounds was optimized by applying a step-by-step approach. The addition of ,-CD to a conventional MEKC system, based on sodium dodecyl sulfate (SDS) as surfactant, showed to be essential for the enantioresolution of racemic MTX as well as for the separation of the achiral impurities. To achieve high-resolution factor between the peaks adjacent to the main component (L -MTX), as required in the analysis of related impurities, the separation conditions were stressed; in particular, the addition of methanol to the CD-MEKC system resulted in a very effective choice. Under the optimized final conditions (100 mM SDS and 45 mM ,-CD in a mixture of 50 mM borate buffer, pH 9.30-methanol (75:25 v/v)), the method was validated showing a general adequate accuracy (93,106% recovery) in the determination of L -MTX related substances at the impurity level of 0.12% w/w with a relative standard deviation (RSD)% lower than 8% (n = 4). The method was successfully applied to the analysis of pharmaceuticals (tablets and injections) which showed to contain the distomer D -MTX as major impurity and aminopterine hydrate as a further related substance in the commercial tablets. [source] Orthogonal separations of nicotine and nicotine-related alkaloids by various capillary electrophoretic modesELECTROPHORESIS, Issue 9 2004Alex Marsh Abstract The migration behaviour of nicotine and related tobacco alkaloids was investigated using three different capillary electrophoretic (CE) modes. Novel separations were achieved both using microemulsion electrokinetic chromatography (MEEKC) and nonaqueous CE (NACE). Improved resolution compared to previous studies was obtained using free-solution CE (FSCE). Each technique resulted in different, orthogonal separation selectivity. The suitability of each method for application to the analysis of nicotine lozenges is discussed. The FSCE method was applied to the analysis of nicotine lozenges due to its compatibility with an established lozenge extraction solvent. The method used gave good injection precision and linearity. Good agreement of CE and high-performance liquid chromatography (HPLC) results was obtained. The CE method is therefore considered suitable for the quantitative determination of nicotine in nicotine lozenges. [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] Capillary electrophoresis of amphipathic ,-helical peptide diastereomersELECTROPHORESIS, Issue 1 2004Traian V. Popa Abstract We have made a rigorous assessment of the ability of capillary electrophoresis to resolve peptide diastereomers through its application to the separation of a series of synthetic 18-residue, amphipathic ,-helical monomeric peptide analogues, where a single site in the centre of the hydrophobic face of the ,-helix is substituted by 19 L - or D -amino acids. Such L - and D -peptide pairs have the same mass-to-charge ratio, amino acid sequence and intrinsic hydrophobicity, varying only in the stereochemistry of one residue. CE approaches assessed in their ability to separate diastereomeric peptide pairs included capillary zone electrophoresis (uncoated capillary), micellar electrokinetic chromatography (uncoated capillary in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, CHAPS), open-tubular capillary electrochromatography (C8 -coated capillary in the presence of 25% 2,2,2-trifluoroethanol (TFE) or 25% ethanol). Overall, the OT-CEC methods were the most effective at separating the most peptide pairs, particularly for those containing hydrophilic side chains. However, the MEKC approach proved most effective for separation of peptide pairs containing hydrophobic or aromatic side chains. [source] Recent advances in capillary electrophoresis and capillary electrochromatography of peptidesELECTROPHORESIS, Issue 22-23 2003Václav Ka Abstract An overview of the recent developments in the applications of high-performance capillary electromigration methods, namely zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography, to analysis, preparation, and physicochemical characterization of peptides is presented. New approaches to the theoretical description and experimental verification of the electromigration behavior of peptides and the methodological aspects of capillary electroseparations of peptides, such as rational selection of separation conditions, sample treatment, and suppression of adsorption, are discussed, and new developments in individual separation modes and new designs of detection systems applied to peptide separations are shown. Several types of applications of capillary electromigration methods to peptide analysis are presented: quality control and purity tests, determination in biomatrices, monitoring of physical and chemical changes and enzymatic conversions, amino acid and sequence analysis, and peptide mapping. The examples of micropreparative peptide separations are given and capabilities of capillary electromigration techniques to provide important physicochemical characteristics of peptides are demonstrated. [source] In vivo simultaneous monitoring of ,-aminobutyric acid, glutamate, and L -aspartate using brain microdialysis and capillary electrophoresis with laser-induced fluorescence detection: Analytical developments and in vitro/in vivo validationsELECTROPHORESIS, Issue 18 2003Valérie Sauvinet Abstract ,-Aminobutyric acid (GABA), glutamate (Glu), and L -aspartate (L -Asp) are three major amino acid neurotransmitters in the central nervous system. In this work, a method for the separation of these three neurotransmitters in brain microdialysis samples using a commercially available capillary electrophoresis (CE) system has been developed. Molecules were tagged on their primary amine function with the fluorogene agent naphthalene-2,3-dicarboxaldehyde (NDA), and, after separation by micellar electrokinetic chromatography, were detected by laser-induced fluorescence using a 442 nm helium-cadmium laser. The separation conditions for the analysis of derivatized neurotransmitters in standard solutions and microdialysates have been optimized, and this method has been validated on both pharmacological and analytical basis. The separation of GABA, Glu, and L -Asp takes less than 10 min by using a 75 mmol/L borate buffer, pH 9.2, containing 70 mmol/L SDS and 10 mmol/L hydroxypropyl-,-cyclodextrin and +,25 kV voltage. The detection limits were 3, 15 nmol/L and, 5 nmol/L for GABA, Glu, and L -Asp, respectively. Moreover, submicroliter samples can be analyzed. This method allows a simple, rapid and accurate measurement of the three amino acid neurotransmitters for the in vivo brain monitoring using microdialysis sampling. [source] Separation of Escherichia coli 055:B5 lipopolysaccharide and detoxified lipopolysaccharide by high-performance capillary electrophoresisELECTROPHORESIS, Issue 17 2003Nicola Volpi Abstract A rapid, highly sensitive and reproducible high-performance capillary electrophoresis (HPCE) method (electrokinetic chromatography with sodium dodecyl sulfate) is described for the determination of the lipopolysaccharide (LPS) and detoxified LPS (D-LPS), produced by both alkaline treatment in anhydrous conditions and mild acid hydrolysis, from Escherichia coli 055:B5 bacteria. LPS and D-LPS are separated and readily determined within 25 min on an uncoated fused-silica capillary using normal polarity at 20 kV and detection at 200 nm. A linear relationship (correlation coefficient greater than about 0.97) was found for the LPS and the two D-LPS species over a wide range of concentrations, from approximately 120 to 360 ng, with a detection sensitivity less than about 100 ng. Furthermore, HPCE was able to separate several molecular species mainly due to the presence of populations with O -specific polysaccharides of distinct and increasing mean chain lengths. This approach could be of great importance for the quantitative determination of LPS and D-LPS during the purification and preparation processes, also considering the importance of D-LPS in the preparation of human vaccines, and for the qualitative evaluation of the heterogeneity of LPS and the O -polysaccharide components. [source] Enantioselectivity of alcohol-modified polymeric surfactants in micellar electrokinetic chromatographyELECTROPHORESIS, Issue 15 2003Jepkoech Tarus Abstract A novel method of modifying sodium undecanoyl- L -leucinate (SUL) micelles employed in chiral separation of analytes in micellar electrokinetic chromatography (MEKC) to enhance selectivity toward specific analytes is discussed. The current study aimed at modifying the SUL micelles by introducing different alcohols into the mono-SUL micelles. The micellar solutions were then polymerized in the presence of alcohols followed by postpolymerization extraction of the alcohols to yield alcohol-free polymeric surfactants (poly- L -SUL). The effects of hexanol (C6OH) and undecylenyl alcohol (C11OH) on micellar properties of this surfactant were investigated by use of surface tensiometry, fluorescence spectroscopy, pulsed field gradient-nuclear magnetic resonance (PFG-NMR), and MEKC. The surface tension and PFG-NMR studies indicated an increase in the critical micelle concentration (cmc) and micellar size upon increasing the alcohol concentration. Fluorescence measurements suggested that alcohols induce closely packed micellar structures. Coumarinic and benzoin derivatives, as well as (±)-1, 1'-binaphthyl-2,2'-dihydrogen phosphate (BNP) were used as test analytes for MEKC experiments. Examination of MEKC data showed remarkable resolutions and capacity factors of coumarinic derivatives obtained with modified poly- L -SUL as compared to the unmodified poly- L -SUL. Evaluation of fluorescence, PFG-NMR, and MEKC data suggest a strong correlation between the polarity and hydrodynamic radii of alcohol-modified micelles and the resolution of the test analytes. [source] Polymeric alkenoxy amino acid surfactants: I. Highly selective class of molecular micelles for chiral separation of ,-blockersELECTROPHORESIS, Issue 15 2003Syed A. A. Rizvi Abstract Two amino acid-based alkenoxy micelle polymers were synthesized for this study. These include polysodium N -undecenoxy carbonyl- L -leucinate (poly- L -SUCL) and polysodium N -undecenoxy carbonyl- L -isoleucinate (poly- L -SUCIL). The polymerization time and concentration of the synthesized micelle polymers were optimized by 1H-nuclear magnetic resonance (NMR) and capillary electrophoresis (CE) experiments. Detailed physicochemical properties (1H NMR, critical micelle concentration (CMC), optical rotation, partial specific volume, aggregation number, and polarity) were determined, and these molecular micelles were introduced as a pseudostationary phase in micellar electrokinetic chromatography to study the molecular recognition and to develop a method for simultaneous separation of eight chiral ,-blockers. It is found that poly- L -SUCL gives overall better chiral resolution and wider chiral window than poly- L -SUCIL. After optimizing the type of micelle polymer, injection size and temperature, simultaneous separation and enantioseparation of eight ,-blockers were achieved in less than 35 min. A comparison with the amide-type surfactants of the same polar head group and alkyl chain length showed that carbamate-type surfactants always work better than the corresponding amide-type surfactant. [source] Detection of chlorinated quinones using interdigitated electrodes coupled with capillary electrophoresisELECTROPHORESIS, Issue 6 2003Keith B. Male Abstract An array of eight interdigitated microband gold electrodes (IDEs) has been developed together with electrophoretic separation for analysis of chlorinated hydroquinones (ClHQs) and benzoquinones (ClBQs). The IDE chip positioned very close to the separation capillary outlet served as an amplification/detection system without the requirement for frequent "capillary-electrode" alignment. ClHQs, electrophoretically migrating to the IDE surface, were oxidized at +1.1 V by seven electrodes of the array and then detected by the remaining electrode, poised at ,0.1 V. Conversely, ClBQs were detected at +1.1 V by the detecting electrode after having been reduced at the 7 adjacent electrodes poised at ,0.1 V. There was an amplification effect on both the detecting electrode as well as the adjacent electrodes because of the recycle between ClHQs and ClBQs. The detecting "amplification" current response was dependent on the potentials applied, the position of the detecting electrode on the array, the number of adjacent electrodes being used for recycling and the distance between the oxidative and reductive electrodes. Micellar electrokinetic chromatography (MEKC) separation of the analytes was achieved using 30 mM sodium dodecyl sulfate (SDS) with a detection limit in the range of 2,20 ,M. In addition to a facile "capillary-electrode" alignment, the important aspect described here was the capability of detecting through recycling a reduced compound (in the case of ClHQs) at a negative potential to circumvent fouling and electroactive interferences. An appealing feature was also the concurrent oxidation/reduction detection for each compound to ascertain peak assignment, as interfering compounds are less likely to exhibit the same oxidative/reductive characteristics and electrophoretic mobilities as the target analytes. [source] On-line identification of lysergic acid diethylamide (LSD) in tablets using a combination of a sweeping technique and micellar electrokinetic chromatography/77 K fluorescence spectroscopyELECTROPHORESIS, Issue 6 2003Ching Fang Abstract This work describes a novel method for the accurate determination of lysergic acid diethylamide (LSD) in tablets. A technique involving sweeping-micellar electrokinetic chromatography (MEKC) was used for the initial on-line concentration and separation, after which a cryogenic molecular fluorescence experiment was performed at 77 K. Using this approach, not only the separation of LSD from the tablet extract was achieved, but on-line spectra were readily distinguishable and could be unambiguously assigned. The results are in agreement with analyses by gas chromatography-mass spectrometry (GC-MS). Thus, this method, which was found to be accurate, sensitive and rapid, has the potential for use as a reliable complementary method to GC-MS in such analyses. [source] Recent progress in the development, characterization and application of polymeric pseudophases for electrokinetic chromatographyELECTROPHORESIS, Issue 22-23 2002Christopher P. Palmer Abstract This review article details the development, characterization and application of polymeric materials as pseudostationary phases for electrokinetic chromatography over the past two years. Recent developments in cationic polymers and anionic siloxane, acrylamide and polymerized surfactants (micelle polymers) are reviewed. Also reviewed is recent progress in the development and characterization of chiral polymeric phases for chiral separations by electrokinetic chromatography, and application of a polymeric pseudophase with electrospray ionization mass spectrometric detection. [source] Capillary Zone Electrophoresis and Micellar Electrokinetic Capillary Chromatography for Determining Water-Soluble Vitamins in Commercial Capsules and TabletsJOURNAL OF FOOD SCIENCE, Issue 1 2001S-C. Su ABSTRACT: A rapid method was developed for simultaneously determining thiamine, riboflavin, pyridoxine, nicotinamide, nicotinic acid, and ascorbic acid. It was tested on 15 samples. The peaks of all components were cleanly separated with good resolution by capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MECC). CZE was performed with 0.02 M borate buffer, and MECC was performed with 4% acetonitrile in 0.02 M borate/phosphate buffer containing 0.1 M sodium dodecyl sulfate. Average recoveries for all components were 80.3% to 103.7% with coefficients of variation being less than 5%. Thiamine, nicotinic acid, and pyridoxine contents were consistent with those labeled on the packages, but nicotinamide, riboflavin, and ascorbic acid contents of some samples were less. [source] Separation of fatty alcohol ethoxylates by capillary zone electrophoresis and micellar electrokinetic chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 3 2009Ryo Koike Abstract Separation methods based on capillary zone electrophoresis and micellar electrokinetic chromatography were developed to characterize the distribution of ethylene oxide (EO) homologues in the fatty alcohol ethoxylates (FAEs). Prior to the separation, the FAEs were derivatized with 2-fluoro-1-methylpyridinium p -toluenesulfonate (FMPTS) to allow CZE separation and UV detection. To prevent adsorption of cationic analytes onto the inner surface of the capillary and formation of micelles in CZE analysis, a lower pH background solution (BGS) containing a high concentration of acetonitrile was employed. Under optimal conditions, FMPTS-derivatized FAEs with an average EO number of 6 were completely separated within 11 min. For MEKC analysis of the FAEs, dodecyltrimethylammonium chloride (DTAC) was added to the BGS. In the presence of 30 mM DTAC in 10 mM phosphate buffer (pH 2.5) containing 20% (v/v) acetonitrile, superior oligomer separation of the FAEs containing up to 50 EO groups was achieved within 30 min with good analytical reproducibilities. Furthermore, the developed method was applied to the analysis of the FAEs in commercial products such as laundry detergent and fabric softener. [source] Separation and quantification of 9-(alkylthio)acridines by capillary micellar electrokinetic chromatography and capillary liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2007Jana Nejmanová Abstract Various thioacridine derivatives are potential chemotherapeutics against various diseases which are intensively synthesized, characterized, and investigated by many research groups. Efficient, fast, and reliable separation and quantification methods for their analysis are still to be developed. MEKC and capillary LC (CLC) were applied for the separation and quantification of five highly hydrophobic, weakly basic, and structurally similar 9-(alkylthio)acridines. Since the common anionic and cationic surfactants failed to separate the strongly hydrophobic thioacridines by MEKC, sodium cholate was used in an alkaline BGE and successfully employed for their fast separation. In CLC, the weakly basic nature of the thioacridines necessitated use of LiChrosorb RP-select B sorbent as the stationary phase, which combined with a very simple mobile phase methanol/water yielded an efficient chromatographic separation system. Both, the MEKC and CLC optimized separation methods were then applied to quantify the thioacridines within a concentration range of 1.0×10,5,1.0×10,3 mol/L and the obtained experimental results were critically compared. In practical terms, the MEKC analytical method can quantify the analytes much faster but with a lower reliability while the CLC method performs slower analysis with a higher repeatability of the experimental results. [source] Effect of surfactant counterion and organic modifier on the properties of surfactant vesicles in electrokinetic chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2005Stephanie A. Schuster Abstract See original 2005, vol. 28, issue 12, pp. 1399,1408. DOI 10.1002/jssc.200500208 [source] Determination of the purity of ampicillin by micellar electrokinetic chromatography and reversed phase liquid chromatography on a monolithic silica columnJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7-8 2004Milada Dole, alová Abstract A micellar electrokinetic chromatographic (MEKC) method and a fast reversed-phase liquid chromatographic one have been developed for determining the purity of ampicillin. MEKC separation of ampicillin and its related substances was performed with the use of an untreated fused-silica capillary and 40 mM phosphate-borate buffer, pH 7.5 containing 75 mM SDS. The HPLC method employed a monolithic silica C18 column and a mobile phase composed of phosphate buffer, pH 5.2 and ACN, the flow rate being 4.0 mL/min. Both methods were successfully validated. Linearity, relative response factors, limits of quantitation, intermediate precision, and accuracy were evaluated. The methods proved to be fast, reliable, and sufficiently sensitive and, accordingly, well-suited for control of purity of ampicillin substance, injections, and capsules. A combination of both methods can be very useful in the confirmation of impurity profiles. [source] | |||||||||||||