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On-line Preconcentration (on-line + preconcentration)
Selected AbstractsOn-line preconcentration and enantioseparation of thalidomide racemates by CEC with the hyphenation of octyl and norvancomycin monolithsELECTROPHORESIS, Issue 4 2009An-Na Tang Abstract A method was developed for simultaneous preconcentration and chiral separation of thalidomide enantiomers in human urine by CEC in combination with self-concentration and solvent gradient effects. A 4,cm long octyl (C8) monolithic column was hyphenated with a 15,cm long norvancomycin (NVC)-bonded monolithic column via a fluorinated ethylene,propylene interface. Sample solution was injected into the C8 monolithic column, the two thalidomide enantiomers were first preconcentrated on the C8 monolithic column, and then separated with a further concentration on the NVC-bonded monolithic column by CEC. Injection of 34.8,mm plug of sample solution gave 278- and 298-fold enhancement in sensitivity, and detection limits of 90 and 94,,g/L for the two thalidomide enantiomers. Peak areas of the two isomers were linear in a range of 0.5,50,mg/L. The precision for five replicate injections of 10,mg/L were 0.8,0.9 and 1.1,2.3% for the migration time and peak height, respectively. The developed method was applied to the determination of racemic thalidomide in spiked human urine samples. [source] On-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: A dual strategy for integrating sample pretreatment with chemical analysisELECTROPHORESIS, Issue 21 2005Adam S. Ptolemy Abstract Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho -phthalaldehyde/N -acetyl- L -cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector. [source] On-line preconcentration for capillary electrophoresis-atomic fluorescence spectrometric determination of arsenic compoundsELECTROPHORESIS, Issue 12 2004Xue-Bo Yin Abstract An on-line preconcentration method was developed for capillary electrophoresis (CE) with hydride generation-atomic fluorescence spectrometric (HG-AFS) detection of arsenite, arsenate, dimethylarsenic acid, and monomethylarsenic acid. These arsenic species were negatively charged in the sample solution with high pH. When the potential was applied to the electrophoretic capillary, the negatively charged analyte ions moved faster and stacked at the boundary of sample and CE buffer with low pH. So, high sample pH in combination with low buffer pH allowed the injection of large sample volumes (, 1100 nL). Comparison of the preconcentration of analyte solution, prepared with doubly deionized water and that prepared with lake or river water, indicated that preconcentration was independent on the original matrix. With injection of ,1100 nL sample, an enrichment factor of 37,50-fold was achieved for the four species. Detection limits for the four arsenic species ranged from 5.0 to 9.3 ,g·L,1. Precisions (RSDs, n = 5) were in the range of 4.9,6.7% for migration time, 4.7,11% for peak area, and 4.3,7.1% for peak height, respectively. The recoveries of the four species in locally collected water solution spiked with 0.1 ,g·mL,1 (as As) ranged from 83 to 109%. [source] On-line preconcentration and quantitative analysis of peptide hormone of brain and intestine using on-column transient isotachophoresis coupled with capillary electrophoresis/electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008Shifei Xia A new approach was described to achieve very sensitive analysis of peptide hormone of brain and intestine by capillary electrophoresis coupled with a transient isotachophoresis (tITP) preconcentration method. The system used was electrospray ionization mass spectrometry (ESI-MS) as detector and equipped with a sheath flow configuration. The effects of sample matrix, pH and concentration of leading electrolyte (LE), sample injection time, and ESI-MS instrumental parameters on the efficiency of the sample stacking were investigated in detail. Under the optimized conditions, lower than micromole (0.01,µM) concentrations of the peptides were easily detected. Compared to traditional hydrodynamic injection methods, about 40,230-fold increase in detection sensitivity was obtained by this technique. A distinguishing feature of the described approach is that the background electrolyte can serve as terminating electrolyte (TE), which simplifies the process of the experiments. The method was further evaluated by the analysis of low concentration active peptide mixtures spiked in hypothalamus tissue of the rat. Copyright © 2008 John Wiley & Sons, Ltd. [source] Cover Picture: Electrophoresis 16'2010ELECTROPHORESIS, Issue 16 2010Article first published online: 19 AUG 2010 Issue no. 16 is a regular issue with an Emphasis on "Proteins and Proteomics" comprising 20 manuscripts distributed over 4 separate parts. Part I has 7 research articles on various aspects of proteins and proteomics including combinatorial peptide ligand library for accessing low abundance proteins, analysis of membrane proteins, proteomic profiling of human colon cancer cells, quantitative determinations of biomarkers in clinical diagnostics, recombinant factor VIII, analysis of E. coli soluble proteins, and a weakly basic amino-reactive fluorescent label for IEF of proteins and chip electrophoresis. Part II has 2 research articles dealing with the CE analysis of magnetic nanoparticles and a microfluidic magnetic bead impact for cell stimulation. Part III consists of 2 research articles dealing with on-line preconcentration in CE. Instrumentation, devices and various methodologies are described in 9 research articles, which make the content of Part IV. Featured articles include: Combinatorial peptide ligand library plasma treatment: Advantages for accessing low-abundance proteins ((doi: 10.1002/elps.201000188)) Precautions to improve the accuracy of quantitative determinations of biomarkers in clinical diagnostics ((doi: 10.1002/elps.201000243)) Rapid identification of Candida albicans in blood by combined capillary electrophoresis and fluorescence in situ hybridization ((doi: 10.1002/elps.201000138)) [source] Study of electromigration effects on a pH boundary during the on-line electrokinetic preconcentration by capillary electrophoresisELECTROPHORESIS, Issue 16 2010ina Vítková Abstract A contribution to the description of electrokinetic effects on the pH boundary formed by sodium borate pH 9.5 and sodium phosphate pH 2.5 electrolytes for on-line preconcentration of weak acids is presented in this article. Simulations of electrokinetic injections together with experimental studies using contactless conductivity detection verified that the preconcentration is induced mainly by dissociation changes of analytes on the pH boundary and transient ITP state. Moreover, a study of the addition of organic solvent to the injection electrolyte was performed with impressive results. Subnanomolar LODs of hydroxybenzoic acids were achieved with 80% of methanol in the injection electrolyte which represents more than 70,000-fold preconcentration in comparison with classical CZE method. [source] Electrokinetic supercharging-electrospray ionisation-mass spectrometry for separation and on-line preconcentration of hypolipidaemic drugs in water samplesELECTROPHORESIS, Issue 7 2010Mohamed Dawod Abstract Electrokinetic supercharging, a powerful on-line preconcentration technique in CE, was for the first time hyphenated with ESI-MS for the on-line concentration and separation of five hypolipidaemic drugs. The electrophoretic separation was performed in a co-EOF mode using the EOF reversal agent, hexadimethrine bromide, in ammonium bicarbonate electrolyte, pH 9.00. The ionic strength and the amount of methanol in the buffer were optimised in a multivariate manner using artificial neural networks, with the optimal conditions being 60,mM ammonium bicarbonate containing 60% methanol, providing baseline resolution of the five hypolipidaemics within 20,min. Using electrokinetic supercharging, the sensitivity of the method was improved 1000-fold over a conventional injection under field-amplified sample stacking conditions with LODs of 180,ng/L. This is the first report of the separation of hypolipidaemics by CE. The developed method was validated and then applied to the determination of the target drugs in water samples from Hobart city. [source] Heart-cutting 2D-CE with on-line preconcentration for the chiral analysis of native amino acidsELECTROPHORESIS, Issue 6 2010Suzanne Anouti Abstract The use of transient moving chemical reaction boundary (tMCRB) was investigated for the on-line preconcentration of native amino acids in heart-cutting 2D-CE with multiple detection points using contactless conductivity detection. The tMCRB focusing was obtained by using ammonium formate (pH 8.56) as sample matrix and acetic acid (pH 2.3) as a BGE in the first dimension of the heart-cutting 2D-CE. Different experimental parameters such as the injected volume and the concentration in ammonium formate were optimized for improving the sensitivity of detection. A stacked fraction from the first dimension was selected, isolated in the capillary, and then separated in the second dimension in the presence of a chiral selector ((+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid). This on-line tMCRB preconcentration coupled with heart-cutting 2D-CE was applied with success to the chiral separation of D,L -phenylalanine, and D,L -threonine in a mixture of 22 native amino acids. The sample mixture was diluted in 0.8,M of ammonium formate, and injected at a concentration of 2.5,,M for each enantiomer with a volume corresponding to 10% of the total capillary volume. An LOD (S/N=3) of 2,,M was determined for L -threonine. [source] Novel negatively charged tentacle-type polymer coating for on-line preconcentration of proteins in CEELECTROPHORESIS, Issue 4 2009Liang Xu Abstract A novel negatively charged tentacle-type polymer-coated capillary column was fabricated and applied for on-line extraction and preconcentration of proteins. The polymer coating was prepared by glycidyl-methacrylate graft polymerization in a silanized capillary column and the following sulfonic acid group functionalization. It had high surface area and offered high phase ratio for protein adsorption. In addition, the polymer-coated capillary column provided more stable EOF than a bare uncoated capillary. These features of the polymer coating facilitated the extraction of proteins through electrostatic interactions. This was used to extract proteins. The extracted analytes were then desorbed and focused by EOF in the direction opposite to the sample injection flow for subsequent CE. With this procedure, over 1500-fold sensitivity enhancement was realized for myoglobin (MB) as compared with a normal capillary zone electrophoresis. By comparison of the peak areas of the enriched protein, it was found that the polymer-coated column could capture proteins about 30 times more than the uncoated column. In addition, the separation of a protein mixture containing 0.4,,g/mL of MB and 0.4,,g/mL of insulin was demonstrated by the on-line preconcentration and electrophoretic separation with the polymer-coated column. [source] On-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: A dual strategy for integrating sample pretreatment with chemical analysisELECTROPHORESIS, Issue 21 2005Adam S. Ptolemy Abstract Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho -phthalaldehyde/N -acetyl- L -cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector. [source] Chromotropic acid-functionalized polyurethane foam: A new sorbent for on-line preconcentration and determination of cobalt and nickel in lettuce samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006Valfredo Azevedo Lemos Abstract A chromotropic acid-functionalized polyurethane foam has been developed for use in an on-line preconcentration system for cobalt and nickel determination. The packing material was prepared by covalent coupling of chromotropic acid with the polyurethane foam through an azo group. Co and Ni ions were sorbed in the minicolumn, from which they could be eluted directly to the nebulizer-burner system of a flame atomic absorption spectrometer. Elution of cobalt and nickel from the minicolumn can be accomplished with 0.50 and 0.75 M HCl solutions, respectively. The enrichment factors obtained were 22 (Co) and 27 (Ni), for 60 s preconcentration time, and 57 (Co) and 59 (Ni), if a preconcentration time of 180 s was used. Under the optimum conditions, the proposed procedure allowed the determination of metals with detection limits of 0.43 (cobalt) and 0.52 ,g/L (nickel), respectively, on using preconcentration periods of 180 s. The accuracy of the developed procedure was evaluated by analysis of the certified reference materials NIST 1515 Apple Leaves and NIST 1570a Spinach Leaves. The method was applied to the analysis of lettuce samples. The contents of cobalt in the samples analyzed varied from 0.75 to 0.98 ,g/g. Nickel was not detected in the lettuce samples. [source] | ||||||||||