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1
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Simultaneous analysis of first-line anti-tuberculosis drugs in tablets by UV spectrophotometry compared to capillary zone electrophoresis

100%
Marcellos L., Faria A., Souza M., Almeida M., Sabin G., Poppi R., Oliveira M.
Open Chemistry
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2012
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vol. 10
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issue 6
1808-1816
EN
The development and optimization of a novel UV spectrophotometric methodology was proposed for simultaneous analysis of ethambutol (ETB), isoniazid (ISO), rifampicin (RIF) and pyrazinamide (PYR), using multivariate calibration based on the partial least squares method (PLS). The methodology was successfully applied for analysis of four-drug fixed dose combination (4-FDC) tablets used for tuberculosis treatment. A 34 Box-Behnken design, with triplicate in central point, was used for sample preparation in the calibration step. In the present case, nine latent variables were chosen for the model development that presented the smallest RMSECV and explain 98.76% of data variance in Y block (concentrations of ETB ISO, RIF and PYR) and 99.93% of data variance in X block (spectral data). PLS models for ETB, ISO, RIF and PYR presented RMSEP and R2 values of 0.23 mg L−1 and 0.971; 0.14 mg L−1 and 0.731; 0.11 mg L−1 and 0.990 and 0.57 mg L−1 and 0.972, respectively. A validation step was performed based on the comparison between the UV spectrophotometric proposed methodology and capillary zone electrophoresis (CZE) in 4-FDC real samples and no significant difference was found between two methodologies at 95% of confidence level. [...]
2
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Carbon nanotubes in capillary electrophoresis, capillary electrochromatography and microchip electrophoresis

100%
Pauwels J., Schepdael A.
Open Chemistry
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2012
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vol. 10
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issue 3
785-801
EN
Carbon nanotubes are among the plethora of novel nanostructures developed since the 1980s. Nanotubes have attracted considerable interest by the scientific community thanks to their extraordinary physical and chemical properties. Research areas have flourished in recent years and now include the nano-electronic, (bio)sensor and analytical field along with many others. This review covers applications of carbon nanotubes in capillary electrophoresis, capillary electrochromatography and microchip electrophoresis. First, carbon nanotubes and a range of electrophoretic techniques are briefly introduced and key references are mentioned. Next, a comprehensive survey of achievements in the field is presented and critically assessed. The merits and downsides of carbon nanotube addition to the various capillary electrophoretic modes are addressed. The different schemes for fabricating electrochromatographic stationary phases based on carbon nanotubes are discussed. Finally, some future perspectives are offered. [...]
3
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Separation of ketoprofen enantiomers at nanomolar concentration levels by micellar electrokinetic chromatography with on-line electrokinetic preconcentration

100%
Petr J., Ginterová P., Znaleziona J., Knob R., Lošťáková M., Maier V., Ševčík J.
Open Chemistry
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2013
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vol. 11
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issue 3
335-340
EN
Abstract Separation of enantiomers represents an extremely important task in the field of analytical chemistry. This paper contributes to the field of the on-line preconcentration of enantiomers by developing a novel setup based on the electrokinetic accumulation of ketoprofen enantiomers on the pH boundary followed by enantioselective mobilization by a mixture of SDS, sulfated-β-cyclodextrin (S-β-CD), and trimethyl-β-cyclodextrin (TM-β-CD). Under the best conditions, where the injection electrolyte was composed of 50 mmol L−1 borate/NaOH pH 9.5 with 60% (v/v) methanol, the background electrolyte contained 50 mmol L−1 phosphate/NaOH pH 2.5, and the mobilization electrolyte consisted of 50 mmol L−1 phosphate/NaOH pH 2.5 with 4.0% (w/v) S-β-CD, 0.5% (w/v) TM-β-CD, and 20 mmol L−1 SDS, the determination of nanomolar concentration levels of ketoprofen enantiomers was successful by using micellar electrokinetic chromatography with a common UV detection. LODs were 2.5 nmol L−1 and 3.4 nmol L−1, which represent enhancement factors of 9921 and 8529, respectively. The method was also applied to the determination of ketoprofen enantiomers in waste water samples by using simple filtration as a clean-up step. Here, the recovery of ketoprofen enantiomers was 91% at the concentration level of 5×10−9 mol L−1. Graphical abstract [...]
4
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Recent progress for capillary electrophoresis with electrochemical detection

100%
Yu H., Xu X., Sun J., You T.
Open Chemistry
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2012
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vol. 10
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issue 3
639-651
EN
Capillary electrophoresis (CE) is an attractive technique in separation science because of its high separation performance, short analysis time and low cost. Electrochemical detection (EC) is a powerful tool for CE because of its high sensitivity. In this review, developments of CE-EC from 2008 to August, 2011 are reviewed. We choose papers of innovative and novel results to demonstrate the newest and most important progress in CE-EC. [...]
5
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Interfacing a microchip-based capillary electrophoresis system with a microwave induced plasma spectrometry for copper speciation

88%
Matusiewicz H., Ślachciński M.
Open Chemistry
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2011
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vol. 9
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issue 5
896-903
EN
A microchip-based capillary electrophoresis (µCE) system was interfaced with a microwave induced plasma optical emission spectrometry (MIP-OES) to provide copper species separation capabilities. This system uses an extremely low flow demountable direct injection high efficiency nebulizer (D-DIHEN) sited directly at the liquid exit of the chip. A supplementary flow of buffer solution at the channel exit was used to improve nebulization efficiency. A small evaporation chamber has been incorporated into the interface in order to prevent the losses associated with traditional spray chambers, allowing the entire aerosol sample to enter the plasma. Syringe pumps were used to manipulate the flow rate and flow direction of the sample, buffer, and supplementary buffer solution. Sample volumes of 25 nL can be analyzed. With application of an electric field up to 500 V cm−1, species such as Cu(II) and Cu(EDTA)2− were separated in acidic solution within 90 s using a 26 mm long separation channel etched in a glass base. Resolution of the Cu(II) and Cu(EDTA)2− peaks was 1.1 using the chip-based µCE-MIP-OES system. [...]
6
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Determination of phenolic acids by capillary zone electrophoresis and HPLC

88%
Kvasnička F., Čopíková J., Ševčík R., Krátká J., Syntytsia A., Voldřich M.
Open Chemistry
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2008
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vol. 6
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issue 3
410-418
EN
Selected phenolic acids are determined by capillary zone electrophoresis and HPLC, each using UV detection. The optimised CZE background electrolyte contained 50 mM acetic acid, 95 mM 6-aminocaproic acid, 0.1% polyacrylamide, 1% polyvinylpyrrolidone, and 10% methanol. Twelve phenolic acids (gallic, p-hydroxybenzoic, 3,4-dihydroxybenzoic, vanillic, syringic, o-coumaric, p-coumaric, caffeic, sinapic, ferulic, salicylic and chlorogenic) were separated within 10 minutes. Chromatographic separation of these phenolic acids was carried out on an Eclipse XBD C8 column using a mobile phase gradient (acetonitrile / methanol / water / 0.1% phosphoric acid); all were separated within 25 minutes. Electrophoretic and chromatographic determinations of ferulic and chlorogenic acids were compared on barley, malt, and potato samples. The methods’ characteristics were: linearity (1–20 mg ml and 0.2–4 mg ml−1), accuracy (recovery 94 ± 5% and 96 ± 4%), intra-assay repeatability (4.1% and 3.5%), and detection limit (0.2 and 0.02 mg ml−1). [...]
7
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Recentchiral selectors for separation in HPLC and CE

88%
Kalíková K., Riesová M., Tesařová E.
Open Chemistry
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2012
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vol. 10
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issue 3
450-471
EN
Enantiomers (stereoisomers) can exhibit substantially different properties if present in chiral environments. Since chirality is a basic property of nature, the different behaviors of the individual enantiomers must be carefully studied and properly treated. Therefore, enantioselective separations are a very important part of separation science. To achieve the separation of enantiomers, an enantioselective environment must be created by the addition of a chiral selector to the separation system. Many chiral selectors have been designed and used in various fields, such as the analyses of drugs, food constituents and agrochemicals. The most popular have become the chiral selectors and/or chiral stationary phases that are of general use, i.e., are applicable in various separation systems and allow for chiral separation of structurally different compounds. This review covers the most important chiral selectors / chiral stationary phases described and applied in high performance liquid chromatography and capillary electrophoresis during the period of the last three years (2008–2011). [...]
8
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Characterization of CdSe quantum dots with bidentate ligands by capillary electrophoresis

88%
Oszwałdowski S., Zawistowska-Gibuła K., Roberts K.
Open Chemistry
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2011
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vol. 9
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issue 4
572-584
EN
The CdSe quantum dots (QDs) with bidentate ligands: a-diimine (NN) and dihydrolipoic acid (DHLA) were synthesized and characterized by UV-Vis, particle size and capillary electrophoretic techniques. Two systems were analyzed: CdSe with one ligand (CdSe/ligand) and CdSe with two different ligands (CdSe//ligand1/ligand2), where ligand = α-diimine or DHLA. Hydrodynamic features of functionalized QDs were characterized by zone capillary electrophoretic (CZE), and particle size techniques and these methods were consistent. It was established that CZE, micellar (MEKC) and microemulsion (MEEKC) modes were suitable for separating charged CdSe QDs and that no peaks were obtained for QDs passivated with electrically neutral ligands. For CdSe QDs with neutral (NN) ligands, a preconcentration method with the use of a micellar plug was introduced for visualizing these QDs. A sharp peak representing neutral QDs was obtained within the zone of micellar plug of a non-ionic surfactant, Here, a ligand character used for CdSe modification and the type of the electrophoretic method applied were the determining factors for the QDs peak visualization. Moreover, examples of visualization of charged and neutral QDs on the same run were presented, and for this purpose, dual mechanism (separation/preconcentration) was proposed. [...]
9
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Separation and determination of inorganic cations in beverages by capillary electrophoresis with indirect UV detection

88%
Gao J., Fan H., Yang W., Sun X., Li C., Mao X., Wang J., Wang R., Jia Z.
Open Chemistry
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2008
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vol. 6
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issue 4
617-621
EN
A rapid, simple and reliable capillary electrophoresis method for the separation and quantitation of inorganic cations with indirect UV detection at 214 nm was developed. The electrolyte was: 12 mM imidazole as background absorbance provider; 5 mM malic acid and 1.0 mM 18-crown-6 ether as complexing agents; and 20% D2O (v/v) to improve ion mobility. The pH was 4.25. The applied voltage was 22 kV at 22°C. Nine ions were completely separated and determined with correlation coefficients of 0.9979-0.9992. The relative standard deviations (RSD) were less than 0.5% for migration time and less than 5.2% for peak area (n=8). The detection limits (S/N=3) were from 0.08 mg L−1 (for Na+) to 0.51 mg L−1 (for Cu2+). To assess the reliability atomic absorption (AA) was also used to determine the same samples. Satisfactory results were obtained for real samples of jasmine tea drink and coconut milk. [...]
10
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Capillary electrophoretic separation and characterizations of CdSe quantum dots

88%
Oszwałdowski S., Zawistowska K., Grigsby L., Roberts K.
Open Chemistry
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2010
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vol. 8
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issue 4
806-819
EN
We have developed a capillary electrophoresis method to characterize the QD surface ligand interactions with various surfactant systems. The method was demonstrated with 2–5 nm CdSe nanoparticles surface-passivated with trioctylphosphine oxide (TOPO). Water solubility was accomplished by surfactant-assisted phase transfer via an oil-in-water microemulsion using either cationic, anionic, or non-ionic surfactants. Interaction between the QD surface ligand (TOPO) and the alkyl chain of the surfactant molecule produces a complex and dynamic surface coating that can be characterized through manipulation of CE separation buffer composition and capillary surface modification. Additional characterization of the QD surface ligand interactions with surfactants was accomplished by UV-VIS spectroscopy, photoluminescence, and TEM. It is anticipated that studies such as these will elucidate the dynamics of QD surface ligand modifications for use in sensors. [...]
11
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Review of recent developments of on-line sample stacking techniques and their application in capillary electrophoresis

75%
Chen Y., Lü W., Chen X., Teng M.
Open Chemistry
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2012
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vol. 10
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issue 3
611-638
EN
Capillary electrophoresis (CE) has become one of the most useful tools in separation science because of its high separation efficiency, low cost, versatility, ease of sample preparation and automation. However, some limitations of CE, such as poor concentration sensitivity due to its lower sample loading and shorter optical path length, limits its further applications in separation science. In order to solve this problem, various on-line sample preconcentration techniques such as transient isotachophoresis preconcentration, field-enhanced sample stacking, micelle to solvent stacking, micelle collapse, dynamic pH junction, sweeping, solid phase extraction, single drop microextraction and liquid phase microextraction have been combined with CE. Recent developments, applications and some variants together with different combinations of these techniques integrating in CE are reviewed here and our discussions will be confined to the past three years (2008–2011). [...]
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