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• A methodology for designing iEK systems for separating tertiary samples is presented. • The methodology is designed for complex samples, illusterating versatility. • Microchannels with varied shapes and arrangements of insulating posts were explored. • COMSOL model predicted the retention time of particles to identify the best designs. • Experimentally tested channel designs separated tertiary mixtures efficiently. This study presents a methodology for designing effective insulator-based electrokinetic (iEK) systems for separating tertiary microparticle samples, which can be extended to more complex samples. First, 144 distinct iEK microchannel designs were built considering different shapes and arrangements of the insulating posts. Second, a mathematical model was developed with COMSOL software to predict the retention time of each particle type in the microchannel, this allowed identifying the best channel designs for two distinct types of separations: charge-based and sized-based. Third, the experimental charge-based and size-based separations of the tertiary microparticle mixtures were performed employing the improved designs identified with COMSOL modeling. The experimental results demonstrated successful separation in terms of separation resolution and good agreement with COMSOL predictions. The findings from this study show that the proposed method for device design, which combines mathematical modeling with varying post shape and post arrangement is an effective approach for identifying iEK systems capable of separating complex microparticle samples. [Display omitted] [ABSTRACT FROM AUTHOR]

• Presents the first assessment of the nonlinear electrophoretic migration of non-spherical bacterial and yeast cells. • Employs the three-dimensional parameter of sphericity to quantify cell shape in terms of deviation from a perfect sphere. • Estimates the mobility of nonlinear electrophoretic migration of cells considering two distinct electric field regimes: the moderate electric field regime (cubic dependance) and the strong electric field regime (3/2 dependance). • Describes the effect of cell size and cell shape on the magnitudes of the mobilities of nonlinear electrophoresis under the moderate and strong electric field regimes. This study contributes to the renewed interest in the study of nonlinear electrophoresis of colloidal particles. In this work the influence of cell shape on electrophoretic migration under the nonlinear regimes of moderate and strong field regimes was assessed. Four types of bacterial and yeast cells (one spherical, three non-spherical) were studied and their electrophoretic mobilities for the moderate and strong electric field magnitude regimes were estimated experimentally. The parameter of sphericity was employed to assess the effect cell shape on the nonlinear electrophoresis migration velocity and corresponding mobility under the two electric field magnitude regimes studied. As particle migration under nonlinear electrophoresis depends on particle size and shape, the results in terms of mobilities of nonlinear electrophoresis were presented as function of cell hydrodynamic diameter and sphericity. The results indicated that the magnitude of the mobilities of nonlinear electrophoresis for cells increase with increasing cell size and increase with increasing deviations from spherical shape, which is indicated by lower sphericity values. The results presented here are the very first assessment of the two types of mobilities of nonlinear electrophoresis of cells as a function of size and shape. [ABSTRACT FROM AUTHOR]

• Tracking water-soluble oligomers in latex serum by capillary electrophoresis. • Distribution of residual surfactants in serum is different from raw surfactant. • Separation of water soluble oligomers in serum by CE using indirect UV detection. • Putative chemical structures of oligomers based on electrophoretic mobility modeling. • Characterization of latexes by Capillary electrophoresis using serum as electrolyte. The characterization of hydrosoluble oligomers in latexes is an important topic in emulsion polymerization since oligomers are suspected to be responsible for latex destabilization. In this work, the hydrosoluble fraction of poly(vinylidene chloride) latexes synthesized by emulsion polymerization of three monomers (acrylic acid, methyl acrylate, vinylidene chloride) was characterized by capillary electrophoresis (CE). CE using direct UV detection permitted to estimate residual monomers and surfactants concentrations contained in the latexes serums. Water soluble oligomers, polymerization initiator (persulfate) and other inorganic anions were detected by indirect UV detection. The oligomers content in the dry extract of serum was estimated to be about 6% (% m/m) represented mainly by 9 different compounds belonging to 3 different families. Using a semi-empirical electrophoretic mobility modeling, the charge number of these oligomers was estimated to be −2 and the molar masses were estimated in the range of ∼300–550 g.mol−1. Oligomer samples obtained by surfactant-free polymerization, with different initial monomers proportions, provided qualitatively 14 different oligomers, including the 9 oligomers previously detected in the serums. Finally, the latex was characterized (electrophoretic mobility and zeta potential) using its serum as a background electrolyte. This approach could be very useful to study the behavior of the latexes, and possibly destabilization effect, in analytical conditions very close to its real environment / applications. [ABSTRACT FROM AUTHOR]

Highlights • Sensitive and reliable electrophoretic method. • Direct determination of histamine without derivatization step. • Comparable results as HPLC method with fluorimetric detection. • Complementary alternative method to HPLC. Abstract An electrophoretic method (on-line coupled capillary isotachophoresis with capillary zone electrophoresis) with conductometric detection (cITP-CZE-COND) for the determination of histamine in foodstuffs and feedstuffs is described. Under optimised conditions in cationic mode the histamine is well separated from other components of acidic sample extract and detected by conductimeter within 25 min. Method characteristics, i.e. , linearity (22–222 ng/mL), accuracy (recovery 91 ± 9%), repeatability (1.5%), reproducibility (3.4%), and detection limit (4 ng/mL) were evaluated. On a representative series of 37 food and feed samples it has been shown that the cITP-CZE-COND gives comparable results as routine accredited HPLC method. Low laboriousness, high sensitivity, speed of analysis, and low running cost are important attributes of cITP-CZE-COND. [ABSTRACT FROM AUTHOR]

Highlights • PolyDOPA-MNPs are prepared and used as adsorbents in MSPE to extract ofloxacin. • The extraction process includes 2 min adsorption and 2 min desorption. • PA-FESI is used to improve the detection sensitivity of ofloxacin enantiomers. • MSPE/PA-FESI CE method is used to determine ofloxacin enantiomers in urine/blood. • The detection limit of each ofloxacin enantiomer is 0.29 ng/mL. Abstract Chiral separation of low concentrations of pharmaceuticals in biofluids is a challenge task. In this study, a method is developed to enantioseparate trace amount of racemic ofloxacin in urine and bovine blood by combining magnetic solid phase extraction (MSPE) and chiral capillary electrophoresis (CE). Poly(3,4-dihydroxyphenylalanine) modified magnetic nanoparticles (polyDOPA-MNPs) are prepared and used as the adsorbents in MSPE to extract ofloxacin. The polyDOPA-MNPs are spherical, about 130 nm in diameter and the polyDOPA shell is about 3 nm. The extraction process of polyDOPA-MNPs for ofloxacin includes 2 min adsorption and 2 min desorption with the assistance of sonication. Under the optimized MSPE conditions (3 mg polyDOPA-MNPs as adsorbents, sample pH 7.0, 75% (v/v) AcOH in methanol as eluent, adsorption time 2 min, desorption time 2 min), the extraction efficiency of ofloxacin is 95%. In chiral CE, pressure-assisted field-enhanced sample injection (PA-FESI) is developed to improve the detection sensitivity of ofloxacin enantiomers. The MSPE/PA-FESI chiral CE method demonstrates a good linearity in the concentration range of 0.01–0.06 μg/mL, with a detection limit as low as 0.29 ng/mL. The feasibility of the method is verified by the successful determination of trace amounts of ofloxacin enantiomers in spiked urine and bovine blood samples. [ABSTRACT FROM AUTHOR]

Deterministic Lateral Displacement (DLD) exploits periodic arrays of pillars inside microfluidic channels for high-precision sorting of micro- and nano-particles. Previously we demonstrated how DLD separation can be significantly improved by the addition of AC electrokinetic forces, increasing the tunability of the technique and expanding the range of applications. At high frequencies of the electric field (>1 kHz) the behaviour of such systems is dominated by Dielectrophoresis (DEP), whereas at low frequencies the particle behaviour is much richer and more complex. In this article, we present a detailed numerical analysis of the mechanisms governing particle motion in a DLD micropillar array in the presence of a low-frequency AC electric field. We show how a combination of Electrophoresis (EP) and Concentration-Polarisation Electroosmosis (CPEO) driven wall-particle repulsion account for the observed experimental behaviour of particles, and demonstrate how this complete model can predict conditions that lead to electrically induced deviation of particles much smaller than the critical size of the DLD array. • Low frequency electrokinetics improves Deterministic Lateral Displacement separation. • CPEO driven wall-repulsion plays a major role in this mechanism. • Combination of Electrophoresis and CPEO fully explains the low frequency separation. • The mechanism of Electrokinetic biased DLD separation has been fully characterized. • This model enables numerical optimization of future electrokinetic DLD devices. [ABSTRACT FROM AUTHOR]

• Recent advances in paper/thread-based zone and capillary electrophoresis techniques. • Various sample pretreatment methods using electrophoresis on wicking substrates. • Review of unmodified and modified microfluidic paper/threat -based chromatography. • Application of paper/threat -based chromatography in blood separation. Paper and thread are widely used as the substrates for fabricating low-cost, disposable, and portable microfluidic analytical devices used in clinical, environmental, and food safety monitoring. Concerning separation methods including chromatography and electrophoresis, these substrates provide unique platforms for developing portable devices. This review focuses on summarizing recent research on the miniaturization of the separation techniques using paper and thread. Preconcentration, purification, desalination, and separation of various analytes are achievable using electrophoresis and chromatography methods integrated with modified or unmodified paper/thread wicking channels. A variety of 2D and 3D designs of paper/thread platforms for zone electrophoresis, capillary electrophoresis, and modified/unmodified chromatography are discussed with emphasis on their limitation and improvements. The current progress in the signal amplification strategies such as isoelectric focusing, isotachophoresis, ion concentration polarization, isoelectric focusing, and stacking methods in paper-based devices are reviewed. Different strategies for chromatographic separations based on paper/thread will be explained. The separation of target species from complex samples and their determination by integration with other analytical methods like spectroscopy and electrochemistry are well-listed. Furthermore, the innovations for plasma and cell separation from blood as an important human biofluid are presented, and the related paper/thread modification methods are explored. [ABSTRACT FROM AUTHOR]

A capillary electrophoresis method for the simultaneous determination of the enantiomeric purity and of impurities of the chiral calcimimetic drug cinacalcet hydrochloride has been developed following Quality by Design principles. The scouting phase was aimed to select the separation operative mode and to identify a suitable chiral selector. Among the tested cyclodextrins, (2-carboxyethyl)-β-cyclodextrin and (2-hydroxypropyl)-γ-cyclodextrin (HPγCyD) showed good chiral resolving capabilities. The selected separation system was solvent-modified capillary zone electrophoresis with the addition of HPγCyD and methanol. Voltage, buffer pH, methanol concentration and HPγCyD concentration were investigated as critical method parameters by a multivariate strategy. Critical method attributes were represented by enantioresolution and analysis time. A Box-Behnken Design allowed the contour plots to be drawn and quadratic and interaction effects to be highlighted. The Method Operable Design Region (MODR) was identified by applying Monte-Carlo simulations and corresponded to the multidimensional zone where both the critical method attributes fulfilled the requirements with a desired probability π ≥ 90%. The working conditions, with the MODR limits, corresponded to the following: capillary length, 48.5 cm; temperature, 18 °C; voltage, 26 kV (26–27 kV); background electrolyte, 150 mM phosphate buffer pH 2.70 (2.60–2.80), 3.1 mM (3.0–3.5 mM) HPγCyD; 2.00% (0.00–8.40%) v/v methanol. Robustness testing was carried out by a Plackett-Burman matrix and finally a method control strategy was defined. The complete separation of the analytes was obtained in about 10 min. The method was validated following the International Council for Harmonisation guidelines and was applied for the analysis of a real sample of cinacalcet hydrochloride tablets. [ABSTRACT FROM AUTHOR]

The enantioseparation of the non-protein amino acid homocysteine by CE was investigated in this article using eleven neutral CDs and five chiral ionic liquids as chiral selectors. Using a previous derivatization step with FMOC and the subsequent separation under neutral conditions, homocysteine enantiomers were only separated when γ-CD or (R)-N,N,N-trimethyl-2-aminobutanol-bis(trifluoromethane-sulfon)imidate (EtCholNTf 2 ) were employed as sole chiral selectors in the separation buffer. On the one hand, γ-CD gave rise to the enantiomeric separation in 10 min with a resolution value of 1.9, whereas EtCholNTf 2 let to obtain a resolution value of 1.4 in more than 50 min. Then, the evaluation of the combined use of both selectors was also carried out, resulting in a considerable increase in the Rs. The best enantioseparation for homocysteine was obtained when 10 mM EtCholNTf 2 was added to 50 mM phosphate buffer (pH 7.0) containing 2 mM γ-CD. In an attempt to discriminate specific chiral cation effect from the salt effect, the influence of adding LiNTf 2 to the separation medium was also evaluated, resulting in lower resolution values for homocysteine when compared to those achieved with the addition of EtCholNTf 2 , indicating a synergistic effect between EtCholNTf 2 and γ-CD. Interestingly, the enantiomer migration order changed depending on the use of a single chiral selector or dual systems. When EtCholNTf 2 or γ-CD were employed as sole chiral selectors, D-enantiomer was the first-migrating enantiomer. However, an inversion in the migration order was observed when both selectors were combined in a dual system being the L-enantiomer the first-migrating one. [ABSTRACT FROM AUTHOR]

Two novel periodic mesoporous organosilica materials were synthesized with a neutral phenylene-bridged ligand, 1,4-bis(trimethoxysilylethyl)benzene, one of them using tetraethyl orthosilicate as additional silica source (PMO-TMSEB-1 and PMO-TMSEB-2). A third material was also synthesized with 1,4-bis(triethoxysilyl)benzene ligand (PMO-TESB-1) which use has scarcely been reported. The three materials were evaluated as solid-phase extraction (SPE) sorbents for the off-line extraction of a mixture of seven drugs of different nature (duloxetine, terbutaline, econazole, propranolol, verapamil, metoprolol, and betaxolol) from water samples. Subsequent simultaneous enantiomeric analysis by CE, using sulfated-β-cyclodextrin (2% w/v) dissolved in a 25 mM phosphate buffer (pH 3.0) and a voltage of −20 kV (negative polarity) was carried out. Enantiomeric resolutions ranging from 2.4 to 8.5 were obtained in an analysis time of 16 min. After optimization of SPE parameters, it was shown that using just 100 mg of PMO-TESB-1 as sorbent, a preconcentration factor of 400 with 200 mL solution was achieved, allowing recoveries between 80.5 and 103.1% (except for terbutaline), with good repeatability (% RSD = 2–8 %, n = 5). Analytical characteristics of the method were evaluated in terms of precision, linearity and accuracy with method quantitation limits between 5.6 and 21.9 μg/L. The developed method was applied to the analysis of spiked wastewater samples collected in different treatment plants, with recoveries between 73.9 and 102.9% except for econazole with recovery values ranging between 58.5 and 72.4%. [ABSTRACT FROM AUTHOR]

Two novel materials based on periodic mesoporous organosilica (PMO) with cationic amine-bridged ligands, (styrylmethyl)bis(triethoxysilylpropyl)ammonium chloride (PMO-STPA) and bis(3-triethoxysilylpropyl)amine (PMO-TEPA), were synthesized in this work to obtain materials with reverse-phase/strong anionic exchange mixed-mode or strong anionic exchange retention mechanism, respectively. The resulting materials were comprehensively characterized and showed functionalization with cationic amine-bridged ligands, and values of surface areas characteristic of mesoporous materials (higher than 100 m 2 /g). These materials were evaluated for the off-line solid-phase extraction (SPE) of a mixture of six phenoxy acid herbicides (fenoprop, mecoprop, dichlorprop, 2-(4-chlorophenoxy)propionic acid (4-CPPA), 2-(3-chlorophenoxy)propionic acid (3-CPPA), 2-phenoxypropionic acid (2-PPA)) from water samples previous to their analysis by CE with diode-array detection using a dual chiral selector system (20 mM of heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD) and 7 mM of (2-hydroxypropyl)-β-CD (HP-β-CD) dissolved in 50 mM phosphate buffer, pH 7.0) which enabled the simultaneous enantiomeric separation of the six phenoxy acid herbicides in 11 min. SPE parameters were optimized and recoveries obtained for PMO-STPA and PMO-TEPA sorbents were compared. Under the optimized conditions, it was demonstrated that using 100 mg of PMO-STPA sorbent, a maximum preconcentration factor (PF) of 1500 was achieved with 750 mL of standard solution, allowing recoveries between 75.5 and 112.2%, with good repeatability (RSD = 1.9–8.7%, n = 6). Analytical characteristics of the method were evaluated in terms of precision, linearity and accuracy with method quantitation limits (MQL) between 0.4 and 14.3 μg/L. The developed method was applied to the analysis of river samples and effluents from wastewater treatment plants, with recoveries ranging from 78.3 to 107.5%. [ABSTRACT FROM AUTHOR]

The migration behavior of organic fluorescent dyes (i.e., crystal violet, methyl violet base, methyl violet B base, rhodamine 6G, and rhodamine B base) in non-aqueous capillary electrophoresis (NACE) was investigated by focusing on the physicochemical properties of various organic solvents [ethanol, methanol, 2-propanol, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO)] in background electrolyte (BGE). Laser-induced fluorescence (LIF) and UV/Vis detectors were employed to observe both the migration time of organic dyes and the electroosmotic flow (EOF) in NACE, respectively. As seen in conventional aqueous BGE, the mobility of EOF in organic solvents tended to rise when the ratio between the dielectric constant and the solvent’s viscosity ( ε / η ) increased in accordance with Smoluchowski’s equation. However, unlike the ε / η of pure organic solvents, the migration order of dyes changed as follows: methanol (60.0) > DMF (45.8) > ethanol (22.8) > DMSO (23.4) > 2-propanol (9.8). Since the amount of acetic acid added to balance the pH depends on the p K a of each solvent, EOF changed when the difference in the ε / η value was small. This resulted from the inhibition of mobility, and its difference was dependent on the ε / η of BGEs with high ionic strength. In particular, the actual mobility of dyes in DMF showed excellent compliance with the Debye–Hückel–Onsager (DHO) theory extended by Falkenhagen and Pitts, which enabled us to analyze all dyes within 15 min with excellent resolution ( R s >  2.5) under optimum NACE conditions (10 mM sodium borate and 4661 mM acetic acid in 100% DMF, pH 4.5). In addition, the NACE method was successfully applied for analyzing commercially available ballpoint ink pens. Thus, these results could be used to anticipate the migration order of organic dyes in a 100% NACE separation system. [ABSTRACT FROM AUTHOR]

The labeling by amino acids and peptides was investigated for sensitive and fast analyses of oligosaccharides and N -linked glycans by capillary electrophoresis-mass spectrometry (CE-MS). Peptide tags with a various number of histidine residues were tested for maltooligosaccharide labeling in order to investigate the effect of the size of labels and a number of charges on CE-MS analysis. Nevertheless, the reductive amination labeling of N -linked glycans by a hexahistidine tag resulted in a multiple products formation, therefore a peptide tag was modified by hydrazine functionality in order to perform labeling by hydrazone formation chemistry. This labeling approach significantly improved sensitivity with LOD of labeled maltopentaose determined to be 40 nmol/L and also significantly reduced separation time of neutral maltooligosaccharides and N -linked glycans released from bovine ribonuclease B. Furthermore, the labeling by this multi-cationic peptide hydrazine tag also allowed performing analysis of acidic glycans by CE-MS in a positive ion mode as demonstrated by separation of sialylated N -linked glycans released from bovine fetuin. [ABSTRACT FROM AUTHOR]

Dielectrophoresis (DEP), the migration of particles due to polarization effects under the influence of a nonuniform electric field, was employed for characterizing the behavior and achieving the separation of larger (diameter >5 μm) microparticles by exploiting differences in electrical charge. Usually, electrophoresis (EP) is the method of choice for separating particles based on differences in electrical charge; however, larger particles, which have low electrophoretic mobilities, cannot be easily separated with EP-based techniques. This study presents an alternative for the characterization, assessment, and separation of larger microparticles, where charge differences are exploited with DEP instead of EP. Polystyrene microparticles with sizes varying from 5 to 10 μm were characterized employing microdevices for insulator-based dielectrophoresis (iDEP). Particles within an iDEP microchannel were exposed simultaneously to DEP, EP, and electroosmotic (EO) forces. The electrokinetic behavior of four distinct types of microparticles was carefully characterized by means of velocimetry and dielectrophoretic capture assessments. As a final step, a dielectropherogram separation of two distinct types of 10 μm particles was devised by first characterizing the particles and then performing the separation. The two types of 10 μm particles were eluted from the iDEP device as two separate peaks of enriched particles in less than 80 s. It was demonstrated that particles with the same size, shape, surface functionalization, and made from the same bulk material can be separated with iDEP by exploiting slight differences in the magnitude of particle charge. The results from this study open the possibility for iDEP to be used as a technique for the assessment and separation of biological cells that have very similar characteristics (shape, size, similar make-up), but slight variance in surface electrical charge. [ABSTRACT FROM AUTHOR]

The modeling and simulation software COMSOL Multiphysics ® was recently extended with an electrophoretic transport interface. Its performance was investigated by comparison to results obtained using the 1D dynamic electrophoresis simulators GENTRANS and SIMUL5. Simulations of zone electrophoresis, isotachophoresis, isoelectric focusing and of an oscillating electrolyte system were performed. Smooth profiles were essentially identical indicating that the COMSOL electrophoretic transport interface is able to reproduce results of the 1D simulators. Differences in the way the respective numerical schemes handle steep concentration gradients and associated instabilities were observed. The COMSOL electrophoretic transport interface is expected to be useful as a general model for simulations in 1D, 2D or 3D geometries, as well as for simulations combining electrophoresis with other physical phenomena. [ABSTRACT FROM AUTHOR]

Elastase, collagenase, hyaluronidase and tyrosinase, are very interesting enzymes due to their direct implication in skin aging and as therapeutic hits. Different techniques can be used to study these enzymes and to evaluate the influence of effectors on their kinetics. Nowadays, analytical techniques have become frequently used tools for miniaturizing enzyme assays. The main intention of this article is to review chromatographic and electrophoretic tools that study the four enzymes above mentioned. More specifically, the use of high-performance liquid chromatography and capillary electrophoresis and their derivative techniques for monitoring these enzymes will be investigated. The advantages and limitations of these assays will also be discussed. The original use of microscale thermophoresis and thin layer chromatography in this domain will also be covered. [ABSTRACT FROM AUTHOR]

The main purpose of the present work is to provide a fully integrated miniaturized electrophoretic methodology in order to facilitate the quality control of monoclonal antibodies (mAbs). This methodology called D-PES, which stands for Diffusion-mediated Proteolysis combined with an Electrophoretic Separation, permits to perform subsequently mAb tryptic digestion and electrophoresis separation of proteolysis products in an automated manner. Tryptic digestion conditions were optimized regarding the influence of enzyme concentration and incubation time in order to achieve similar enzymatic digestion efficiency to that obtained with the classical methodology (off-line). Then, the optimization of electrophoretic separation conditions concerning the nature of background electrolyte (BGE), ionic strength and pH was realized. Successful and repeatable electrophoretic profiles of three mAbs digests (Trastuzumab, Infliximab and Tocilizumab), comparable to the off-line digestion profiles, were obtained demonstrating the feasibility and robustness of the proposed methodology. In summary, the use of the proposed and optimized in-line approach opens a new, fast and easy way for the quality control of mAbs. [ABSTRACT FROM AUTHOR]

Alzheimer’s disease is the most common cause of dementia, afflicting over 34 million patients worldwide. Since β-secretase is a rate-limiting enzyme of the production of neurotoxic β-amyloid peptide oligomers abnormally accumulated in the affected brain tissue, its specific inhibition appears to be a promising approach to slowing down or even stopping the progression of the disease. Hence two on-line capillary electrophoretic methods for studies of β-secretase activity based on the principles of transverse diffusion of laminar flow profiles and electrophoretically mediated microanalysis were developed, both using a simple unlabeled peptide substrate and UV detection. The optimized procedures were thoroughly validated and applied for determining the enzyme’s kinetic parameters and the inhibition characteristics of two potent probe inhibitors. The resulting values were found to be comparable to literature data obtained with other analytical techniques. The suitability of the employed methodologies for different experimental designs is discussed on the basis of a statistical evaluation of the experimental data. The presented methods constitute a miniaturized and fully automated tool, which should be suitable for kinetic and inhibition studies of β-secretase as a target for Alzheimer’s disease drug discovery in the early stages of the development of a new drug. [ABSTRACT FROM AUTHOR]

An electrophoretic method (on-line coupled capillary isotachophoresis with capillary zone electrophoresis with conductometric detection (cITP-CZE-COND)) for the determination of chitin in insects based on the analysis of glucosamine after acidic hydrolysis of the sample is described. Chitin is deacetylated and hydrolyzed to glucosamine by acidic hydrolysis (6 M sulfuric acid, 110 °C, 6 h). Under optimized electrophoresis conditions, glucosamine (GlcN) is separated from other sample components in cationic mode and detected with a conductometer within 15 min. The performance method characteristics of the GlcN assay, i.e. , linearity (0.2–20 μmol), accuracy (103 ± 5%), repeatability (1.9%), reproducibility (3.4%), limits of detection (0.06 μmol/L) and quantification (0.2 μmol/L), were evaluated. On a series of 28 insect samples, it was proven that cITP-CZE-COND provides results of chitin content in insects comparable to the literature data. The important features of the developed cITP-CZE-COND method are easy sample treatment, high sensitivity and selectivity, and low running costs. It is clear from the above that the cITP-CZE-COND method is suitable for analysis of insect samples for chitin content. [ABSTRACT FROM AUTHOR]

The aim of this article is to study the modification of an inner capillary wall with sol–gel coating (pure silica sol–gel or silica sol–gel containing porphyrin-brucine conjugate) and determine its influence on the separation process using capillary electrophoresis/electrochromatography method. After modification of the inner capillary surface the separation of analytes was performed using two different phosphate buffers (pH 2.5 and 9.0) and finally the changes in electrophoretic mobilities of various samples were calculated. To confirm that the modification of the inner capillary surface was successful, the parts of the inner surfaces of capillaries were observed using scanning electron microscopy. The analytes used as testing samples were oligopeptides, nucleosides, nucleobases and finally nucleotides. [ABSTRACT FROM AUTHOR]

In this work, we developed the model and theory of free-flow moving reaction boundary electrophoresis (FFMRB) for continuous protein concentration for the first time. The theoretical results indicated that (i) the moving reaction boundary (MRB) can be quantitatively designed in free-flow electrophoresis (FFE) system; (ii) charge-to-mass ratio (Z/M) analysis could provide guidance for protein concentration optimization; and (iii) the maximum processing capacity could be predicted. To demonstrate the model and theory, three model proteins of hemoglobin (Hb), cytochrome C (Cyt C) and C-phycocyanin (C-PC) were chosen for the experiments. The experimental results verified that (i) stable MRBs with different velocities could be established in FFE apparatus with weak acid/weak base neutralization reaction system; (ii) proteins of Hb, Cyt C and C-PC were well concentrated with FFMRB; and (iii) a maximum processing capacity and recovery ratio of Cyt C enrichment were 126 mL/h and 95.5% respectively, and a maximum enrichment factor was achieved 12.6 times for Hb. All of the experiments demonstrated the protein concentration model and theory. In contrast to other methods, the continuous processing ability enables FFMRB to efficiently enrich diluted protein or peptide in large volume solution. [ABSTRACT FROM AUTHOR]

Amino acids are crucial compounds involved in most biochemical processes essential for life. Since their dynamic turnover reflects the actual physiology of the cell/organism, a turnover assessment may provide valuable information related to multiple physiological and pathophysiological conditions. The sensitive determination of amino acids is predominantly associated with their derivatization which might be laborious, time-consuming and difficult to standardize. However, capillary electrophoresis offers the automatic injection and mixing of reactants, incubation of the reaction mixture, separation and detection of the reaction products in one on-capillary procedure. Among the on-capillary mixing strategies, electrophoretically mediated microanalysis (EMMA) is superior in terms of mixing efficiency. In this paper, we present an optimization of EMMA for the simultaneous derivatization of standard amino acids by naphthalene-2,3-dicarboxaldehyde/NaCN and its application to targeted human embryo metabolomics. For such a purpose, novel separation conditions were developed involving the background electrolyte, comprised of 73 mM sodium dodecyl sulfate, 6.7 % (v/v) 1-propanol, 0.5 mM (2-hydroxypropyl)-β-cyclodextrin and 135 mM boric acid/sodium hydroxide buffer (pH 9.00). Finally, the optimized EMMA was compared to a fundamentally different mixing strategy, namely the transverse diffusion of laminar flow profiles, and proved to be also suitable for human plasma analysis. [ABSTRACT FROM AUTHOR]

The orthogonal pressurized planar electrochromatography (OPPEC) is an example of 2-D separation technique, in which two simultaneous and orthogonal processes of electrophoresis and chromatography are involved in the separation mechanism. In the case of preparative separation of substances characterized by different electrophoretic mobility, such separation system can be constantly fed with the sample solution and the separated components can be constantly collected at its outlet. In the paper, as opposed to the previous studies, we discuss the capabilities of OPPEC technique for preparative separation of substances characterized by the same electrophoretic mobility. According to the proposed solution, the separation system can be periodically fed with the sample solution and separated components can be collected alternately at its outlet. The advantages of this new approach over the column chromatography with regard to the separation of complex mixtures have been signaled. [ABSTRACT FROM AUTHOR]

An online exoglycosidase digestion was combined with a plug-plug kinetic mode of capillary electrophoresis (CE) for the analysis of glycoprotein-derived oligosaccharides. An exoglycosidase solution and a solution of glycoprotein glycans derivatized with 8-aminopyrene-1,3,6-trisulfonic acid (APTS) were introduced to a neutrally coated capillary previously filled with electrophoresis buffer solution containing 0.5 w/v% hydroxypropylcellulose. After immersion of both ends of the capillary in the buffer solutions, a negative voltage was applied for analysis. An APTS group of an oligosaccharide derivative has triply negative charges, which forced saccharide derivatives to anode with fast mobility and pass through the enzyme plug, which are detected at the anodic end. If the terminal monosaccharides of APTS-labeled oligosaccharides are released by the action of an exoglycosidase, the migration times of the oligosaccharides shift to those of digested oligosaccharides. We examined β-galactosidase, α-mannosidase, β- N -acetylhexosaminidase, α-neuraminidase, and α-fucosidase, and found only β-galactosidase and α-neuraminidase showed good reactivity toward APTS-labeled oligosaccharides; the reaction was completed by injecting a 3.6 cm long plug of 200 and 50 mU/mL concentration of exoglycosidases. In contrast, other exoglycosidases could not react with APTS labeled oligosaccharides at a concentration up to 5 U/mL. The β- N -acetylhexosaminidase reaction was successively followed by the electrophoretic mobility of APTS oligosaccharides and stopped for 10 min when saccharide derivatives were achieved in the enzyme plug. The reaction of α-fucosidase and α-mannosidase was completed by decreasing the electrophoretic voltage to −2 kV when the APTS oligosaccharides were passing through an exoglycosidase plug. We established the CE conditions for all of the glycosidic linkage analysis of glycoprotein glycans. [ABSTRACT FROM AUTHOR]

An integrated, miniaturized and fully automated system was developed for the analysis (preconcentration/purification, separation and detection) of cis-diol containing molecules in complex matrices. This innovative in-line coupling system was achieved via the in-situ and localized synthesis of a short segment of silica-based monolith at the inlet of a 75-μm inner diameter fused silica capillary. The monolithic segment was locally functionalized with an acrylamide derivative of phenylboronic acid by free radical photopolymerization within 10 min of irradiation time. Efficiency of the photopolymerization reaction was followed by frontal affinity chromatography of 1,2-dihydroxybenzene (catechol) as cis-diol model solute. An active-site amount of 0.43 nmol cm −1 (9.8 nmol μL −1 ) of phenylboronic acid moieties was obtained, with a K d value of about 290 μM close to reported value for the phenyl boronate-catechol complex. The optimal conditions of use of the miniaturized boronate affinity monolithic column (μBAMC) were determined and adapted to the in-line coupling with capillary electrophoresis. Catechol was specifically preconcentrated in a pH 8.5 phosphate buffer/MeOH (80/20, v/v) mixture. A volume up to 20 times the monolith volume can be percolated with a quantitative recovery yield. Three catecholamines were purified, preconcentrated and in-line separated. Elution from the μBAMC was performed with a small plug of acidic solution, allowing field amplified sample stacking of solutes within the plug before their in-line electrophoretic separation at pH 8.75. This unique in-line coupling was successfully used for the fully automated analysis of catecholamines neurotransmitters in urine samples, highlighting the purification efficiency of the μBAMC and the potential of such a fully integrated approach. In addition to the low sample volume required (less than 2 μL), the limits of detection (LOD) accomplished with this coupling were estimated at 9.0, 9.5 and 4.8 ng mL −1 for dopamine, adrenaline and noradrenaline respectively, which improves the LOD of theses solutes compared to other CE methods. [ABSTRACT FROM AUTHOR]

The presence of inorganic anions in a sample interferes with mass spectrometric (MS) analysis. Here, a simple method to remove these ions from a liquid sample in one-step is described. The inorganic anions present in a 50 μL sample were extracted into a low pH solution inside a 200 μm i.d. × 33 cm long capillary by the use of an electric field. The selective removal of unwanted anions and retention of target analytes was accomplished by control of the apparent electrophoretic velocities of anions and analytes at a boundary that separated the sample and extraction solution. No physical barrier (e.g., membrane) was required and with the boundary situated at the tip of the capillary, efficient removal of inorganic anions (e.g., >80% removal) and good recovery of target analytes (e.g., >80% recovery) were achieved. The time required for removal of the inorganic anions was found to depend on their initial concentrations. The removal process was investigated using different concentrations of bromide and nitrate (as potassium salts) and negatively chargeable drugs as target analytes. This micro-sample clean-up technique used no organic solvents and little consumables and was studied to the determination of 0.6 μg/L arsenic and 8.3 μg/L vanadium in 500 mg/L sodium chloride using inductively coupled plasma MS and 50 μM angiotensin I in 1000 mg/L sodium chloride using electrospray ionisation MS. Micro-sample clean-up was performed for 45 min at 3 kV in both demonstrations. The calculated recoveries for the metals at trace levels were 110–130%, and for the peptide was 103.8%. [ABSTRACT FROM AUTHOR]

A portable microchip electrophoresis (MCE) coupled with on-chip contactless conductivity detection (C 4 D) system was evaluated for the determination of vancomycin in human plasma. In order to enhance the detection sensitivity, a new online multi-stacking preconcentration technique based on field-enhanced sample injection (FESI) and micelle-to-solvent stacking (MSS) was developed and implemented in MCE-C 4 D system equipped with a commercially available double T-junction glass chip. The cationic analytes from the two sample reservoirs were injected under FESI conditions and subsequently focused by MSS within the sample-loading channel. The proposed multi-stacking strategy was verified under a fluorescence microscope using Rhodamine 6G as the model analyte and a sensitivity enhancement factor (SEF) of up to 217 was achieved. The developed approach was subsequently implemented in the aqueous-based MCE, coupled to C 4 D in order to monitor the targeted antibiotic (in this case, vancomycin) present in human plasma samples. The multi-stacking and analysis time for vancomycin were 50 s and 250 s respectively, with SEF of approximately 83 when compared to typical gated injection. The detection limit of the method for vancomycin was 1.2 μg/mL, with intraday and interday repeatability RSDs of 2.6% and 4.3%, respectively. Recoveries in spiked human plasma were 99.0%–99.2%. [ABSTRACT FROM AUTHOR]

The concentration gradient detection method based on the Schlieren optics employed for electrophoresis analyses by extending the technology to a multi-channel system using a prototyped microfluidic chip (thinXXS Micro-technology, Germany). The results prove that coupling a chip-based microfluidic device with Schlieren detection is an appropriate approach to improve the electrophoretic separations. The effects of channel's geometry and dimension were investigated by conducting the experiments in channels with different cross sectional areas. Fast kinetic data acquisition of the charge-coupled device (CCD) camera facilitated recording of a time sequence of optical images, demonstrating the potential of the CCD camera as a powerful tool for studying dynamic processes such as diffusion. Diffusion coefficients of sample proteins were measured under static and dynamic conditions, where the static mode demonstrated more accurate results. Furthermore, the Fourier transformation was employed to improve the Schlieren images for quantitative analysis of the diffusion coefficient measurement. [ABSTRACT FROM AUTHOR]

• A critical overview of advances in microfluidic-based western blotting, highlighting advantages and disadvantages of each approach. • Particular focus on the development of now commercially available systems, including those for single cell analysis. • Includes recent developments in algorithms for automation, materials, projection electrophoresis and triBlots. • Future potential for use in point-of-care diagnostics is also discussed. Over the past two decades significant technical advancement in the field of western blotting has been made possible through the utilization of microfluidic technologies. In this review we provide a critical overview of these advancements, highlighting the advantages and disadvantages of each approach. Particular attention is paid to the development of now commercially available systems, including those for single cell analysis. This review also discusses more recent developments, including algorithms for automation and/or improved quantitation, the utilization of different materials/chemistries, use of projection electrophoresis, and the development of triBlots. Finally, the review includes commentary on future advances in the field based on current developments, and the potential of these systems for use as point-of-care devices in healthcare. [ABSTRACT FROM AUTHOR]

Bioactive species in cells can provide information about signal transduction, cell function, and the effects of disease treatment. In this article, a novel micro-biosensor was fabricated to detect glucose in individual human stomach cancer cells (MGC80-3 cells) with capillary electrophoresis (CE). We fabricated the micro-biosensors by immobilizing a single-walled carbon nanotube-glucose oxidase (GOx)-glutaraldehyde (GA) bio-composite at the palladium nanoparticle (PdNPs) modified Pt electrode. The linear concentration of glucose ranged from 2.0 μM to 1.0 mM, with a detection limit of 0.5 μM. Using this method, the mean amount of glucose in MGC80-3 cell extracts and in single cells was 20.0 fmol and 20 ± 6 fmol ( n = 10), respectively. The micro-biosensor exhibited high sensitivity, stability, and a long operating life, which are likely due to the biocompatible environment provided by BSA and GA, and the adsorption and faster electron transfer of SWNTs and PdNPs to GOx. [ABSTRACT FROM AUTHOR]

Ketamine is often used for anesthesia in veterinary medicine. One possible comedication is the sedative α 2 -agonist medetomidine. Advantages of that combination are the compensation of side effects of the two drugs and the anesthetic-sparing effect of medetomidine. In vitro studies showed that medetomidine has an inhibitive effect on the formation of norketamine. Norketamine is the first metabolite of ketamine and is also active. It is followed by others like 6-hydroxynorketamine and 5,6-dehydronorketamine (DHNK). In an in vivo pharmacokinetic study Beagle dogs under sevoflurane anesthesia (mean end-tidal concentration 3.0 ± 0.2%) or following medetomidine sedation (450 μg/m 2 ) received 4 mg/kg racemic ketamine or 2 mg/kg S-ketamine. Blood samples were collected between 0 and 900 min after drug injection. 50 μL aliquots of plasma were pretreated by liquid-liquid extraction prior to analysis of the reconstituted extracts with a robust enantioselective capillary electrophoresis assay using highly sulfated γ-cyclodextrin as chiral selector and electrokinetic sample injection of the analytes from the extract across a short buffer plug without chiral selector. Levels of S- and R-ketamine, S- and R-norketamine, (2S,6S)- and (2R,6R)-hydroxynorketamine and S- and R-DHNK were determined. Data were analyzed with compartmental pharmacokinetic models which included two compartments for the ketamine and norketamine enantiomers and a single compartment for the DHNK and 6-hydroxynorketamine stereoisomers. Medetomidine showed an effect on the formation and elimination of all metabolites. Stereoselectivities were detected for 6-hydroxynorketamine and DHNK, but not for ketamine and norketamine. [ABSTRACT FROM AUTHOR]

• In-depth information about the technology and the current state of the art. • Limitations, challenges, and remedies affecting the analytical performance of CE-SDS. • Critical review showing the progress and gaps with suggestions for improvement. • Where we stand and what we need to leverage the technology in various fields. The purpose of this review is to highlight noteworthy advancements in the field of capillary gel electrophoresis for the separation and analysis of proteins from the period of 2015-2021. This review will provide an overview of the historical perspective and principles of the technique, introduce the challenges and limitations commonly faced, and highlight the advancements made to overcome these issues and broaden our knowledge of the method. Finally, applications of capillary gel electrophoresis and future directions for the technique will be presented. [ABSTRACT FROM AUTHOR]

We reported sensitivity enhancement using multichannel parallel separation for microchip electrophoresis hyphenated with inductively coupled plasma mass spectrometry (MCE-ICP-MS) in this study. By using 2-20 array lanes for parallel separation, the sensitivity of the MCE-ICP-MS system was proportionally improved by 2-20 folds. No significantly adverse effect of parallel separation on column efficiency and resolution was observed. Rapid separation of Hg 2+ and methylmercuric (MeHg) ion within 36 s under an electric field of 800 V cm −1 was achieved in the 2-cm twenty-channels with a background electrolyte of 5 mmol L −1 borate buffer (pH 9.2). Detection limits of Hg 2+ and MeHg by the proposed system were decreased to 6.8–7.1 ng L −1 . Good agreement between determined values and certified values of a certified reference fish was obtained with recoveries ranged between 94–98%. All results prove its advantages including high sensitivity, high efficiency and low operation cost, which are beneficial to routine analysis of metal speciation in environmental, biological and food fields. [ABSTRACT FROM AUTHOR]

A new method for generating complex, dynamic pH profiles in an ampholyte-free separation channel is presented together with the theory behind its operation. The pH is modulated by an array of proton and hydroxide ion injectors placed along the separation channel. The ions generated in-situ by electrically driven water splitting across a bipolar membrane are injected to the channel in the presence of a longitudinal electric field, leading to the formation of a multi-step pH profile. Real-time control over the pH profile along the channel facilitates new dynamic separation strategies as well as steering and harvesting of focused molecules, which are both impossible with conventional separation methods. These freedoms are particularly attractive for Lab-on-a-Chip applications. The pH step-like profile alleviates one of the main hurdles of conventional isoelectric separation methods, namely, the slowing down of focused molecules as they approach their focusing spot. As a result, separation is completed within minutes for both peptides and proteins, even with low applied electric fields. We demonstrate protein and peptide separation within minutes, and resolution of ΔpI = 0.2. Novel separation strategies based on spatio-temporal pH control are demonstrated as well. [ABSTRACT FROM AUTHOR]

Insulator-based dielectrophoresis (iDEP) is a leading technique for the enrichment and manipulation of target bioparticles by exploiting physical and electrical properties of the particles and the suspending medium. Dielectrophoretic forces are produced by employing insulator posts that distort an otherwise uniform electric field. The optimal design for iDEP devices involves a careful balance between electrokinetics (EK) and dielectrophoresis (DEP) in the DEP-active area, where the design of the insulator posts is crucial for their performance. This contribution demonstrates the selection of a geometrical set of parameters that enhances particle capture and enrichment in an iDEP device. Numerical simulations, comprising an average trapping condition ( T C ) and the average lateral-to-longitudinal force ratio ( F R ) experienced by particles, were used to determine improved geometrical parameters ( e.g ., shape, length and width) and arrangement ( e.g ., lateral and longitudinal spacing) of the insulator posts. Experiments with polystyrene particles demonstrated the enhancement in particle enrichment, validating the employed key output parameters. The fabrication feasibility of the improved devices by a soft-lithographic process was also explored through numerical simulations and experiments. Optimal designs for this study were selected and their capture capacity was examined, demonstrating a decrease up to 84% in the electric potential necessary to generate a clear band of trapped particles. The findings from this study provide a systematic approach toward the design of high performance iDEP devices for their lab-on-a-chip integration. [ABSTRACT FROM AUTHOR]

The traditional recycling free-flow isoelectric focusing (RFFIEF) suffered from complex structure, tedious operations and poor extensibility as well as high cost. To address these issues, a novel reciprocating free-flow isoelectric focusing device (ReFFIEF) was developed for proteins or peptides pre-fractionation. In the new device, a reciprocating background flow was for the first time introduced into free flow electrophoresis (FFE) system. The gas cushion injector (GCI) used in the previous continuous free-flow electrophoresis (CFFE) was redesigned for the reciprocating background flow. With the GCI, the reciprocating background flow could be achieved between the GCI, separation chamber and transient self-balance collector (tSBC). In a run, process fluid flowed to and from, forming a stable reciprocating fluid flow in the separation chamber. A pH gradient was created within the separation chamber, and at the same time proteins were focused repeatedly when passing through the chamber under perpendicular electric field. The ReFFIEF procedure was optimized for fractionations of three model proteins, and the optimized method was further used for pre-fractionation of model human serum samples. As compared with the traditional RFFIEF devices developed about 25 years ago, the new ReFFIEF system showed several merits, such as simple design and structure, user-friendly operation and easy to extend as well as low cost. [ABSTRACT FROM AUTHOR]

Using a tee connector in a commercial capillary electrophoresis instrument, the effect of field amplified sample injection from both flowing and static sample volumes was investigated. It is shown that under identical conditions (40 min electrokinetic injection at 5 kV from a sample volume of 295 μL) the limit of detection using the continuous sample flow interface is 4 times lower than from a static vial. The relationship between different flow rates and injection voltages on the injected sample amount was also investigated using a 2D axisymmetric simulation (COMSOL 4.3b) and verified experimentally, confirming conditions under which there is near-quantitative injection of the sample target ions. Using electrokinetic injection at 30 kV and a flow rate of 558 nL/s the same enhancement from an even smaller volume of 184 μL could be achieved in 5.5 min than could be achieved from 295 μL and a 40 min injection. This sensitivity enhancement factor corresponded to four orders of magnitude improvement compared to a hydrodynamic injection. This is the first report showing that a continuous sample flow interface combined with stacking methods under conditions approaching quantitative injection from the entire sample volume has the potential to be more sensitive than a static system. [ABSTRACT FROM AUTHOR]

Capillary electrophoresis (CE) has been applied to determine the percentage of enantiomeric excess (ee%) of chiral compounds. In such assays, the quality of chiral selectors (CSs) plays vital roles in resolving the enantiomers for accurate determination of the ee%. Selecting an efficient CS is usually by trial and error, and is, if ever possible, time-consuming and costly. Here we propose a new approach by using the velocity gap mode of CE (VGCE) method, to simplify the method development process for ee% determination. With VGCE, it is still possible to measure ee% even when the CS has a weak resolving power. This is especially important at the extreme cases where one of the enantiomers is significantly higher than the other one. The key point of VGCE in this case is to fractionate the small part of the mixture containing both enantiomers from the major component of the enantiomer, which is already enantiopure. Baseline separations can be achieved between the two enantiomers for the small mixture due to less longitudinal dispersion, making it possible to determine the ee%. The feasibility of this VGCE approach was confirmed by the ee% measurements of amlodipine and ofloxacin, respectively. And the practical application of VGCE was tested by analyzing levamlodipine besylate tablet. [ABSTRACT FROM AUTHOR]

The present work analyzes the electrodynamic dispersion of sample streams in a free-flow zone electrophoresis (FFZE) chamber resulting due to partial or complete blockage of electroosmotic flow (EOF) across the channel width by the sidewalls of the conduit. This blockage of EOF has been assumed to generate a pressure-driven backflow in the transverse direction for maintaining flow balance in the system. A parallel-plate based FFZE device with the analyte stream located far away from the channel side regions has been considered to simplify the current analysis. Applying a method-of-moments formulation, an analytic expression was derived for the variance of the sample zone at steady state as a function of its position in the separation chamber under these conditions. It has been shown that the increase in stream broadening due to the electrodynamic dispersion phenomenon is additive to the contributions from molecular diffusion and sample injection, and simply modifies the coefficient for the hydrodynamic dispersion term for a fixed lateral migration distance of the sample stream. Moreover, this dispersion mechanism can dominate the overall spatial variance of analyte zones when a significant fraction of the EOF is blocked by the channel sidewalls. The analysis also shows that analyte streams do not undergo any hydrodynamic broadening due to unwanted pressure-driven cross-flows in an FFZE chamber in the absence of a transverse electric field. The noted results have been validated using Monte Carlo simulations which further demonstrate that while the sample concentration profile at the channel outlet approaches a Gaussian distribution only in FFZE chambers substantially longer than the product of the axial pressure-driven velocity and the characteristic diffusion time in the system, the spatial variance of the exiting analyte stream is well described by the Taylor–Aris dispersion limit even in analysis ducts much shorter than this length scale. [ABSTRACT FROM AUTHOR]

Sample preparation by electrophoretic concentration, followed by analysis using sweeping-micellar electrokinetic chromatography, was studied as a green and simple analytical strategy for the trace analysis of cationic drugs in water samples. Electrophoretic concentration was conducted using 50 mmol/L ammonium acetate at pH 5 as acceptor electrolyte. Electrophoretic concentration was performed at 1.0 kV for 50 min and 0.5 kV and 15 min for purified and 10-fold diluted waste water samples, respectively. Sweeping-micellar electrokinetic chromatography was with 100 mmol/L sodium phosphate at pH 2, 100 mmol/L sodium dodecyl sulfate and 27.5%-v/v acetonitrile as separation electrolyte. The separation voltage was −20 kV, UV-detection was at 200 nm, and the acidified concentrate was injected for 36 s at 1 bar (or 72% of the total capillary length, 60 cm). Both purified water and 10-fold diluted waste water exhibited a linear range of two orders of concentration magnitude. The coefficient of determination, and intra- and interday repeatability were 0.991–0.997, 2.5–6.2, and 4.4–9.7%RSD ( n = 6), respectively, for purified water. The values were 0.991–0.997, 3.4–7.1, and 8.7–9.8%RSD ( n = 6), correspondingly, for 10-fold diluted waste water. The method detection limit was in the range from 0.04–0.09 to 1.20–6.97 ng/mL for purified and undiluted waste water, respectively. [ABSTRACT FROM AUTHOR]

Herein, a novel strategy was developed to separate and prepare target protein from complex sample by free-flow electrophoresis (FFE), which mainly based on the charge-to-mass ratio ( C / M ) analysis of proteins. The C / M values of three model proteins, namely Cytochrome C (Cyt C), myoglobin (Mb) and bovine serum albumin (BSA) were analyzed under different pH and the separation of these proteins was predicted by CLC Protein Workbench software. Series of experiments were performed to validate the proposed method. The obtained data showed high accordance with our prediction. In addition, the chamber buffer (CB) of FFE system was optimized to improve the resolution of separation. Meanwhile, in order to evaluate the analytical performance of the proposed method, Cyt C was extracted from swine heart and further separated by FFE based on C / M analysis. Results showed that Cyt C was completely separated from the crude sample and a purity of 96.9% was achieved. The activity of prepared Cyt C was 98.3%, which indicate that the proposed method is promising in a wide variety of research areas where the native properties of proteins should be maintained for downstream analysis. [ABSTRACT FROM AUTHOR]

Orthogonal pressurized planar electrochromatography (OPPEC) is the new separation technique, in which two simultaneous and orthogonal processes of electrochromatography/electrophoresis and chromatography proceed under external pressure. It means in the OPPEC separation system a mobile phase solution hydrodynamically flows against adsorbent layer of the chromatographic plate and electric field is orthogonally applied to it. This technique can be applied to analytical and preparative separations. In the paper we report influence of some operating variables on continuous preparative OPPEC separation of test dyes in system with HPTLC RP-18W plates from Merck and methanol–buffer mobile phase. The following operation variables are discussed: external pressure exerted on the adsorbent layer, mobile phase flow velocity, and the ratio of flow velocities of the mobile phase to the sample solution, voltage applied to electrodes, modifier concentration in the mobile phase, concentration and pH of buffer. [ABSTRACT FROM AUTHOR]

This paper reports the development of a sub-minute separation method by capillary zone electrophoresis for the determination of aspartame, cyclamate, acesulfame-K and saccharin in food products and pharmaceutical samples. Separations were performed in a fused uncoated silica capillary with UV detection at 220 nm. Samples and standards were injected hydrodynamically using the short-end injection procedure. The electrophoretic system was operated under constant voltage of −30 kV. The background electrolyte was composed of 45 mmol L −1 2-amino-2-(hydroxymethyl)-1,3-propanediol and 15 mmol L −1 benzoic acid at pH 8.4. The separation time for all analytes was less than 1 min. Evaluation of analytical parameters of the method showed good linearity ( r 2 > 0.9972), limit of detection of 3.3–6.4 mg L −1 , intermediate precision better than 9.75% (peak area of sample) and recovery in the range of 91–117%. [ABSTRACT FROM AUTHOR]

Dual-opposite-injection capillary electrophoresis (DOI-CE) is a separation technique that utilizes both ends of the capillary for sample introduction. Depending on the individual electrophoretic mobilities of the analytes of interest and the migration distance that each analyte travels to the detection window, the elution order of analytes in a DOI-CE separation can vary widely. One consequence of a variable elution order is that co-detection of oppositely charged analytes becomes possible under certain experimental conditions. While several approaches currently exist to avoid co-detection, they are often time consuming and inefficient. This paper describes a systematic approach to easily avoid co-detection by analyzing the net mobilities of the analytes of interest to aid in choosing appropriate capillary lengths for a particular separation. Simulated electropherograms that highlight various aspects of this new approach are shown. An electropherogram from the literature is replicated and the derived relationship is applied to show the potential advantages of this new approach. [ABSTRACT FROM AUTHOR]

A method for separating water-insoluble and neutral synthetic polymers using non-aqueous capillary zone electrophoresis (NACZE) was developed. The non-aqueous solvent system comprising a mixture of tetrahydrofuran, acetonitrile, and ethanol containing cetyltrimethylammonium chloride was used for solubilizing and conferring positive charges to the polymers. A mixture of polystyrene (PS, M n = 6500) and polybutadiene (PBD, M n = 5900) was successfully separated by the NACZE method using cationic surfactants. Evaluation of the effect of the molecular weight of the polymers on the electrophoretic behavior demonstrated that PSs with different molecular weights ( M n = 6500, 10,200, 19,600, 200,000) were co-eluted as a single peak. That is, the apparent electrophoretic mobility of the PSs was independent of the molecular weight. In contrast, evaluation of PBD and polycarbonate (PC) demonstrated that the solubility of polymers in the medium affected the apparent electrophoretic mobility of the polymers, where low solubility resulted in reduced apparent electrophoretic mobility. Using the proposed method, poly(styrene- co -methylmethacrylate)s with different compositions were successfully separated. [ABSTRACT FROM AUTHOR]

The model of electromigration of a multivalent weak acidic/basic/amphoteric analyte that undergoes complexation with a mixture of selectors is introduced. The model provides an extension of the series of models starting with the single-selector model without dissociation by Wren and Rowe in 1992, continuing with the monovalent weak analyte/single-selector model by Rawjee, Williams and Vigh in 1993 and that by Lelièvre in 1994, and ending with the multi-selector overall model without dissociation developed by our group in 2008. The new multivalent analyte multi-selector model shows that the effective mobility of the analyte obeys the original Wren and Row's formula. The overall complexation constant, mobility of the free analyte and mobility of complex can be measured and used in a standard way. The mathematical expressions for the overall parameters are provided. We further demonstrate mathematically that the pH dependent parameters for weak analytes can be simply used as an input into the multi-selector overall model and, in reverse, the multi-selector overall parameters can serve as an input into the pH-dependent models for the weak analytes. These findings can greatly simplify the rationale method development in analytical electrophoresis, specifically enantioseparations. [ABSTRACT FROM AUTHOR]