Separation and characterization of sub-microm- and microm-sized particles by capillary zone electrophoresis

Capillary electrophoretic separation of nanoparticles

In the present work, CdSe nanocrystals (NCs) synthesized with a trioctylphosphine surface passivation layer were modified using amphiphilic molecules to form a surface bilayer capable of providing stable NCs aqueous solutions. Such modified nanocrystals were used as a test solute in order to analyze new electrophoretic phenomena, by applying a micellar plug as a separation tool for discriminating nanocrystals between micellar and micelle-free zones during electrophoresis. The distribution of NCs between both zones depended on the affinity of nanocrystals towards the micellar zone, and this relies on the kind of surface ligands attached to the NCs, as well as electrophoretic conditions applied. In this case, the NCs that migrated within a micellar zone can be focused using a preconcentration mechanism. By modifying electrophoretic conditions, NCs were forced to migrate outside the micellar zone in the form of a typical CZE peak. In this situation, a two-order difference in separation efficiencies, in terms of theoretical plates, was observed between focused NCs (N ~ 10(7)) and a typical CZE peak for NCs (N ~ 10(5)). By applying the amino-functionalized NCs the preconcentration of NCs, using a micellar plug, was examined, with the conclusion that preconcentration efficiency, in terms of the enhancement factor for peak height (SEF(height)) can be, at least 20. The distribution effect was applied to separate CdSe/ZnS NCs encapsulated in silica, as well as surface-modified with DNA, which allows the estimation of the yield of conjugation of biologically active molecules to a particle surface.

Multistage-multiorifice flow fractionation (MS-MOFF): continuous size-based separation of microspheres using multiple series of contraction/expansion microchannels

Previously we introduced a novel hydrodynamic method using a multi-orifice microchannel for size-based particle separation, which is called a multi-orifice flow fractionation (MOFF). The MOFF has several advantages such as continuous, non-intrusive, and minimal power consumption. However, it has a limitation that the recovery yield is relatively low. Although the recovery may be increased by adjusting parameters such as the Reynolds number and central collecting region, poor purity inevitably followed. We newly designed and fabricated a microfluidic channel for multi-stage multi-orifice flow fractionation (MS-MOFF), which is made by combining three multi-orifice segments, and consists of 3 inlets, 3 filters, 3 multi-orifice segments and 5 outlets. The structure and dimensions of the MS-MOFF were determined by the hydrodynamic principles to have constant Reynolds numbers at each multi-orifice segment. Polystyrene microspheres of two different sizes (7 μm and 15 μm) were tested. With this device, we made an attempt to improve recovery and minimize loss of purity by collecting and re-separating non-selected particles of the first separation. The final recovery successfully increased from 73.2% to 88.7% while the final purity slightly decreased from 91.4% to 89.1% (for 15 μm). These values were never achievable with the single-stage MOFF (SS-MOFF) having only one multi-orifice segment in our previous work. The MS-MOFF channel will be useful for clinical applications, such as separation of circulating tumor cells (CTC) or rare cells from human blood samples.

Study of single particle charge and Brownian motions with surface plasmon resonance

We demonstrated a method to accurately measure the zeta potentials and surface charges of individual particles by surface plasmon resonance microscopy (SPRM). The principle is based on the sensitive dependence of surface plasmons in a metal surface on the distance between a particle and the surface. By applying a periodic (ac) electric field to the metal surface, the charged particle oscillates, which is measured with SPRM, from which the zeta potential and the surface charge of the particle can be determined. The ac method reduces the electro-osmotic effect and noises induced by Brownian motions and allows for the rapid determination of the zeta potentials of individual particles.

Capillary electrophoretic separation and characterizations of CdSe quantum dots

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.

Fast determination of mitochondria electrophoretic mobility using micro free-flow electrophoresis

Fast, continuous separation of mitochondria from rat myoblasts using micro free-flow electrophoresis (muFFE) with online laser-induced fluorescence detection (LIF) is reported. Mitochondrial electrophoretic profiles were acquired in less than 30 s. In comparison to macroscale FFE instruments, muFFE devices consumed approximately 100-fold less sample, used 10-fold less buffer, and required a 15-fold lower electric field. Mitochondrial electrophoretic mobility distributions measured using muFFE were compared to those measured with a capillary electrophoresis instrument with laser-induced fluorescence detection (CE-LIF). There was high similarity between the two distributions with CE-LIF distribution being offset by 1.8 x 10(-4) cm(2) V(-1) s(-1) with respect to the microFFE distribution. We hypothesize that this offset results from the differences in electric field strength used in the techniques. In comparison to CE-LIF, analysis of mitochondria using muFFE greatly decreased separation time and required less separation voltage, while maintaining low sample (125 nL) and buffer (250 microL) volumes. These features together with the potential for collecting separated organelle fractions for further characterization make microFFE a very attractive tool for the high-throughput analysis of organelle subpopulations as well as investigating the fundamentals of the electrophoretic mobility of biological particles.

Characterization of copolymer latexes by capillary electrophoresis

Latexes are widely used for industrial applications, including decorative paints, binders for the papermaking industry, and drilling fluids for oil-field applications. In this work, the interest of capillary zone electrophoresis (CE) for the characterization of hydrophobic block copolymer latexes obtained by the conventional emulsion polymerization technique consisting of a core of polystyrene (PS) surrounded by a layer of poly(ethyl acrylate) (PEA) has been investigated. The PEA part of the copolymer can be partially hydrolyzed in poly(acrylic acid) (PAA) leading to PS-PEA-AA water-soluble amphiphilic copolymer having high viscosifying properties. The main purpose of this work was to evaluate the potential of CE for the characterization of the latexes at the different stages of the synthesis (PS core, PS-PEA diblock latex, and hydrolyzed PS-PEA-AA gel). The main analytical issues were to state (i) if there was free PS or PEA homopolymer latexes in the PS-PEA latex sample and (ii) if there was free PS, PEA, PS-PEA latexes, or free PAA chains in the PS-PEA-AA gel. Within this scope, this work describes the optimization of the selectivity of the separation between the different species (PS, PEA particles in the not hydrolyzed diblock latex and PS, PEA, PS-PEA particles as well as the polymer PAA chains in the PS-PEA-AA diblock gel sample obtained by latter latex hydrolysis). For that purpose, several experimental parameters were investigated such as pH and ionic strength of the background electrolyte (BGE) or the concentration of neutral surfactant added in the BGE. A challenging issue was to overcome the high viscosity of the PS-PEA-AA gel. This was resolved by the addition of 10 mM neutral surfactant in the gel sample and in the BGE. Finally, it is demonstrated that, within the detection limits, CE is a suitable analytical tool for controlling and monitoring the syntheses of these latexes and for intrinsically characterizing the distribution in charge density of the final PS-PEA-AA gel at different hydrolysis rates.

Evaluation of peak overlap in migration-time distributions determined by organelle capillary electrophoresis: Type-II error analogy based on statistical-overlap theory

Organelles commonly are separated by capillary electrophoresis (CE) with laser-induced-fluorescence detection. Usually, it is assumed that peaks observed in the CE originate from single organelles, with negligible occurrence of peak overlap. Under this assumption, migration-time and mobility distributions are obtained by partitioning the CE into different regions and counting the number of observed peaks in each region. In this paper, criteria based on statistical-overlap theory (SOT) are developed to test the assumption of negligible peak overlap and to predict conditions for its validity. For regions of the CE having constant peak density, the numbers of peaks (i.e., intensity profiles of single organelles) and observed peaks (i.e., maxima) are modeled by probability distributions. For minor peak overlap, the distributions partially merge, and their mergence is described by an analogy to the Type-II error of hypothesis testing. Criteria are developed for the amount of peak overlap, at which the number of observed peaks has an 85% or 90% probability of lying within the 95% confidence interval of the number of peaks of single organelles. For this or smaller amounts of peak overlap, the number of observed peaks is a good approximation to the number of peaks. A simple procedure is developed for evaluating peak overlap, requiring determination of only the peak standard deviation, the duration of the region occupied by peaks, and the number of observed peaks in the region. The procedure can be applied independently to each region of the partitioned CE. The procedure is applied to a mitochondrial CE.

Charge-based particle separation in microfluidic devices using combined hydrodynamic and electrokinetic effects

A new microfluidic approach for charge-based particle separation using combined hydrodynamic and electrokinetic effects is presented. A recirculating flow pattern is employed, generated through application of bi-directional flow in a narrow glass microchannel incorporating diverging or converging segments at both ends. The bi-directional flow in turn is a result of opposing pressure-driven flow and electro-osmotic flow in the device. Trapping and preconcentration of charged particles is observed in the recirculating flow, under conditions where the average net velocity of the particles themselves approaches zero. This phenomenon is termed flow-induced electrokinetic trapping (FIET). Importantly, the electrophoretic mobility (zeta potential) of the particles determines the flow conditions required for trapping. In this paper, we exploit FIET for the first time to perform particle separations. Using a non-uniform channel, one type of particle can be trapped according to its zeta-potential, while particles with higher or lower zeta-potentials are flushed away with the pressure-driven or electro-osmotic components, respectively, of the flow. This was demonstrated using simple mixtures of two polystyrene bead types having approximately the same size (3 microm) but different zeta potentials (differences were in the order of 25 to 40 mV). To gain more insight into the separation mechanism, particle separations in straight, 3 cm-long microchannels with uniform cross-section were also studied under conditions of bi-directional flow without trapping. A thorough theoretical analysis confirmed that trapping occurs when electrokinetic and pressure-driven particle velocities are equal and opposite throughout the diverging segment. This makes it possible to predict the pressure and electric field conditions required to separate particles having defined zeta potentials.

Capillary electrophoresis for the characterization of quantum dots after non-selective or selective bioconjugation with antibodies for immunoassay

Capillary electrophoresis coupled with laser-induced fluorescence was used for the characterization of quantum dots and their conjugates to biological molecules. The CE-LIF was laboratory-built and capable of injection (hydrodynamic and electrokinetic) from sample volumes as low as 4 μL via the use of a modified micro-fluidic chip platform. Commercially available quantum dots were bioconjugated to proteins and immunoglobulins through the use of established techniques (non-selective and selective). Non-selective techniques involved the use of EDCHCl/sulfo-NHS for the conjugation of BSA and myoglobin to carboxylic acid-functionalized quantum dots. Selective techniques involved 1) the use of heterobifunctional crosslinker, sulfo-SMCC, for the conjugation of partially reduced IgG to amine-functionalized quantum dots, and 2) the conjugation of periodate-oxidized IgGs to hydrazide-functionalized quantum dots. The migration times of these conjugates were determined in comparison to their non-conjugated QD relatives based upon their charge-to-size ratio values. The performance of capillary electrophoresis in characterizing immunoconjugates of quantum dot-labeled IgGs was also evaluated. Together, both QDs and CE-LIF can be applied as a sensitive technique for the detection of biological molecules. This work will contribute to the advancements in applying nanotechnology for molecular diagnosis in medical field.

Characterization of quantum dots using capillary zone electrophoresis

Commercially available quantum dots (QDs) were characterized using CE. The CE instruments were laboratory-built, each being capable of both electrokinetic and hydrodynamic injection. Modes of detection include UV absorption and LIF. The CE-LIF system was further modified to handle microliter sample volumes during injection. Sodium phosphate (5-25 mM, pH 7.5-11) was found to be a good buffer electrolyte. Sodium mercaptoproprionate CdTe/CdS (ADS620) QDs and carboxylic acid CdSe/ZnS (T2-Evitag) QDs yielded high separation efficiencies of N = 1.5x10(6) plates at t(M) = 10 min and N = 1.0x10(5) plates at t(M) = 3.8 min, respectively. Apparently the EDC/sulfo-NHS bioconjugation chemistry worked well with the neutral T2-Evitag QDs, but not so well with the negatively charged ADS620 QDs. This preliminary knowledge will serve as a basis for new CE immunoassay studies of QD-biomolecule conjugates and their immunocomplexes with target analytes.

On-line enhancement and separation of nanoparticles using capillary electrophoresis

We describe a rapid, simple, and highly efficient capillary electrophoresis (CE)-based method for the analysis of nanoparticles (NPs). In this study, we used the reversed electrode polarity stacking mode (REPSM) of CE to assess the feasibility of enhancing the detection of Au NPs and Au/Ag NPs, optimizing parameters such as the length of time for which the REPSM was applied, the concentrations of the buffer and the sodium dodecylsulfate (SDS) surfactant, and the pH. Under the optimized on-line enhancement conditions [buffer: SDS (40 mM) and 3-cyclohexylamino-1-propanesulfonic acid (CAPS; 10 mM) at pH 10.0; applied voltage: 20 kV; REPSM applied for 24s], the detection limits of the Au NPs and Au/Ag NPs increased by ca. 30- and 140-fold, respectively. In addition, when the NPs were subjected to on-line enhancement and separation by CE using diode array detection (DAD), this approach allowed chemical characterization of the NP species. Our results suggest that such CE analyses will be useful for accelerating the rates of fabrication and characterization of future nanomaterials.

CE analysis of the acidic organelles of a single cell

The properties of organelles within a cell have been shown to be highly heterogeneous. Until now, it has been unclear just how much of this heterogeneity is endemic to the organelle subpopulations themselves and how much is actually due to stochastic cellular noise. An attractive approach for investigating the origins of heterogeneity among the organelles of a single cell is CE with LIF detection (CE-LIF). As a proof of principle, in this report we optimize and use a single cell CE-LIF method to investigate the properties of endocytic (acidic) organelles. Our results show that the properties of individual acidic organelles containing Alexa Fluor 488 Dextran suggest that there are two groups of CCRF-CEM cells: a group with a high dextran content per cell, and a group with a low dextran content per cell. Furthermore, the individual organelle measurements of the single cells allow us to compare in each group the distributions of doxorubicin content per acidic organelle and electrophoretic mobilities of these organelles.

Evaluation of individual particle capillary electrophoresis experiments via quantile analysis

The number of particles in a sample heavily influences the shape of a distribution corresponding to the individual particle measurements. Selecting an adequate number of particles that prevents biases due to sample size is particularly difficult for complex biological systems in which statistical distributions are not normal. Quantile analysis is a powerful statistical technique that can rapidly compare differences between multiple distributions of individual particles. This report utilizes quantile analysis to show that the number of events detected affects the mobility distributions for rat liver and mouse liver mitochondria, sample individual particles, when analyzed via capillary electrophoresis with laser-induced fluorescence. When the mitochondrial sample is small (e.g. <78), there are not enough events to obtain statistically relevant mobility data. Adsorption to the capillary surface also significantly affects the mobility distribution at a small number of events in uncoated and dynamically coated capillaries. These adsorption effects can be overcome when the mitochondrial load on the capillary is sufficiently large (i.e. >609 and >1426 events for mouse liver on uncoated capillaries and rat liver on dynamically coated capillaries, respectively). It is anticipated that quantile analysis can be used to study other distributions of individual particles, such as nanoparticles, organelles, and biomolecules, and that distributions of these particles will also be dependent on sample size.

Analysis of subcellular sized particles

Flow cytometry (FCM) and more recently capillary electrophoresis with post-column laser-induced fluorescence detection (CE-LIF) have both been used for subcellular particle analysis but their analytical performance has not been compared. In this work, we compare a commercial FCM with an in-house built CE-LIF instrument using fluorescently labeled microspheres and isolated mitochondria. As evidenced by the relative standard deviation (RSD) of the individual fluorescence intensities, FCM is two-fold better than CE-LIF for microspheres with > or =1.5 x 10(6) molecules of equivalent soluble fluorescein (MESF). However, FCM has a comparatively low signal-to-noise ratio (S/N) and high RSD for microspheres with <1.5 x 10(6) MESF. CE-LIF, on the other hand, produces S/N ratios that are >25 times higher than FCM for all the microspheres tested and a lower RSD for microspheres with <1.5 x 10(6) MESF. When 10-N-nonyl acridine orange (NAO)-labeled mitochondria are analyzed, the S/N ratios of both techniques are similar. This appears to result from photobleaching of NAO-labeled mitochondria as they are detected by the LIF detector of the CE-LIF instrument. Both techniques have a niche in subcellular analysis; FCM has the advantage of collecting data for thousands of particles quickly, whereas CE-LIF consumes less than a nanoliter of sample and provides the electrophoretic mobility for individual particles.

Physico-chemical characterization and transfection efficacy of cationic liposomes containing the pEGFP plasmid

Cationic liposomes-DNA complexes (lipoplexes) are largely used in gene delivery. Deciphering specific chemical and physical properties of lipoplexes is a necessary step to unravel the mechanisms underlying transfection and to improve transfection efficacy in each experimental model. In the present paper we investigated the physico-chemical features of lipoplexes containing a plasmid encoding for the GFP protein, in order to correlate these results with transfection efficacy. Cationic unilamellar vesicles (mean diameter 100 nm) were prepared, from the cationic DC-Chol lipid and the zwitterionic phospholipid DOPE. The two components of the liposome bilayer were used at molar ratio close to unity. ESR spectra were recorded and zeta potential zeta was measured on liposomes complexed with the plasmid. One of the main points of interest in this paper resided in the fact that both kinds of measurements were carried out in the same conditions (i.e. lipid concentration, medium composition, and pH) employed for cell transfection experiments. Transfection was performed on CHO cells; the percentage of fluorescent cells was evaluated and compared with the above physico-chemical features. It emerged that the composition and pH of the medium, the lipoplex/cell ratio, as well as the amount of lipoplex added to the cell culture were critical parameters for transfection efficacy. Finally, lipoplex surface charge played a fundamental role to achieve a high transfection level.

Separation of cationic polymer particles and characterization of avidin-immobilized particles by capillary electrophoresis

Cationic polymer microparticles have received much attention especially in the field of biotechnology, such that their analysis and separation have become important. So far, the separation of cationic polymer particles with different size using CE has not been achieved and the cationic particles migrated as if they are negatively charged, probably due to electrostatic interaction between capillary wall and cationic polymer particles. In this paper, the separation of cationic polymer microparticles by CE was investigated in detail. The separation of cationic particles with different size was achieved in CE by taking into account the interaction between sample particles and the inner surface of capillaries. By employing a poly(vinyl alcohol)-coated capillary, a better size separation of amine-modified latex particles was obtained compared to a Polybrene-coated capillary. It was elucidated that the composition, concentration, and pH of the background solution were also important factors in the separation of colloidal particles to avoid the surface adsorption and the characteristic aggregation of polymer particles. Furthermore, the CE analysis was applied to the characterization of cationic protein-immobilized particles.

On-column labeling for capillary electrophoretic analysis of individual mitochondria directly sampled from tissue cross sections

This technical note reports on a new procedure to on-column-label organelles sampled from a tissue cross section into a fused silica capillary. These organelles are then analyzed by capillary electrophoresis with postcolumn laser-induced fluorescence detection. In this procedure, the fluorescent label does not come in contact with the tissue, which facilitates visualization of the sampled tissue cross section. In addition, on-column labeling allows for better control of the reaction time and fluorescent label concentrations. As a proof-of-principle, we show results of mitochondria from rat gastrocnemius muscle cross sections that were on-column-labeled with 10-N-nonyl acridine orange (NAO), a mitochondrion-specific probe, and compare them with results for NAO in-tissue labeling of the same tissue. The new organelle labeling procedure reported here may easily be extended to the analysis of individual organelles in other biological samples and may become a valuable tool in studies investigating the role of mitochondria in muscle aging and exercise physiology.

Diffusiophoresis and electrophoresis of a charged sphere parallel to one or two plane walls

The diffusiophoretic and electrophoretic motions of a dielectric spherical particle in an electrolyte solution located between two infinite parallel plane walls are studied theoretically. The imposed electrolyte concentration gradient or electric field is constant and parallel to the two plates, which may be either impermeable to the ions/charges or prescribed with the far-field concentration/potential distribution. The electrical double layer at the particle surface is assumed to be thin relative to the particle radius and to the particle-wall gap widths, but the polarization effect of the mobile ions in the diffuse layer is incorporated. The presence of the neighboring walls causes two basic effects on the particle velocity: first, the local electrolyte concentration gradient or electric field on the particle surface is enhanced or reduced by the walls, thereby speeding up or slowing down the particle; second, the walls increase the viscous retardation of the moving particle. To solve the conservative equations, the general solution is constructed from the fundamental solutions in both rectangular and spherical coordinates. The boundary conditions are enforced first at the plane walls by the Fourier transforms and then on the particle surface by a collocation technique. Numerical results for the diffusiophoretic and electrophoretic velocities of the particle relative to those of a particle under identical conditions in an unbounded solution are presented for various values of the relevant parameters including the relative separation distances between the particle and the two plates. For the special case of motions of a spherical particle parallel to a single plate and in the central plane of a slit, the collocation results agree well with the approximate analytical solutions obtained by using a method of reflections. The presence of the lateral walls can reduce or enhance the particle velocity, depending on the properties of the particle-solution system, the relative particle-wall separation distances, and the electrochemical boundary condition at the walls. In general, the boundary effects on diffusiophoresis and electrophoresis are quite significant and complicated, and they no longer vary monotonically with the separation distances for some situations.

Dynamic modification of microorganisms by pyrenebutanoate for fluorometric detection in capillary zone electrophoresis

Pyrenebutanoate, a fluorescent amphiphilic probe, is suggested here as a capillary zone electrophoresis (CZE) buffer additive for dynamic modification and analysis of microbial cells. Mixed cultures of microorganisms Escherichia coli, Candida albicans, Enterococcus faecalis and Staphylococcus epidermidis were concentrated, resolved by CZE and detected. Using UV excitation for on-column fluorometric detection, a detection sensitivity for the microorganisms on the order of from one to tens of injected cells was achieved.

Lipid vesicles in capillary electrophoretic techniques: characterization of structural properties and associated membrane-molecule interactions

This paper reviews the use of lipid vesicles as model membranes in capillary electrophoresis (CE). The history and utility of CE in the characterization of microparticles is summarized, focusing on the application of colloidal electromigration theories to lipid vesicles. For instance, CE experiments have been used to characterize the size, surface properties, enclosed volumes, and electrophoretic mobilities of lipid vesicles and of lipoprotein particles. Several techniques involving small molecules or macromolecules separated in the presence of lipid vesicles are discussed. Interactions between the analytes and the lipid vesicles - acting as a pseudostationary phase or coated stationary phase in electrokinetic chromatography (EKC) - can be used to obtain additional information on the characteristics of the vesicles and analytes, and to study the biophysical properties of membrane-molecule interactions in lipid vesicles and lipoproteins. Different methods of determining binding constants by EKC are reviewed, along with the relevant binding constant calculations and a discussion of the application and limitations of these techniques as they apply to lipid vesicle systems.

Influence of cetyltrimethylammonium bromide on phosphatidylcholine-coated capillaries

Large unilamellar vesicles of egg-phosphatidylcholine (eggPC), a naturally occurring phospholipid, were used in capillary electrophoresis (CE) for semi-permanent coating of fused silica capillaries. The stability of the phospholipid coating was tested at different cetyltrimethylammonium bromide (CTAB) concentrations with and without CaCl(2) present in the coating solution. The effect of physical factors influencing the coating stability (e.g. duration of the coating time, storage temperature of the coating solution) were also studied. Standing overnight in background electrolyte (BGE) solution did not alter the eggPC phospholipid coating noticeably. The performance of the coating was tested with a mixture of basic proteins (lysozyme, ribonuclease A and alpha-chymotrypsinogen A). Highest efficiencies (over 200,000 plates m(-1)) were achieved when the capillary was filled for 15 h with a liposome solution containing both CTAB and CaCl(2).

Electrophoretic aggregation of humic acid

Capillary electrophoresis (CE) has been used to characterize humic acid (HA) aggregation. It was found that when pumping HA solution through the capillary at a constant flow rate with no electric field, the number of spikes could be reduced by filtration of the solution. Applying high voltage (30 kV), the amount of spikes increased again. This is associated with the formation of new aggregates caused by electric field. Aggregation is influenced by the concentration of HA, applied voltage and presence of imidazole in the solution. It is supposed that this phenomenon is characteristic of all solutions that can form colloidal particles: in beta-cyclodextrin solution, similar spikes appear in a high-voltage electric field.

Separation and analysis of colloidal/nano-particles including microorganisms by capillary electrophoresis: a fundamental review

A review is presented on the CE analysis of colloidal/nano particles. Topics discussed include the CE separation of polymeric, inorganic, microbial (i.e. viruses, bacteria, fungi, and whole cells), and sub-cellular particles (i.e. mitochondria and nuclei). Several of the encountered difficulties in analysis are presented as well as the methods employed to overcome them.