Field-Flow Fractionation: Theory, Techniques, Applications and the Challenges

Increasing the Resolution of Field-Flow Fractionation with Increasing Crossflow Gradients

The resolution of flow field-flow fractionation (flow FFF) depends primarily on the crossflow rate and its change over time. In this work, we demonstrate a method for modulation of the crossflow rate during separation that increases the peak-to-peak resolution of the resulting fractograms. In classical FFF methods, the crossflow rate is either maintained constant or decreased during the separation of the different species. In this work, higher resolution between peaks was achieved by a novel gradient method in which the crossflow is increased briefly during separation to allow stronger retention of the later eluting peaks. We first outline the theoretical basis by which improved separation is achieved. We confirm our hypothesis by quantifying the impact of increasing crossflow on the resolution between a monoclonal antibody monomer and its high-molecular-weight aggregate. We then demonstrate that this method is applicable to two different FFF methods (AF4 and HF5) and various pharmaceutically relevant samples (monoclonal antibodies and adeno-associated viruses). Finally, we hypothesize that increasing the force perpendicular to the laminar flow as described here is broadly applicable to all FFF methods and improves the quality of FFF-based separations.

Incorporation of a Morphologically Controlled Ice Grain Boundary into a Microfluidic Device for Size-Selective Separation of Micro/Nanospheres

A frozen aqueous solution was integrated into a microfluidic device as a size-tunable separation field for the size-selective separation of micro/nanospheres. The width of the ice grain boundaries formed in frozen aqueous solutions could be altered by controlling the operating temperature. A freezing chamber was placed adjacent to the microfluidic channel. A sample-dispersing aqueous sucrose solution was injected into the chamber and frozen, allowing the freeze-concentrated solution (FCS) to run vertically to the microfluidic channel, where the eluting solution flows. The operating temperature can be used to control the physical interaction between the ice wall and micro/nanospheres, enabling size-selective migration. The eluted micro/nanospheres in the microchannel were passed through the eluting solution collected from the outlet. We achieved size-selective separation and collection of microspheres and nanospheres. We separated the exosomes and yeast cells to demonstrate their applicability in bioseparation. The present method is suitable not only for size-selective separation but also for evaluating the biological expression of extracellular vesicles under cryogenic conditions.

Offline Coupling of Asymmetrical Flow Field-Flow Fractionation and Capillary Electrophoresis for Separation of Extracellular Vesicles

Extracellular vesicles (EVs) play important roles in cell-to-cell communications and carry high potential as markers targeted in disease diagnosis, prognosis, and therapeutic development. The main obstacles to EV study are their high heterogeneity; low amounts present in samples; and physical similarity to the abundant, interfering matrix components. Multiple rounds of separation and purification are often needed prior to EV characterization and function assessment. Herein, we report the offline coupling of asymmetrical flow field-flow fractionation (AF4) and capillary electrophoresis (CE) for EV analysis. While AF4 provides gentle and fast EV separation by size, CE resolves EVs from contaminants with similar sizes but different surface charges. Employing Western Blotting, ELISA, and SEM, we confirmed that intact EVs were eluted within a stable time window under the optimal AF4 and CE conditions. We also proved that EVs could be resolved from free proteins and high-density lipoproteins by AF4 and be further separated from the low-density lipoproteins co-eluted in AF4. The effectiveness of the coupled AF4-CE system in EV analysis was demonstrated by monitoring the changes in EV secretion from cells and by direct injection of human serum and detection of serum EVs. We believe that coupling AF4 and CE can provide rapid EV quantification in biological samples with much reduced matrix interference and be valuable for the study of total EVs and EV subpopulations produced by cells or present in clinical samples.

Wide-Range Size Fractionation of Graphene Oxide by Flow Field-Flow Fractionation

Many interesting properties of 2D materials and their assembled structures are strongly dependent on the lateral size and size distribution of 2D materials. Accordingly, effective size separation of polydisperse 2D sheets is critical for desirable applications. Here, we introduce flow field-flow fractionation (FlFFF) for a wide-range size fractionation of graphene oxide (GO) up to 100 μm. Two different separation mechanisms are identified for FlFFF, including normal mode and steric/hyperlayer mode, to size fractionate wide size-distributed GOs while employing a crossflow field for either diffusion or size-controlled migration of GO. Obviously, the 2D GO sheet reveals size separation behavior distinctive from typical spherical particles arising from its innate planar geometry. We also investigate 2D sheet size-dependent mechanical and electrical properties of three different graphene fibers produced from size-fractionated GOs. This FlFFF-based size selection methodology can be used as a generic approach for effective wide-range size separation for 2D materials, including rGO, TMDs, and MXene.

Optimization of hyphenated asymmetric flow field-flow fractionation for the analysis of silver nanoparticles in aqueous solutions

The extensive use of silver nanoparticles (AgNPs) in consumer products, medicine, and industry leads to their release into the environment. Thus, a characterization of the concentration, size, fate, and toxicity of AgNPs under environmental conditions is required. In this study, we present the characterization and optimization of an asymmetric flow field-flow fractionation (AF4) system coupled with UV/Vis spectrophotometer and dynamic light scattering (DLS) detector as a powerful tool for the size separation and multi-parameter characterization of AgNPs in complex matrices. The hyphenated AF4-UV/Vis-DLS system was first characterized using individual injections of the different size fractions. We used electrostatically stabilized AgNPs of 20-, 50-, and 80-nm nominal diameters coated with lipoic acid. We investigated the effect of applied cross-flows, carrier solutions, focus times, and quantity of injected particles on the nature of the AF4 fractograms and on the integrity of the AgNPs. Best size separation of a 1:1 mixture of 20- and 80-nm AgNPs was achieved using cross-flows of 0.5 and 0.7 mL/min with 1 mM NaCl and 0.05% v/v Mucasol as carrier solutions. We also researched the behavior of AgNPs in natural waters using the hyphenated AF4-UV/Vis-DLS system, under determined optimal conditions. Schematic and photograph of the AF4 setup with numbered hardware devices. Dashed lines represent electrical connections; continuous lines represent fluidic connections. For a better overview, not all fluidic connections between pump/6-way valve (2) and the Eclipse AF4 device (3) are shown in the schematic. The fluorescence detector (FL (7)) was not used in the study presented herein.

Characterization of dextran particle size: How frit-inlet asymmetrical flow field-flow fractionation (FI-AF4) coupled online with dynamic light scattering (DLS) leads to enhanced size distribution

Accurate determinations of particle size and particle size distribution (PSD) are essential to achieve the clinical translation of medical nanoparticles (NPs). Herein, dextran-based NPs produced via a water-in-oil emulsification/crosslinking process and developed as nanomedicines were studied. NPs were first characterized using traditional batch-mode techniques as dynamic light scattering (DLS) and laser diffraction. In a second step, their analysis by frit-inlet asymmetrical flow field-flow fractionation (FI-AF4) was explored. The major parameters of the AF4 procedure, namely, crossflow, detector flow, crossflow decay programming and relaxation time were set up. The sizes of the particle fractions eluted under optimized conditions were measured using DLS as an online detector. We demonstrate that FI-AF4 is a powerful method to characterize dextran-NPs in the 200 nm -1 µm range. It provided a more realistic and comprehensive picture of PSD, revealing its heterogenous character and clearly showing the ratio of different populations in the sample, while batch-mode light scattering techniques only detected the biggest particle sizes.

Dealing with the complexity of conjugated and self-assembled polymer-nanostructures using field-flow fractionation

Broad diversity and heterogeneity are inherently showcased by both natural and synthetic macromolecular structures. The high application potential for such structures and their combinations calls for novel analytical approaches that allow for comprehensive characterization and a full understanding of their complex composition. This review gives an overview of recent advances in designing and fabricating bioconjugated and self-assembled polymer structures, and introduces adequate characterization protocols for sufficient elucidation of their specific molecular properties. Possible pitfalls in their analysis are demonstrated, and potential alternatives are discussed. The primary focus is on addressing the highlights, and future prospects of applying field-flow fractionation coupled and/or hyphenated to different detection methods as a powerful separation and analytical technique for bioconjugate and self-assembled nanostructures.

Isolation and Self-Association Studies of Beta-Lactoglobulin

The aim of this study was to investigate isolated β-lactoglobulin (β-LG) from the whey protein isolate (WPI) solution using the column chromatography with SP Sephadex. The physicochemical characterization (self-association, the pH stability in various salt solutions, the identification of oligomeric forms) of the protein obtained have been carried out. The electrophoretically pure β-LG fraction was obtained at pH 4.8. The fraction was characterized by the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/TOF MS) technique. The use of the HCCA matrix indicated the presence of oligomeric β-LG forms, while the SA and DHB matrices enabled the differentiation of A and B isoforms in the sample. The impact of sodium chloride, potassium chloride, ammonium sulfate, and sodium citrate in dispersion medium on β-LG electrophoretic stability in solution was also studied. Type of the dispersion medium led to the changes in the isoelectric point of protein. Sodium citrate stabilizes protein in comparison to ammonium sulfate. Additionally, the potential of capillary electrophoresis (CE) with UV detection using bare fused capillary to monitor β-LG oligomerization was discussed. Obtained CE data were further compared by the asymmetric flow field flow fractionation coupled with the multi-angle light scattering detector (AF4-MALS). It was shown that the β-LG is a monomer at pH 3.0, dimer at pH 7.0. At pH 5.0 (near the isoelectric point), oligomers with structures from dimeric to octameric are formed. However, the appearance of the oligomers equilibrium is dependent on the concentration of protein. The higher quantity of protein leads to the formation of the octamer. The far UV circular dichroism (CD) spectra carried out at pH 3.0, 5.0, and 7.0 confirmed that β-sheet conformation is dominant at pH 3.0, 5.0, while at pH 7.0, this conformation is approximately in the same quantity as α-helix and random structures.

Dielectrophoresis-field flow fractionation for separation of particles: A critical review

Dielectrophoresis-field flow fractionation (DEP-FFF) has emerged as an efficient in-vitro, non-invasive, and label-free mechanism to manipulate a variety of nano- and micro-scaled particles in a continuous-flow manner. The technique is mainly used to fractionate particles/cells based on differences in their sizes and/or dielectric properties by employing dielectrophoretic force as an external force field applied perpendicular to the flow direction. The dielectrophoretic force is the result of a spatially non-uniform electric field in the microchannel that can be generated either by exploiting microchannel geometry or using special arrangements of microelectrode arrays. Several two-dimensional (e.g., coplanar interdigitated, castellated) and three-dimensional (e.g., top-bottom, side-wall) microelectrode designs have been successfully utilized to perform fractionation of heterogeneous samples. Although originally introduced as a separation technique, DEP-FFF has attracted increasing interest in performing other important operations such as switching, focusing, dipping, and surface functionalization of target particles. Nonetheless, the technique still suffers from limitations such as low throughput and joule heating. By comparatively analyzing recent developments that address these shortcomings, this work is a step forward towards realizing the full potential of DEP-FFF as an ideal candidate for point-of-care (POC) devices with diverse applications in the fields of biomedical, chemical, and environmental engineering.

Starch and Glycogen Analyses: Methods and Techniques

For complex carbohydrates, such as glycogen and starch, various analytical methods and techniques exist allowing the detailed characterization of these storage carbohydrates. In this article, we give a brief overview of the most frequently used methods, techniques, and results. Furthermore, we give insights in the isolation, purification, and fragmentation of both starch and glycogen. An overview of the different structural levels of the glucans is given and the corresponding analytical techniques are discussed. Moreover, future perspectives of the analytical needs and the challenges of the currently developing scientific questions are included.

Characterization and differential retention of Q beta bacteriophage virus-like particles using cyclical electrical field-flow fractionation and asymmetrical flow field-flow fractionation

Virus-like particles (VLPs) are widely used in medicine, but can be difficult to characterize and isolate from aggregates. In this research, primarily cyclical electrical field-flow fractionation (CyElFFF) coupled with multi-angle light scattering (MALS), and dynamic light scattering (DLS) detectors, was used for the first time to perform size and electrical characterization of three different types of Q beta bacteriophage virus-like particles (VLPs): a blank Q beta bacteriophage which is denoted as VLP and two conjugated ones with different peptides. The CyElFFF results were verified with transmission electron microscopy (TEM). Asymmetrical flow field-flow fractionation (AF4) coupled with MALS was also applied using conditions similar to those used in the CyElFFF experiments, and the results of the two techniques were compared to each other. Using these techniques, the size and electrophoretic characteristics of the fractionated VLPs in CyElFFF were obtained. The results indicate that CyElFFF can be used to obtain a clear distribution of electrophoretic mobilities for each type of VLP. Accordingly, CyElFFF was able to differentially retain and isolate VLPs with high surface electric charge/electrophoretic mobility from the ones with low electric charge/electrophoretic mobility. Regarding the size characterization, the size distribution of the eluted VLPs was obtained using both techniques. CyElFFF was able to identify subpopulations that did not appear in the AF4 results by generating a shoulder peak, whereas AF4 produced a single peak. Different size characteristics of the VLPs appearing in the shoulder peak and the main peak indicate that CyElFFF was able to isolate aggregated VLPs from the monomers partially. Graphical abstract.

Cadmium-affected synthesis of exopolysaccharides by rhizosphere bacteria

AIM

Study is focused on the influence of cadmium addition to growth media on production yield, their size and molecular mass of exopolysaccharides (EPS) synthesized by three rhizosphere bacteria strains. Inhibition of bacterial growth by increasing concentrations of Cd²⁺ was also analysed.

METHODS AND RESULTS

The highest impact of Cd²⁺ was noticed on the growth of Arthrobacter sp. and Rhizobium metallidurans. Chryseobacterium sp. and Arthrobacter sp. produced significantly lower when compared to R. metallidurans amounts of EPS under the influence of Cd²⁺ . In all bacterial strains both size and molecular mass decreased after addition of Cd²⁺ to growth media. It causes a change in EPS conformation to more planar, which minimizes the volume of liquid in the interglobular space next to the bacterial wall. Results confirmed strong effect of Cd²⁺ on the structure and synthesis of bacterial EPS what can be a key factor in the interactions between rhizosphere bacteria and host plants in heavy metal polluted soils.

CONCLUSION

This work proves that due to the presence of cadmium ions, the size and conformation of EPS produced by selected bacterial strains is changed to minimize their impact on cell. We suggest that shifting in EPS conformation from bigger globular particles to the smaller planar ones could be one of the probable mechanisms of Cd resistance in metallotolerant bacteria, and finally explain increased efficiency of heavy metal phytoextraction by EPS-producing plant growth-promoting micro-organisms.

SIGNIFICANCE AND IMPACT OF THE STUDY

One of the most promising remediation technique for Cd-contaminated areas is the phytoremediation in which rhizosphere bacteria play an important role by protecting plants' roots from toxic condition thus enhancing efficiency of intake. EPS secretion by bacteria is one of the most common mechanisms to protect the cell from impact of unpleasant environmental conditions, for example, toxicity of heavy metals like Cd.

Impact of Ionic Strength of Carrier Liquid on Recovery in Flow Field-Flow Fractionation

Asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) are techniques widely used in analytical, industrial and biological analyses. The main problem in all AF4 and HF5 analyses is sample loss due to analyte–membrane interactions. In this work the impact of liquid carrier composition on latex nanoparticles (NPs) separation in water and two different concentrations of NH₄NO₃ was studied. In AF4, a constant trend of decreasing the size of 60 and 121.9 nm particles induced by the ionic strength of the carrier liquid has been observed. In contrast, an agglomeration effect of the biggest 356 nm particles was observed when increasing ionic strength, which induced a significant drop of recovery to 35%. H5F provides better resolution and intensified peaks of NPs, but careful optimisation of system parameters is mandatory to obtain good separation.

Thermophoretic migration of vesicles depends on mean temperature and head group chemistry

A number of colloidal systems, including polymers, proteins, micelles and hard spheres, have been studied in thermal gradients to observe and characterize their driven motion. Here we show experimentally the thermophoretic behaviour of unilamellar lipid vesicles, finding that mobility depends on the mean local temperature of the suspension and on the structure of the exposed polar lipid head groups. By tuning the temperature, vesicles can be directed towards hot or cold, forming a highly concentrated region. Binary mixtures of vesicles composed of different lipids can be segregated using thermophoresis, according to their head group. Our results demonstrate that thermophoresis enables robust and chemically specific directed motion of liposomes, which can be exploited in driven processes.

Thermal gradients are shown to provide a robust and chemically specific driving force to liposomes. Here the authors show controlled direction of migration of unilamellar lipid vesicles by varying the temperature in the suspension and the exposed polar lipid head groups.

Field-flow fractionation of nano- and microparticles in rotating coiled columns

Field-flow fractionation (FFF) is a very powerful and versatile set of liquid chromatography-like elution methods. However, conventional FFF separations occur in thin channels and the sample weight injected is usually less than 1 mg to avoid overloading. The fractionation in a rotating coiled column (RCC), which can be attributed to sedimentation FFF, enables the handling sample weight to be increased at least up to 1 g. An uneven distribution of particles in RCC was first observed by Y. Ito et al. in 1966. The work in this direction was continued by P.S. Fedotov et al. in 2000. Regularities of the behaviour of nano- and microparticles of different size and origin in RCCs with different design parameters were systematically studied taking as example silica particles, latex beads, quartz sand, clay minerals, and other samples. The basic principles of the new FFF method were established. The developed method was applied to the speciation analysis of polydisperse environmental samples, in particular, for the separation of soils into silt, clay and sand fractions. For the first time, nano- and submicron particles of street dust have been separated, weighted, characterized by electronic microscopy, and quantitatively analyzed by ICP-MS (after digestion). The elements that may be of anthropogenic origin (Zn, Cr, Ni, Cu, Cd, Sn, Pb) were found to concentrate mainly in <0.3 and 0.3-1 μm fractions. It has been shown that the concentrations of Cr, Ni, Zn in the finest fraction (<0.3 μm) of street dust can be one order of magnitude higher than the concentrations of elements in bulk sample. The fractionation in RCC was also used for the recovery of a nearly monodisperse fraction (4.5 μm) of a chromatographic sorbent based on polystyrene-divinylbenzene; impurities remaining from the synthesis and smaller particles (1-2 μm) being removed. Study on the fractionation of synthetic samples has demonstrated the applicability of the method to the preparative separation and purification of polydisperse materials.

Application of an asymmetric flow field flow fractionation multi-detector approach for metallic engineered nanoparticle characterization--prospects and limitations demonstrated on Au nanoparticles

In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system. For good separation performance, the A4F flow-, membrane-, and carrier conditions were optimized. To obtain reliable size information, the use of laser light scattering based detectors was evaluated, where an online dynamic light scattering (DLS) detector showed good results for the investigated Au-NP up to a size of 80 nm in hydrodynamic diameter. To adapt large sensitivity differences of the various detectors, as well as to guarantee long term stability and minimum contamination of the mass spectrometer a split-flow concept for coupling ICPMS was evaluated. To test for reliable quantification, the ICPMS signal response of ionic Au standards was compared to that of Au-NP. Using proper stabilization with surfactants, no difference for concentrations of 1-50 μg Au L(-1) in the size range from 5 to 80 nm for citrate stabilized dispersions was observed. However, studies using different A4F channel membranes showed unspecific particle-membrane interaction resulting in retention time shifts and unspecific loss of nanoparticles, depending on the Au-NP system as well as membrane batch and type. Thus, reliable quantification and discrimination of ionic and particular species was performed using ICPMS in combination with ultracentrifugation instead of direct quantification with the A4F multi-detector setup. Figures of merit were obtained, by comparing the results from the multi detector approach outlined above, with results from batch-DLS and transmission electron microscopy (TEM). Furthermore, validation performed with certified NIST Au-NP showed excellent agreement. The developed methods show potential for characterization of other commonly used and important metallic engineered nanoparticles.

Nature of alpha and beta particles in glycogen using molecular size distributions

Glycogen is a randomly hyperbranched glucose polymer. Complex branched polymers have two structural levels: individual branches and the way these branches are linked. Liver glycogen has a third level: supramolecular clusters of beta particles which form larger clusters of alpha particles. Size distributions of native glycogen were characterized using size exclusion chromatography (SEC) to find the number and weight distributions and the size dependences of the number- and weight-average masses. These were fitted to two distinct randomly joined reference structures, constructed by random attachment of individual branches and as random aggregates of beta particles. The z-average size of the alpha particles in dimethylsulfoxide does not change significantly with high concentrations of LiBr, a solvent system that would disrupt hydrogen bonding. These data reveal that the beta particles are covalently bonded to form alpha particles through a hitherto unsuspected enzyme process, operative in the liver on particles above a certain size range.

A bayesian approach for quantifying trace amounts of antibody aggregates by sedimentation velocity analytical ultracentrifugation

Sedimentation velocity analytical ultracentrifugation (SV-AUC) has become an important tool for the characterization of the purity of protein therapeutics. The work presented here addresses a need for methods orthogonal to size-exclusion chromatography for ensuring the reliable quantitation of immunogenic oligomers, for example, in antibody preparations. Currently the most commonly used approach for SV-AUC analysis is the diffusion-deconvoluted sedimentation coefficient distribution c(s) method, previously developed by us as a general purpose technique and implemented in the software SEDFIT. In both practical and theoretical studies, different groups have reported a sensitivity of c(s) for trace oligomeric fractions well below the 1% level. In the present work we present a variant of c(s) designed for the purpose of trace detection, with customized Bayesian regularization. The original c(s) method relies on maximum entropy regularization providing the most parsimonious distribution consistent with the data. In the present paper, we use computer simulations of an antibody system as example to demonstrate that the standard maximum entropy regularization, due to its design, leads to a theoretical lower limit for the detection of oligomeric traces and a consistent underestimate of the trace populations by approximately 0.1% (dependent on the level of regularization). This can be overcome with a recently developed Bayesian extension of c(s) (Brown et al., Biomacromolecules, 8:2011-2024, 2007), utilizing the known regions of sedimentation coefficients for the monomer and oligomers of interest as prior expectation for the peak positions in the distribution. We show that this leads to more clearly identifiable and consistent peaks and lower theoretical limits of quantization by approximately an order of magnitude for some experimental conditions. Implications for the experimental design of SV-AUC and practical detection limits are discussed.

Multiplexed affinity-based protein complex purification

Here we proved the principle of a multiplexed affinity-based protein complex purification (MAPcP) technique that targets simultaneous extraction of multiple protein complexes with superior purity. Microspheres of various sizes and coupled with different affinity probes extract several protein complexes concurrently and specifically. After the coextraction, flow-field flow fractionation (Fl-FFF) rapidly washes the microspheres as well as separates them based on their sizes to recover the clean individual complex for downstream analysis. Demonstration of the parallel extraction of two immuno-complexes from the yeast whole cell lysate showed that MAPcP can enhance the sample purity significantly compared to the traditional centrifugation and magnetic pull-down methods used for small scale protein purification. Simultaneous isolation of multiple protein complexes can facilitate the elucidation of the functional relationship among protein complexes and improve our understanding of the biological network.

A two-dimensional suspension array system by coupling field flow fractionation to flow cytometry

Flow field flow fractionation (Fl-FFF) was coupled to flow cytometry to improve the performance of suspension arrays. Size-based separation of the protein-conjugated microspheres by Fl-FFF was performed and the results demonstrated that, the separation could tolerate a wide range of carrier fluid conditions (pH values, salt concentrations, and buffer compositions) favorable for immunoassays. The immuno-complex remained intact during Fl-FFF, as revealed by fluorescence measurements before and after the Fl-FFF separation, and SDS-PAGE of the eluted proteins. The sample throughput of the suspension array can be increased several folds by using particles of different sizes and separating them with Fl-FFF before flow cytometric measurement. Moreover, the gel result hinted that the continuous wash inside the Fl-FFF system may lower the assay background, another possible advantage of the two-dimensional suspension array system.

Asymmetrical flow field-flow fractionation coupled to multiangle laser light scattering detector: optimization of crossflow rate, carrier characteristics, and injected mass in alginate separation

The coupling of the flow field-flow fractionation (FlFFF) to differential refractive index (DRI) and multiangle laser light scattering (LS) detectors is a powerful tool for characterizing charged polysaccharides such as alginate. However, the correct interpretation of the experimental results and extrapolation of meaningful molecular parameters by using an analytical tool with such a level of complexity requires improvement of the knowledge of the alginate behavior in the channel and careful optimization of the operating conditions. Therefore, the influence of the critical operating parameters, such as crossflow rate, carrier composition and concentration, and sample load, on the alginate retention was carefully evaluated. Combined information obtained simultaneously by DRI and LS detectors over the wide range of the crossflow rate, carrier liquid concentration, and injected amount, allowed to set the appropriate combination of optimal parameters. It was found that the crossflow rate of 0.25 mL/min, carrier solution containing 5x10(-2 )mol/L ammonium or sodium chloride, and 50-100 microg of injected sample mass were necessary to achieve complete separation and determination of the meaningful molecular characteristics. The values of the weight-average hydrodynamic radius (R(Hw)), radius of gyration (R(G)), and molar mass (M), obtained under the optimal conditions were in good agreement to those found for alginates in the literature.