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Extracellular vesicles are small membrane-bound structures that are released by cells and play important roles in intercellular communication garnering significant attention in scientific society recently due to their potential as diagnostic and therapeutic tools. However, separating EVs from large-volume samples remains a challenge due to their small size and low concentration. In this manuscript, we presented a novel method for separating polystyrene beads as control and extracellular vesicles from large sample volumes using bifurcated asymmetric field flow fractionation in PDMS-free microfluidic devices. Separation characteristics were evaluated using the control system of polystyrene bead mix, which offers up to 3.7X enrichment of EV-sized beads. Furthermore, in the EV-sample from bioreactor culture media, we observed a notable population distribution shift of extracellular vesicles. Herein presented novel PDMS-free microfluidic device fabrication protocol resulted in devices with reduced EV-loss compared to size-exclusion columns. This method represented an improvement over the current state of the art in terms of EV separation from large sample volumes through the use of novel field flow fractionation design. [ABSTRACT FROM AUTHOR]

While the exact health risks associated with nanoplastics are currently the focus of intense research, there is no doubt that humans are exposed to nanoplastics and that food could be a major source of exposure. Nanoplastics are released from plastic materials and articles used during food production, processing, storage, preparation, and serving. They are also likely to enter the food chain via contaminated water, air, and soil. However, very limited exposure data for risk assessment exists so far due to the lack of suitable analytical methods. Nanoplastic detection in food poses a great analytical challenge due to the complexity of plastics and food matrices as well as the small size and expectedly low concentration of the plastic particles. Multidetector field flow fractionation has emerged as a valuable analytical technique for nanoparticle separation over the last decades, and the first studies using the technique for analyzing nanoplastics in complex matrices are emerging. In combination with online detectors and offline analysis, multidetector field flow fractionation is a powerful platform for advanced characterization of nanoplastics in food by reducing sample complexity, which otherwise hampers the full potential of most analytical techniques. The focus of this article is to present the current state of the art of multidetector field flow fractionation for nanoplastic analysis and to discuss future trends and needs aiming at the analysis of nanoplastics in food. [ABSTRACT FROM AUTHOR]

The study of the properties and composition of natural nanoparticles is an essential problem in analytical chemistry. Currently, there are no reference samples of natural nanoparticles, which complicates the study of the role of nanoparticles in specific processes, including geochemical ones, and makes it almost impossible to compare the results obtained by different researchers. In this work, nanoparticles of kaolinite, montmorillonite, and muscovite are studied as potential reference samples of natural nanoparticles. A complex of analytical methods has been proposed for the isolation and characterization of mineral nanoparticles, including the field flow fractionation of particles in a rotating coiled column, laser diffraction, scanning electron microscopy, and inductively coupled plasma atomic emission spectrometry. According to laser diffraction data, 93–98% of the isolated particles are from 40 to 300 nm in size; 2–7% of particles have sizes of up to 830 nm. The sizes of the isolated particles were confirmed by scanning electron microscopy. Based on the aluminum content, the concentrations of mineral nanoparticles in the isolated suspensions were estimated. The aggregation stability of nanoparticles in 5 mM phosphate buffer solutions of pH 6, 7, and 8 was studied. Muscovite nanoparticles are stable at pH 7 and 8 for at least 4 weeks, while montmorillonite nanoparticles have similar stability only at pH 8. For kaolinite nanoparticles, significant aggregation was observed at all studied pH values of buffer solutions. The obtained experimental results made it possible to clarify the problems and assess the prospects for developing reference samples of natural nanoparticles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Resveratrol (RSV) is a naturally occurring polyphenolic phytoalexin with beneficial effects on human health, including the treatment and prevention of ulcerative colitis and cancer. This work proposes the formulation and characterization of new nanoparticles (NPs) for the specific colon delivery of RSV. RSV was encapsulated in zein (Z) NPs, coated by a hydrophilic pectin (P) shell to significantly increase the dissolution rate of RSV in aqueous environments. Since the dissolved drug was strongly degraded in a simulated gastrointestinal tract, the ZP-NPs were coated with Eudragit S 100. The coated particles, even if aggregated, had a spherical morphology with diameters in the 100–200 nm range. Release studies of RSV from the ZP coated NPs evidenced their potential ability to induce a specific colon delivery of this drug so that this formulation can be proposed to enrich natural food products to enhance their preventive and therapeutic effects in the lower GI tract. [ABSTRACT FROM AUTHOR]

Applications of asymmetrical flow field-flow fractionation (AF4) continue to expand rapidly in the fields of nanotechnology and biotechnology. In particular, AF4 has proven valuable for the separation and analysis of particles, biomolecular species (e.g., proteins, bacteria) and polymers (natural and synthetic), ranging in size from a few nanometers to several micrometers. The separation of non-spheroidal structures (e.g., rods, tubes, etc.) with primary dimensions in the nanometer regime, is a particularly challenging application deserving of greater study and consideration. The goal of the present study was to advance current understanding of the mechanism of separation of rod-like nano-objects in the AF4 channel. To achieve this, we have systematically investigated a series of commercially available cetyltrimethylammonium bromide stabilized gold nanorods (AuNRs), with aspect ratios from 1.7 to 10. Results show clearly that the retention time is principally dependent on the translational diffusion coefficient of the AuNRs. Equations used to calculate translational and rotational diffusion coefficients (cylinder and prolate ellipsoid models) yield similarly good fits to experimental data. Well characterized gold nanorods (length and diameter by transmission electron microscopy) can be used as calibrants for AF4 measurements allowing one to determine the aspect ratio of nanorod samples based on their retention times.ᅟ [ABSTRACT FROM AUTHOR]

The use of nanotechnology in medical products has been demonstrated at laboratory scale, and many resulting nanomedicines are in the translational phase toward clinical applications, with global market trends indicating strong growth of the sector in the coming years. The translation of nanomedicines toward the clinic and subsequent commercialization may require the development of new or adaptation of existing standards to ensure the quality, safety and efficacy of such products. This work addresses some identified needs, and illustrates the shortcomings of currently used standardized methods when applied to medical-nanoparticles to assess particle size, drug loading, drug release and in vitro safety. Alternative physicochemical, and in vitro toxicology methods, with the potential to qualify as future standards supporting the evaluation of nanomedicine are provided. [ABSTRACT FROM AUTHOR]

In the last 10 years, asymmetrical flow field flow fractionation (AF4) has been one of the most promising approaches to characterize colloidal particles. Nevertheless, despite its potentialities, it is still considered a complex technique to set up, and the theory is difficult to apply for the characterization of complex samples containing submicron particles and nanoparticles. In the present work, we developed and propose a simple analytical strategy to rapidly determine the presence of several submicron populations in an unknown sample with one programmed AF4 method. To illustrate this method, we analyzed polystyrene particles and fullerene aggregates of size covering the whole colloidal size distribution. A global and fast AF4 method (method O) allowed us to screen the presence of particles with size ranging from 1 to 800 nm. By examination of the fractionating power F , as proposed in the literature, convenient fractionation resolution was obtained for size ranging from 10 to 400 nm. The global F values, as well as the steric inversion diameter, for the whole colloidal size distribution correspond to the predicted values obtained by model studies. On the basis of this method and without the channel components or mobile phase composition being changed, four isocratic subfraction methods were performed to achieve further high-resolution separation as a function of different size classes: 10-100 nm, 100-200 nm, 200-450 nm, and 450-800 nm in diameter. Finally, all the methods developed were applied in characterization of nanoplastics, which has received great attention in recent years. [ABSTRACT FROM AUTHOR]

Field flow fractionation (FFF) techniques are used to successfully characterize several nanomaterials by sizing nano-entities and producing information about the aggregation/agglomeration state of nanoparticles. By coupling FFF techniques to specific detectors, researchers can determine particle-size distributions (PSDs), expressed as mass-based or number-based PSDs. This review considers FFF applications in the food, biomedical, and environmental sectors, mostly drawn from the past 4 y. It thus underlines the prominent role of asymmetrical flow FFF within the FFF family. By concisely comparing FFF techniques with other techniques suitable for sizing nano-objects, the advantages and the disadvantages of these instruments become clear. A consideration of select recent publications illustrates the state of the art of some lesser-known FFF techniques and innovative instrumental set-ups. [ABSTRACT FROM AUTHOR]

In the present investigation, styrene-acrylic and pure acrylic emulsions used in water-based decorative coatings are characterized by size exclusion chromatography (SEC) and asymmetric flow field-flow fractionation (AF4). Both the separation techniques are coupled online to multiangle laser light scattering (MALLS) and refractive index detection to investigate the molar mass properties during the course of the free radical polymerization reaction. For the acrylic emulsion, kinetic samples are taken from the reactor at fixed time intervals and analyzed. In SEC-MALLS, unusual elution behavior is observed which is found previously for highly branched polymer species. In contrast, the AF4 fractograms indicate normal mode elution without any unusual behavior as compared to the SEC analyses. The molar masses obtained by AF4 are significantly higher compared to the SEC results. Further, AF4 is used to determine the gel contents of the kinetic samples of the acrylic emulsion and for both the acrylic and styrene-acrylic emulsions, AF4 proves to be a robust and feasible tool allowing for improved correlations of the molecular and materials properties of water-based polymer emulsions. [ABSTRACT FROM AUTHOR]

The control of gold nanorod (GNR) solution-based syntheses has been hindered in part by the inability to examine and control the conversion of precursor seed populations to anisotropic materials, which have resulted in low yields of desired products and limited their commercial viability. The advantages offered by tandem separation and characterization methods utilizing asymmetric-flow field flow fractionation (A4F) are principally achieved as a result of their non-disruptive nature (minimizing artefacts), fast throughput, and in-situ analysis. With hyphenated A4F methods, resolved populations of seeds and secondary products, up to long aspect ratio rods, have been achieved and exemplify progress towards elucidating mechanistic aspects of formation and thus rational design. While there have been previously reported studies on A4F separation of GNRs, to our knowledge, this is the first published investigation of in situ GNR growth, separation, and characterization based on A4F, where its utilization in this capacity goes beyond traditional separation analysis. By using hydroquinone as the reducing agent, the conversion of the initial seed population to a distribution of products, including the GNRs, could be monitored in real time using A4F hyphenated with a diode array detector. Transmission electron microscopy confirms that the number of peaks observed during fractionation corresponds with size and shape dispersity. This proof-of-principle study introduces A4F as a technique that establishes a foundation for future mechanistic studies on the growth of GNRs from gold seeds, including conversion of the seed population to initial products, a topic highly relevant to advancing progress in nanomanufacturing. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Electrical Field Flow Fractionation (ElFFF) is a sub method in the field flow fractionation (FFF) family that relies on an applied voltage on the channel walls to effect a separation. ElFFF has fallen behind some of the other FFF methods because of the optimization complexity of its experimental parameters. To enable better optimization, a particle based model of the ElFFF systems has been developed and is presented in this work that allows the optimization of the main separation parameters, such as electric field magnitude, frequency, duty cycle, offset, flow rate and channel dimensions. The developed code allows visualization of individual particles inside the separation channel, generation of realistic fractograms, and observation of the effects of the various parameters on the behavior of the particle cloud. ElFFF fractograms have been generated via simulations and compared with experiments for both normal and cyclical ElFFF. The particle visualizations have been used to verify that high duty cycle voltages are essential to achieve long retention times and high resolution separations. Furthermore, by simulating the particle motions at the channel outlet, it has been demonstrated that the top channel wall should be selected as the accumulation wall for cyclical ElFFF to reduce band broadening and achieve high efficiency separations. While the generated particle based model is a powerful tool to estimate the outcomes of the ElFFF experiments and visualize particle motions, it can also be used to design systems with new geometries which may lead to the design of higher efficiency ElFFF systems. Furthermore, this model can be extended to other FFF techniques by replacing the electrical field component of the model with the fields used in the other FFF techniques. [ABSTRACT FROM AUTHOR]

This review discusses some recent work on the microstructure analysis of complex polymers using advanced fractionation methods. Complex polymers are distributed in a number of molecular parameters including molar mass, chemical composition, molecular architecture, and microstructure. Molar mass and chemical composition analysis is typically conducted by a range of spectroscopic and chromatographic methods, size exclusion chromatography and high-performance liquid chromatography (HPLC) being the most important fractionation methods. It is shown that HPLC is also very sensitive regarding polymer microstructure and can be used for the fractionation of e.g. polymethacrylates, polyisoprene, and polybutadiene. The best approach to the quantitative analysis of microstructure distributions is the on-line coupling of the fractionation with 1H nuclear magnetic resonance spectroscopy. The spectroscopic analysis of chromatographic fractions provides concentration profiles of the tactic units as a function of the chromatographic separation and can be used for both HPLC and size exclusion chromatography. Apart from column-based fractionations, channel-based fractionations such as thermal field flow fractionation are powerful tools for microstructure analysis of complex polymers. It has been shown very recently that thermal field flow fractionation is capable of fractionating polyisoprene and polybutadiene according to microstructure. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Proteins are separated in field flow fractionation (FFF) according to a well-established mechanism described as the 'Normal or Brownian' mode. In the case of the sub-technique using a hollow fiber, the focalization/relaxation position can be observed visually only with a transparent holder and using dyes as samples. Whatever the choice of instrumentation, a dye-free method is proposed to determine the center of the zone from experimental fractograms by means of only two sample elutions. It is also possible to determine and model the kinematics of the sample toward the equilibrium focalization/relaxation position as well as the real dimensions of the fiber during the separation process. [ABSTRACT FROM AUTHOR]

Exosomes participate in cancer metastasis, but studying them presents unique challenges as a result of their small size and purification difficulties. Asymmetrical field flow fractionation with in-line ultraviolet absorbance, dynamic light scattering, and multi-angle light scattering was applied to the size separation and characterization of non-labeled B16-F10 exosomes from an aggressive mouse melanoma cell culture line. Fractions were collected and further analyzed using batch mode dynamic light scattering, transmission electron microscopy and compared with known size standards. Fractogram peak positions and computed radii show good agreement between samples and across fractions. Ultraviolet absorbance fractograms in combination with transmission electron micrographs were able to resolve subtle heterogeneity of vesicle retention times between separate batches of B16-F10 exosomes collected several weeks apart. Further, asymmetrical field flow fractionation also effectively separated B16-F10 exosomes into vesicle subpopulations by size. Overall, the flow field flow fractionation instrument combined with multiple detectors was able to rapidly characterize and separate exosomes to a degree not previously demonstrated. These approaches have the potential to facilitate a greater understanding of exosome function by subtype, as well as ultimately allow for 'label-free' isolation of large scale clinical exosomes for the purpose of developing future exosome-based diagnostics and therapeutics. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The development of highly efficient asymmetric-flow field flow fractionation (A4F) methodology for biocompatible PEGylated gold nanorods (GNR) without the need for surfactants in the mobile phase is presented. We report on the potential of A4F for rapid separation by evaluating the efficiency of functionalized surface coverage in terms of fractionation, retention time ( t) shifts, and population analysis. By optimizing the fractionation conditions, we observed that the mechanism of separation for PEGylated GNRs by A4F is the same as that for CTAB stabilized GNRs (i.e., according to their AR) which confirms that the elution mechanism is not dependent on the surface charge of the analytes and/or the membrane. In addition, we demonstrated that A4F can distinguish different surface coverage populations of PEGylated GNRs. The data established that a change in M of the functional group and/or surface orientation can be detected and fractionated by A4F. The findings in this study provide the foundation for a complete separation and physicochemical analysis of GNRs and their surface coatings, which can provide accurate and reproducible characterization critical to advancing biomedical research. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The objective of this study was to show that on-line asymmetric flow-field flow fractionation (AFFFF)-multidetection coupling is useful for studying environmental colloids in a qualitative and quantitative way. The utility of the technique was illustrated by assessing the colloidal fraction of the copper that was extracted from the soil, transferred to an aqueous phase and then transported by drain waters in a wine-growing area. To determine the size and composition of the colloids, AFFFF was coupled to UV, multi-angle light scattering and inductively coupled plasma mass spectrometry detectors. Colloidal copper represents between 20 and 60 % of the total copper in the sub 450 nm of drain waters. Copper is mainly associated with organic-rich colloids with a size below 10 nm. It is also found in organo-mineral populations (as clay or (oxy)hydroxides), with sizes ranging between 10 and 450 nm. [ABSTRACT FROM AUTHOR]

A method of analysis of silver nanoparticles (AgNPs) in chicken meat was developed. The homogenized chicken meat sample, which was spiked with AgNPs, was subjected to enzymolysis by Proteinase K for 40 min at 37 °C. Transmission electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) in single particle mode were used to characterize the number-based size distribution of AgNPs in the meat digestate. Because similar size distributions were found in the meat digestate and in the aqueous suspension of AgNPs used for spiking the meat, it was shown that no detectable dissolution of the AgNPs took place during the sample preparation stage. The digestate was injected into the asymmetric flow field flow fractionation (AF) -ICP-MS system, which enabled fractionation of nanoparticles from the remaining meat matrix, and resulted in one large peak in the fractograms as well as two smaller peaks eluting close to the void volume. The recovery of silver contained in the large AgNP peak was around 80 %. Size determination of AgNPs in the meat matrix, based on external size calibration of the AF channel, was hampered by non-ideal (early elution) behavior of the AgNPs. Single particle ICP-MS was applied for determination of the number-based particle size distribution of AgNPs in collected fractions. The presented work describes for the first time the coupling of AF and ICP-MS for AgNP separation in a food matrix. [ABSTRACT FROM AUTHOR]

This study investigated the effect of UV irradiation on the characteristics and toxicity of 50 nm (nominal diameter) polyvinylpyrrolidone-capped silver nanoparticles (AgNPs) in the presence and absence of dissolved organic carbon (DOC). The photolysis resulted in a decrease in average particle size as measured by field flow fractionation interfaced with inductively coupled plasma mass spectrometry. The decrease in size was attributed to the photo-induced oxidation of the PVP and dissolution of metallic silver. Moreover, photolysis of the AgNPs in solutions containing DOC appeared to give rise to small nanoparticles (~5 nm) formed via reduction of dissolved silver ions. These results were consistent with photolysis of AgNO solutions initially devoid of nanoparticles. Thus, the carbon-containing constituents of DOC serve as reducing agents for Ag, primarily under conditions of UV irradiation. The standard zooplankton model, Daphnia magna, indicated that the toxicity of nanosilver was significantly reduced when the AgNPs have been exposed to UV light. Observed toxicity was further reduced when AgNPs in DOC-containing solutions were exposed to UV. These results suggest that environmentally relevant conditions such as DOC and UV light are important mitigating factors that mediate the aquatic toxicity of AgNPs. [ABSTRACT FROM AUTHOR]

The application of asymmetric-flow field flow fractionation (A4F) for low aspect ratio gold nanorod (GNR) fractionation and characterization was comprehensively investigated. We report on two novel aspects of this application. The first addresses the analytical challenge involved in the fractionation of positively charged nanoparticles by A4F, due to the interaction that exists between the negatively charged native membrane and the analyte. We show that the mobile phase composition is a critical parameter for controlling fractionation and mitigating the membrane-analyte interaction. A mixture of ammonium nitrate and cetyl trimethyl ammonium bromide at different molar ratios enables separation of GNRs with high recovery. The second aspect is the demonstration of shape-based separation of GNRs in A4F normal mode elution (i.e., Brownian mode). We show that the elution of GNRs is due both to aspect ratio and a steric-entropic contribution for GNRs with the same diameter. This latter effect can be explained by their orientation vector inside the A4F channel. Our experimental results demonstrate the relevance of the theory described by Beckett and Giddings for non-spherical fractionation (Beckett and Giddings, J Colloid and Interface Sci 186(1):53-59, ). However, it is shown that this theory has its limit in the case of complex GNR mixtures, and that shape (i.e., aspect ratio) is the principal material parameter controlling elution of GNRs in A4F; the apparent translational diffusion coefficient of GNRs increases with aspect ratio. Finally, the performance of the methodology developed in this work is evaluated by the fractionation and characterization of individual components from a mixture of GNR aspect ratios. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial research. One consequence of the development of new ˵tailor-made″ polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass, molecular topology and chemical composition distribution. This review presents different new and relevant techniques for polyolefin analysis. The analysis of copolymers by combining high-temperature SEC and FTIR spectroscopy yields information on chemical composition and molecular topology as a function of molar mass. Crystallization based fractionation techniques are powerful methods for the analysis of short-chain branching in LLDPE and the analysis of polyolefin blends. These methods include temperature-rising elution fractionation, crystallization analysis fractionation and the recently developed crystallization-elution fractionation. The latest development in the field of polyolefin fractionation is high-temperature interaction chromatography. Based on the principles of gradient HPLC and liquid chromatography at critical conditions this method is used for fast analysis of the chemical composition distribution of complex olefin copolymers. The efficiency of HPLC based systems for the separation of various olefin copolymers will be discussed. The ultimate development in high-temperature fractionation of polyolefins is comprehensive high-temperature two-dimensional liquid chromatography. The review will discuss some of the pioneering work that has been done since 2008. Finally, the correlation between molar mass and chemical composition can be accessed by on-line coupling of high-temperature SEC and 1H-NMR spectroscopy. It is shown that the on-line NMR analysis of chromatographic fractions from high-temperature fractionations is possible and yields information on microstructure and tacticity in addition to molar mass and copolymer composition. [ABSTRACT FROM AUTHOR]

Molecular weight, distribution, as well as other molecular characteristics are important drivers in determining the potential behaviors and hence applications of polymeric materials. Out of different methods available for the determination of molecular weight and its distribution, field flow fractionation (FFF) provides absolute molecular weight values and accurate molecular weight distributions. Analytical ultracentrifugation (AUC), on the other hand, relies on the exact density of the polymer materials in solution to determine the accurate molecular weight and its distribution and in the absence of knowledge of exact density, AUC is less accurate than the FFF method. However, combination of the two methods can be achieved to gain insights into the other molecular characteristics of swollen polymer chains. One such example is the determination of the exact density of the swollen polymer chains by the incorporation of the molecular weight information from FFF into AUC analysis. Based on the comparison of the optimized polymer chain density with the bulk density, it was observed that the polyacrylic acid and polyacrylamide chains were swollen in the range of 27 to 29%. Moreover, the FFF and AUC can also complement each other in enhancing the range of characterization possible with the two methods when used separately. [ABSTRACT FROM PUBLISHER]

Purpose: Stability of polymeric micelles upon injection is essential for a drug delivery system but is not fully understood. We optimized an analytical test allowing quantification of micellar stability in biofluids and applied it to a variety of block copolymer micelles with different hydrophobic block architechtures. Methods: Polymeric micelles were prepared from four different polymers and investigated via encapsulation of two fluorescent dyes. Samples were incubated in human serum; changes in Foerster Resonance Energy Transfer (FRET) were recorded as a function of time. This fluorescence-based approach was supported semi-quantitatively by results from Asymmetrical Flow Field-Flow-Fractionation (AF4). Results: After incubation experiments, micellar stability was determined by calculation of two stability-indicating parameters: residual micellar fractions (RMFs) and in vitro serum half-lives. Both parameters showed that PEG-PVPy micelles rapidly destabilized after 3 h (RMF < 45%), whereas PEG-PLA, PEG-PLGA and PEG-PCL micelles were far more stable (RMFs 65 to 98%). Conclusion: This FRET-based assay is a valuable tool in evaluating and screening serum stability of polymeric micelles and revealed low serum stability of PEG-PVPy micelles compared to polyester-based micelles. [ABSTRACT FROM AUTHOR]

ymmetrical-flow field flow fractionation (AFFF) separates constituents based on hydrodynamic size and is emerging as a powerful tool for obtaining high-resolution information on the size, molecular weight, composition, and stability of nanoscale particles in liquid media. We employ a customized AFFF system combining on-line detectors for multi-angle light scattering, dynamic light scattering, and UV-Vis absorption. Our objective is to develop optimized measurement protocols for the characterization of gold nanoparticles (GNPs), which are widely utilized in biomedical research and other nanotechnology applications. Experimental conditions have been optimized by controlling key parameters, including injection volume and solids concentration, mobile phase composition, membrane type and pore size, and ratio of channel-to-cross-flow rates. Individual citrate-stabilized GNP components (nominally 10, 20, 30, 40, and 60 nm) and GNPs functionalized with polyethylene glycol were separated from multicomponent GNP mixtures by AFFF and subsequently characterized. We discuss the effects due to variations in measurement parameters and GNP surface modification on observed retention, recovery, and peak resolution. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

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We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter. [ABSTRACT FROM AUTHOR]

Numerical simulation results for characteristics of separating multiple kinds of magnetic particles with different magnetic susceptibility by magnetic chromatography using high temperature superconducting bulk magnet are presented in this paper. The transient particle transport process of two kinds of particles with different magnetic, susceptibility are numerically simulated. The calculated time evolutions of the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field produced by the highly magnetized high temperature superconducting bulk magnet show the flow velocity difference of the particle transport corresponding to the difference of the magnetic susceptibility. The numerical results also show that the separation of paramagnetic particles of 20 nm diameter is possible. [ABSTRACT FROM AUTHOR]

In this review, field-flow fractionation (FFF) is presented as a versatile and powerful analytical technique for separation and characterization of different sample types. The underlying principles of FFF separation theory including sources of the obstacles and the difficulties as well as the new approaches is also introduced. This paper describes FFF sub-techniques, presents its exemplary application and the future trends in development of FFF techniques. [ABSTRACT FROM AUTHOR]

The current status of elemental speciation using inductively coupled plasma-mass spectrometry (ICP-MS) as the method of detection is examined in this paper. Manuscripts that describe specific speciation applications using on-line hyphenation of gas chromatography (GC), liquid chromatography (LC), capillary electrophoresis (CE), and field flow fractionation (FFF) with ICP-MS detection are presented. This review covers the application papers published between January 2000 and December 2003. Evaluation of the current literature shows that LC is the most prevalent separation technique for elemental speciation followed by CE, GC, and FFF, respectively. [ABSTRACT FROM AUTHOR]

This paper describes the development of an integrated system using a dry film resistant (DFR) microfluidic channel consisting of pulsed field dielectrophoretic field-flow-fractionation (DEP-FFF) separation and optical detection. The prototype chip employs the pulse DEP-FFF concept to separate the cells (Escherichia coli and Saccharomyces cerevisiae) from a continuous flow, and the rate of release of the cells was measured. The separation experiments were conducted by changing the pulsing time over a pulsing time range of 2–24 s and a flow rate range of 1.2–9.6 μ L min − 1 . The frequency and voltage were set to a constant value of 1 M Hz and 14 V pk-pk, respectively. After cell sorting, the particles pass the optical fibre, and the incident light is scattered (or absorbed), thus, reducing the intensity of the transmitted light. The change in light level is measured by a spectrophotometer and recorded as an absorbance spectrum. The results revealed that, generally, the flow rate and pulsing time influenced the separation of E. coli and S. cerevisiae. It was found that E. coli had the highest rate of release, followed by S. cerevisiae. In this investigation, the developed integrated chip-in-a lab has enabled two microorganisms of different cell dielectric properties and particle size to be separated and subsequently detected using unique optical properties. Optimum separation between these two microorganisms could be obtained using a longer pulsing time of 12 s and a faster flow rate of 9.6 μ L min − 1 at a constant frequency, voltage, and a low conductivity. [ABSTRACT FROM AUTHOR]