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Extracellular vesicles (EVs) have emerged as a promising tool for clinical liquid biopsy. However, the identification of EVs derived from blood samples is hindered by the presence of abundant plasma proteins, which impairs the downstream biochemical analysis of EV‐associated proteins and nucleic acids. Here, we employed optimized asymmetric flow field‐flow fractionation (AF4) combined with density cushion ultracentrifugation (UC) to obtain high‐purity and intact EVs with very low lipoprotein contamination from human plasma and serum. Further proteomic analysis revealed more than 1000 EV‐associated proteins, a large proportion of which has not been previously reported. Specifically, we found that cell‐line‐derived EV markers are incompatible with the identification of plasma‐EVs and proposed that the proteins MYCT1, TSPAN14, MPIG6B and MYADM, as well as the traditional EV markers CD63 and CD147, are plasma‐EV markers. Benefiting from the high‐purity of EVs, we conducted comprehensive miRNA profiling of plasma EVs and nanosized particles (NPs), as well as compared plasma‐ and serum‐derived EVs, which provides a valuable resource for the EV research community. Overall, our findings provide a comprehensive assessment of human blood EVs as a basis for clinical biopsy applications. [ABSTRACT FROM AUTHOR]

Colloids can facilitate the transport of trace elements in soil, but earlier studies fell short either because of sampling artefacts or because no contrasting soils were used; both factors hamper a better understanding of where this occurs. Here, leaching in undisturbed and unsaturated soil columns was observed to identify colloidal transport of cadmium (Cd) and uranium (U) in soils with contrasting properties. Crucially, it was examined how such column data relate to more traditional in situ data obtained with porous suction cups. Soils were collected from three agricultural fields in Switzerland (soil pH 5.1–7.3), leached during 36 days (0.6 pore volumes, ~1.6 mm day−1), and elements trapped in the PTFE suction plates were recovered and were ascribed to colloids. Of the total mobile mass (sum percolate and plate), 18%–53% (Cd) or 8–89% (U) was retained by plates, the range depending on the field where soil was sampled and that fraction depends on soil pH and for U also on dissolved inorganic carbon. The total mobile Cd or U mass divided by the percolated volume indicates the metal concentration in the average leachate and was logically highest for Cd in the most acidic soil and for U in the most alkaline soil. The concentrations of Cd and U in these column leachates were >10‐fold higher than corresponding concentrations in the suction cups in the field for those soils and elements where colloids dominated leaching. In contrast, they were within a factor of two where colloids are <20% of the mobile mass. Flow Field‐Flow Fractionation (FlFFF) analyses showed an association of colloidal U with oxyhydroxides, clays and organic matter and, for colloidal Cd, an association with organic matter. These data show that suction cups or filtered percolates can underestimate the leaching of Cd and U by up to an order of magnitude. [ABSTRACT FROM AUTHOR]

Liposome development is of great interest owing to increasing requirements for efficient drug carriers. The structural features and thermal stability of such liposomes are crucial in drug transport and delivery. Reported here are the results of the structural characterization of PEGylated liposomes via small‐ and wide‐angle X‐ray scattering and an asymmetric flow field‐flow fractionation (AF4) system coupled with differential refractive‐index detection, multi‐angle light scattering (MALS) and dynamic light scattering. This integrated analysis of the exemplar PEGylated liposome formed from hydrogenated soy phosphatidylcholine (HSPC) with the addition of cholesterol reveals an average hydrodynamic radius (Rh) of 52 nm with 10% polydispersity, a comparable radius of gyration (Rg) and a major liposome particle mass of 118 kDa. The local bilayer structure of the liposome is found to have asymmetric electronic density profiles in the inner and outer leaflets, sandwiched by two PEGylated outer layers ca 5 nm thick. Cholesterol was found to effectively intervene in lipid chain packing, resulting in the thickening of the liposome bilayer, an increase in the area per lipid and an increase in liposome size, especially in the fluid phase of the liposome. These cholesterol effects show signs of saturation at cholesterol concentrations above ca 1:5 cholesterol:lipid molar ratio. [ABSTRACT FROM AUTHOR]

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To predict the polymer properties produced by free‐radical polymerization of N‐vinylpyrrolidone (NVP) in aqueous solution a detailed kinetic model has been developed. The kinetic model allows to calculate the chain length distribution, the number of branching points, and the number of terminal double bonds (TDB). The latter is accounted for since TDBs are a precondition for branching. While monomer conversion can be predicted sufficiently using independently determined rate constants for propagation and termination, here the predictions of structural properties by a newly developed extended kinetic model to experimental findings are compared. Polymer produced in a continuous stirred tank reactor is analyzed by gel permeation chromatography (GPC), field flow fractionation (FFF), and high‐pressure liquid chromatography (HPLC). [ABSTRACT FROM AUTHOR]

Exosomes (small extracellular vesicles) in living organisms play an important role in processes such as cell proliferation or intercellular communication. Recently, exosomes have been extensively investigated for biomarker discoveries for various diseases. An important aspect of exosome analysis involves the development of enrichment methods that have been introduced for successful isolation of exosomes. These methods include ultracentrifugation, size exclusion chromatography, polyethylene glycol‐based precipitation, immunoaffinity‐based enrichment, ultrafiltration, and asymmetric flow field‐flow fractionation among others. To confirm the presence of exosomes, various characterization methods have been utilized such as Western blot analysis, atomic force microscopy, electron microscopy, optical methods, zeta potential, visual inspection, and mass spectrometry. Recent advances in high‐resolution separations, high‐performance mass spectrometry and comprehensive proteome databases have all contributed to the successful analysis of exosomes from patient samples. Herein we review various exosome enrichment methods, characterization methods, and recent trends of exosome investigations using mass spectrometry‐based approaches for biomarker discovery. [ABSTRACT FROM AUTHOR]

Photo‐iniferter reversible addition‐fragmentation chain transfer (PI‐RAFT) polymerization of N‐vinylformamide (NVF) is demonstrated by using purple light. PNVFs with predetermined molar masses and narrow molar mass distributions are obtained. High RAFT chain‐end fidelity is confirmed by matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) and electrospray‐ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS), and chain extension experiment. To demonstrate the potential of this approach, an original poly(N‐vinylpyrrolidone)‐b‐poly(N‐vinylformamide) (PVP‐b‐PNVF) diblock copolymer is synthesized and characterized by aqueous size‐exclusion chromatography (SEC), asymmetric flow field‐flow fractionation (A4F), and 1H diffusion‐ordered spectroscopy nuclear magnetic resonance (1H DOSY NMR). Finally, selective hydrolysis of PNVF block to corresponding pH‐responsive poly(N‐vinylpyrrolidone)‐b‐poly(N‐vinylformamide) (PVP‐b‐PVAm) is performed. [ABSTRACT FROM AUTHOR]

Post‐loading of polymersomes with different bio(macro)molecules has been successfully demonstrated, thus mimicking the diffusion processes through biological membranes. However, it is still an open issue the extent to which this diffusion process leads to transmembrane transportation, or rather encapsulation of cargo within the membrane. In this study, well‐established pH‐responsive and cross‐linked polymeric vesicles are studied. A pH‐controllable and stable membrane, as well as a hollow particle shape and membrane uniformity are confirmed using dynamic light scattering (DLS) and cryogenic‐transmission electron microscopy (Cryo‐TEM). Post‐loading with myoglobin (Mb) as a model enzyme is analyzed using multidetector asymmetrical flow field‐flow fractionation (AF4). Advanced analysis of conformational parameters allowed for the estimation of enzyme localization and the pH‐dependent loading efficiency thereof. Static light scattering coupled to AF4 is employed to successfully deliver information on the global size of the polymersomes (>50 nm). Furthermore, membrane structure and thickness, which are in the few nanometer range, can be successfully analyzed using small‐angle neutron scattering (SANS). Deuterated solvent as well as Mb deuteration for tuning the contrast are considered. Two different vesicle model fits, as well as Kratky–Porod interpretation confirm effective determination of vesicle core and membrane thickness and for evaluation of the membrane changes after post‐loading. [ABSTRACT FROM AUTHOR]

Asymmetrical flow field‐flow fractionation is a rising useful technique to separate and characterize macromolecules. Elution behaviors of allergen protein ovalbumin and immunoglobulin E were studied here. Effects of flow rates, kinds of carrier solutions, and injection amounts were investigated in the desire to experiment and verify the effect of every factor and to validate asymmetrical flow field‐flow fractionation theory. Results suggested that cross‐flow is the most important factor among all the factors that have been studied. Too‐low focus flow (0.5 ml/min) and outflow (0.4 ml/min) are harmful for protein separation and characterization. Smaller size ovalbumin (with a monomer is 11.4 nm) is more prone to be influenced compared with the bigger analyte immunoglobulin E (with a monomer diameter is 32.1 nm) by flow rates. The adopted types of carrier fluids did not change the retention behavior of the two proteins. Still, protein aggregation and membrane adsorption should be paid more attention to under different carrier fluids. [ABSTRACT FROM AUTHOR]

Iron (Fe) colloids dominate the soil solution Fe and these colloids potentially act as vectors for nutrients and contaminants in soil. The question remains which factors, that is, gradients in soil chemical characteristics with depth or physical processes, cause vertical mobilisation and immobilisation of Fe colloids in soils. This question was addressed by characterising the change in concentration, size and composition of Fe colloids in a podzol profile and by relating these changes to soil properties along the profile. Pore waters were analysed with Flow Field Flow Fractionation (FlFFF‐UV‐ICP‐MS) to overcome the artefacts typically obtained when using filtration for fractionation. Pore water was obtained by centrifugation of field moist samples taken from an Albic Podzol. The samples were taken within a depth of 110 cm, at eight depths corresponding to different horizons. The pore water Fe concentration increased with depth and peaked at 66 μM in the E horizon just above the Bh horizon, beyond which, it sharply decreased to only 9 μM. The pore water Fe concentration correlated strongly with dissolved organic carbon (DOC). The high‐resolution size fractionation analysis with FlFFF suggested that the Fe colloids (<100 nm) in the pore water not only consisted of Fe‐organic carbon (OC) complexes, but also of mineral Fe colloids associated with organic matter (OM), as indicated by the colloid size (>5 nm) and by the relatively large Fe/OC ratio that exceeds the complexation capacity of natural OM. The smallest mineral Fe colloids dominated in the Ah1 horizon, while the larger mineral colloids increased with increasing depth, explaining the rise in total Fe towards the Bh horizon. This suggests that Fe complexation with OM and stabilisation of mineral Fe colloids with OM explain colloidal Fe in the pore water. The adsorption of the OM at the top of the Bs horizons is likely the primary mechanism of DOC retention in the Bh horizon. Below this depth, the concentration of DOC was very low, resulting in low Fe concentration in the pore water. The colloids (<100 nm) are considerably smaller than the soil pore size distribution and increase in size with depth, which suggests that straining was not a significant mechanism for colloid retention. This study demonstrates that OM plays a key role in the transport of Fe colloids in acid sandy soil. Highlights: Depth profile of pore water Fe in a podzol is studied to investigate colloid migration processesPore water colloids are characterised by Flow Field Flow FractionationFe colloids consist of complexes with OM and mainly larger mineral colloidsNatural OM plays a key role in the transport of Fe colloids in acid sandy soil [ABSTRACT FROM AUTHOR]

Biodegradable polymer nano‐ and microparticles are of interest as drug carriers due to their capability to modulate drug release. Two different methods, including solvent displacement and spray drying, are used, resulting in the fabrication of Artemisone (ART)‐loaded polymeric nano‐ and microparticles, respectively. Scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and asymmetric flow field flow fractionation (AF4) are employed to evaluate the morphology and size of the particles. The encapsulation and loading efficiency of the drug as well as cumulative release are characterized using high‐performance liquid chromatography (HPLC). HPLC results confirm that the spray drying method provides higher encapsulation efficiencies of about 97%, whereas, in nanoparticles prepared by solvent displacement, the highest encapsulation efficiency is 71%. Using these production methods, round‐shaped particles with homogeneous size distribution are fabricated. Moreover, the preparation procedure is optimized to obtain particles with the highest encapsulation and drug loading efficiency. Using the solvent displacement method, stable dispersions in water are obtained without adding any surfactant, whereas, for spray‐dried microparticles, tween 80 is needed to redisperse particles. The micro‐ and nanoparticles show different release properties, which are of interest for drug delivery application of hydrophobic drugs like ART. [ABSTRACT FROM AUTHOR]

This review presents field‐flow fractionation: The elements of theory enable the link between the retention and the characteristics of the nanometer‐sized analytes to be highlighted. In particular, the nature of force and its way of being applied are discussed. Four types of forces which determine four types of techniques were considered: hydrodynamic, sedimentation, thermal, and electrical; this is to show the importance of the choice of technique in relation to the characterization objectives. Then the separation performance is presented and compared with other separation techniques: field‐flow fractionation has the greatest intrinsic separation capability. The characterization strategies are presented and discussed; on the one hand with respect to the characteristics needed for the description of nanoparticles; on the other hand in connection with the choice of the nature of the force, and also of the detectors used, online or offline. The discussion is based on a selection of published study examples. Finally, current needs and challenges are addressed, and as response, trends and possible characterization solutions. [ABSTRACT FROM AUTHOR]

Iron (Fe)‐rich colloids in the environment have a high surface reactivity and facilitate transport of oxyanions and trace metal cations in soil. This study was set up to help identify the soil properties that might affect the concentrations of colloidal Fe and its size distribution in pore waters of soils. The pore water was isolated by centrifugation from a collection of 97 topsoils with contrasting properties and land use. The total Fe concentration in the pore waters ranged between 0.2 and 26 μM (10th–90th percentile) and was largest at low soil solution calcium (Ca) and high dissolved organic carbon (DOC), indicating that enhanced colloidal stability determines total Fe in solution. The colloidal size distribution (<100 nm) of Fe in the pore waters of 11 soils was determined with flow field flow fractionation (FlFFF‐UV‐ICP‐MS), which yielded three different fractions that varied strikingly among soils. The smallest fraction (<5 nm) of Fe co‐eluted with high DOC and copper (Cu), suggesting mononuclear Fe‐organic carbon (OC) complexes. This fraction increased with an increasing DOC/Fe ratio in pore waters. The 5–50‐nm fraction of Fe prevailed in soils with >3.5% organic carbon (%OC), whereas the 50–100‐nm fraction was dominant in soils with low %OC content. This suggests that natural organic matter inhibits crystallization and growth of mineral Fe particles. The elemental ratios of mineral colloids (>5 nm) indicated the presence of clay minerals and Fe oxyhydroxides, which was confirmed by scanning electron microscopy (SEM) analysis. This study thus identified soil %OC and Ca in soil solution as the dominant factors predicting both the concentration and size of pore water Fe colloids, with the smallest and, potentially, most mobile Fe colloids occurring in OC‐rich soils. Highlights: Pore water iron concentrations in topsoils are governed by colloid stabilityFlow field flow fractionation analysis allows characterization of iron colloids in the low nanometre rangeIron colloid size and composition vary strikingly among soilsSmall iron colloids prevail in organic carbon‐rich soils due to colloid growth inhibition [ABSTRACT FROM AUTHOR]

Different colloidal particle characterization methods are examined for their suitability to determine the particle size distribution of particles extracted from steels. Microalloyed steels are dissolved to extract niobium and titanium carbonitride particles that are important for the mechanical properties of these steels. Such particles have sizes ranging from several nanometers to hundreds of nanometers depending on the precipitation stage during the thermomechanically controlled rolling process. The size distribution of the particles is analyzed by dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and hollow fiber flow field‐flow fractionation (HF5) and compared to data obtained for reference particles as well as data from electron microscopy, the standard sizing technique used in metallurgy today. AUC and HF5 provide high‐quality size distributions, average over large particle numbers that enables statistical analysis, and yield useful insights for alloy design; however, DLS fails due to a lack of resolution. Important aspects in the conversion and comparison of size distributions obtained for broadly distributed particle systems with different measurement principles and the role of surfactants used in sample preparation are discussed. [ABSTRACT FROM AUTHOR]

The measurement of physicochemical properties of polydisperse complex biological samples, for example, extracellular vesicles, is critical to assess their quality, for example, resulting from their production and isolation methods. The community is gradually becoming aware of the need to combine multiple orthogonal techniques to perform a robust characterization of complex biological samples. Three pillars of critical quality attribute characterization of EVs are sizing, concentration measurement and phenotyping. The repeatable measurement of vesicle concentration is one of the key‐challenges that requires further efforts, in order to obtain comparable results by using different techniques and assure reproducibility. In this study, the performance of measuring the concentration of particles in the size range of 50–300 nm with complementary techniques is thoroughly investigated in a step‐by step approach of incremental complexity. The six applied techniques include multi‐angle dynamic light scattering (MADLS), asymmetric flow field flow fractionation coupled with multi‐angle light scattering (AF4‐MALS), centrifugal liquid sedimentation (CLS), nanoparticle tracking analysis (NTA), tunable resistive pulse sensing (TRPS), and high‐sensitivity nano flow cytometry (nFCM). To achieve comparability, monomodal samples and complex polystyrene mixtures were used as particles of metrological interest, in order to check the suitability of each technique in the size and concentration range of interest, and to develop reliable post‐processing data protocols for the analysis. Subsequent complexity was introduced by testing liposomes as validation of the developed approaches with a known sample of physicochemical properties closer to EVs. Finally, the vesicles in EV containing plasma samples were analysed with all the tested techniques. The results presented here aim to shed some light into the requirements for the complex characterization of biological samples, as this is a critical need for quality assurance by the EV and regulatory community. Such efforts go with the view to contribute to both, set‐up reproducible and reliable characterization protocols, and comply with the Minimal Information for Studies of Extracellular Vesicles (MISEV) requirements. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) exists ubiquitously in the aquatic environment with varying chemical compositions and a wide molecular weight (MW) distribution, which, as a result, exhibits differing impacts on the behavior and fate of contaminants. The current methods for the MW characterization of DOM usually possess some weaknesses and therefore, some novel techniques are needed. In this study, the feasibility and sensitivity of flow field‐flow fractionation (FlFFF) system were studied for the MW characterization of DOMs from various origins. The systematic evaluation of FlFFF indicated that a mobile phase consisting of 10 mM NaCl and 5 mM H3BO3 and with a pH of 8 was optimal, and the fractionation program with a cross‐flow rate of 2 mL/min and a focusing time of 2 min resulted in the most efficient MW fractionation. Compared to natural waters, the standard DOM materials possessed a high proportion of humic‐like substances and narrow MW distribution. The quantification analysis showed that chromophoric organic ligands were mainly distributed in the high (i.e., 100 kDa–0.45 μm) and low (i.e., 0.3–1 kDa) MW fractions for natural waters, but in the medium (i.e., 1–100 kDa) and low MW fractions for the standard DOM materials. However, the fluorescent humic‐like substances were predominantly distributed within the medium and low MW fractions, irrespective of DOM types. This study showed the feasibility and sensibility of FlFFF in fractionating DOM samples, and can be used to quantify the different MW distribution of chromophoric and fluorescent components in standard and natural DOM. [ABSTRACT FROM AUTHOR]

The widespread application of nanoparticles (NPs) in recent times has caused concern because of their effects in biological systems. Although NPs can be produced naturally, industrially synthesized NPs affect the metabolism of a given organism because of their high reactivity. The biotransformation of NPs involves different processes, including aggregation/agglomeration, and reactions with biomolecules that will be reflected in their toxicity. Several analytical techniques, including inductively coupled plasma mass spectrometry (ICP‐MS), have been used for characterizing and quantifying NPs in biological samples. In fact, in addition to providing information regarding the morphology and concentration of NPs, ICP‐MS‐based platforms, such as liquid chromatography/ICP‐MS, single‐particle ICP‐MS, field‐flow fractionation (asymmetrical flow field‐flow fractionation)‐ICP‐MS, and laser ablation‐ICP‐MS, yield elemental information about molecules. Furthermore, such information together with speciation analysis enlarges our understanding of the interaction between NPs and biological organisms. This study reports the contribution of ICP‐MS‐based platforms as a tool for evaluating NPs in distinct biological samples by providing an additional understanding of the behavior of NPs and their toxicity in these organisms. [ABSTRACT FROM AUTHOR]

The batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying. [ABSTRACT FROM AUTHOR]

Size exclusion chromatography (SEC) for the molar mass analysis of polymers is of limited use for the analysis of branched polymers due to the co‐elution of linear and branched molecules with similar hydrodynamic sizes but different molar masses. Thermal field‐flow fractionation (ThFFF) in combination with multiple detection methods is a versatile alternative to SEC due to the fact that fractionation is not based entirely on molecular size but the interplay of thermal and translational diffusion that depend on molecular topology and molecular size. Multidetector ThFFF is used to investigate the correlation of branching and molar mass by determining polymer conformations from Mark–Houwink plots and the degrees of branching using functionality plots. The suitability of this approach is demonstrated for a set of 3‐, 4‐, and 6‐arm star polystyrenes as well as a more complex hyperbranched polybutadiene‐polystyrene copolymer. It is shown that ThFFF is a powerful tool for the analysis of the radius of gyration and the hydrodynamic radius when coupled online to static light scattering, viscometry, and dynamic light scattering. Shape factors are evaluated as influenced by branching where narrow dispersed star polystyrenes are used as model systems for the analysis of the more complex hyperbranched polybutadiene–polystyrene copolymer. [ABSTRACT FROM AUTHOR]

Sunlight consists of beams of light of broad wavelength ranges, including infrared, visible, and ultraviolet (UV) radiation; X‐rays; and γ‐rays. Although the UV content of sunlight is relatively low, the human body, especially the human skin, is sensitive to UV rays. Mica is known to be effective in protecting the human skin from sunlight and reduces fine lines and pores on the skin. Mica is currently used as a coloring agent in various sunscreen products. Still, there is no detailed report on the effect of mica on the sun protection factor (SPF). In this study, effects of the particle size, particle size distribution, and the content of mica on SPF were studied. Gravitational field‐flow fractionation (GrFFF) was employed to analyze the particle size and the particle size distribution of the mica particles. GrFFF provided size‐based separation of the mica particles and was useful for determining the size distributions and average sizes of the mica particles. It was found that the mixing ratio (in wt %) of 3:3:4 of TiO2:octyl methoxycinnamate:mica yielded the highest SPF. Generally, the SPF tends to increase with increasing particle size of the mica. [ABSTRACT FROM AUTHOR]

Electrical field flow fractionation (EFFF) is a particle separation method that employs an electrical field to cause particles in the carrier flow transferring in the vertical direction. The electrical characteristics of EFFF are one of the important aspects to explore electrical field how to work on the particle separation in EFFF channel. The equivalent electrical circuit model of EFFF channel was built. The experiments of chronoamperometry and electrochemical impedance spectroscopy (EIS) were conducted on the EFFF channel. The electrical circuit was utilised to fit the data of EIS experiments on EFFF channel. The fitting data were compared with the experimental data of EIS. The result indicates that the experimental data is highly quantified with the fitting data. It manifested that the equivalent electrical circuit reflected the electrical characteristics of the EFFF channel. [ABSTRACT FROM AUTHOR]

Thallium (Tl) is a trace element associated with base metal mining and processing, but little is known regarding how its toxicity is influenced by water chemistry. In the present study, the 48‐h median lethal concentration (LC50) of Tl to Daphnia magna was determined in a standard laboratory water, and toxicity was reassessed under conditions of varying cation (Ca2+, K+, Na+), anion (Cl–, HCO–3), and dissolved organic matter (DOM) concentrations. The calculated 48‐h LC50 of 1.86 mg Tl/L was consistent with previous work on Tl toxicity to D. magna. At the 48‐h LC50 concentration, changes in water chemistry had no statistically significant effect on mortality, although there was a trend toward lower Tl toxicity with elevated water K+. Test waters containing 10 mM CaCl2 did not support control survival. The measurement of Tl complexation with DOM using asymmetric flow field flow fractionation confirmed the outcomes of biogeochemical speciation modeling: Tl speciation was relatively unaffected by water chemistry, and the majority of Tl remained in the ionic form across all treatments. These data indicate that Tl toxicity is largely independent of speciation, a property that will greatly simplify risk assessments for this metal in freshwaters. Environ Toxicol Chem 2019;38:2472–2479. © 2019 SETAC [ABSTRACT FROM AUTHOR]

The foundation of separation science is the division or deconvolution of a mixture into constituent parts. To do so greatly informs our understanding of complex systems. Equally important is consideration of the behavior of a mixture as a whole—to consider if the whole is the sum of the parts or if individual components interact synergistically or antagonistically when combined. Application of separation science has seldom assumed greater importance than in consideration of the controversy surrounding the traditional and emergent views of the complex chemical system of natural organic matter (NOM). Analyses of simulated and actual environmental water samples using noninvasive separation techniques including flow field‐flow fractionation (flow FFF), excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analyses, and dynamic light scattering (DLS) are discussed. The data are used to explore whether a distinct chemical category of humic (diagenetic) substances exists in NOM; whether separation of organic matter into fulvic and humic extracts has relevant meaning translatable to actual environmental water samples; whether extraction procedures alter the chemistry of NOM extracts; and, if humic and fulvic acids exist, what physicochemical property or properties make humic substances unique among other forms of NOM. A fluorescence‐based nonoperational definition of humic substances is introduced. The underexplored role of supramolecular, self‐assembled aggregation is presented as a NOM conceptual model. Responses are provided to questions raised in the great NOM debate within a supramolecular context. Core Ideas: A new supramolecular conceptual model invokes strong near‐covalent hydrogen bonding.A nonoperational definition of diagenetic (humic) substances is proposed.Alkali extracts are valid, though imperfect, organic matter proxies.A mechanism for intrinsic chemical recalcitrance of natural organic matter exists.Protection is a "function" of the supramolecular "form." [ABSTRACT FROM AUTHOR]

Several postdepositional processes impact snow nitrate; however, only the isotopic effects of nitrate photolysis have been quantified. Here we discuss results from experiments in field Antarctic snow investigating isotopic fractionation of nitrate due to volatilization. At −35 °C, concentration and isotopic composition of nitrate remained constant during the 16‐day experiment. At −24 °C, 7.5% of nitrate was lost, synchronous with 1.5‰ decrease in δ18O and a constant δ15N. At −4 °C, 38% of nitrate was lost, and δ15N and δ18O decreased by 3.1 and 1.8‰, respectively. Results at −4 °C yield calculated fractionation constants close to theoretical estimates including equilibrium isotopic exchange between nitric acid and nitrate and the desorption of nitric acid from water in quasi‐liquid layers. This suggests that isotopic fractionation associated with nitrate volatilization across most of Antarctica, especially at sites with temperatures <−24 °C, should be minor, but the isotopic effects at warmer sites should be considered in interpreting archived nitrate records. Plain Language Summary: In polar regions, there is great interest in using nitrate archived in snow/ice to reconstruct aspects of atmospheric composition and the influence of natural versus man‐made emissions. However, nitrate can be lost from the snowpack, such that the archived signals do not directly reflect atmospheric loading. Stable isotopes of nitrate in snow/ice allow for tracking and understanding the origins of nitrate and how it might have changed after deposition. While the isotopic fractionation associated with photolytic loss of nitrate has been directly quantified, that of volatilization remains poorly understood. Thus, we completed field experiments in Antarctica to investigate the isotopic effects of nitrate volatilization from snow. Results show that nitrate volatilization loss is significant at −4 °C, resulting in an important change (depletion of heavy isotopes) in both nitrogen and oxygen in remaining snow nitrate. This can be largely explained by a combination of equilibrium isotopic exchange between nitric acid and nitrate and the desorption of nitric acid from water in ice surface layers. At lower temperatures (<−24 °C), nitrate loss is rather minor, and the isotopic fractionation is found to be negligible. The findings suggest that the isotopic effects of NO3− volatilization in snow are closely related to temperature. Key Points: Field experiments in Antarctica (over 16 days) were used to quantify the isotopic effects of NO3− volatilization from snowVolatilization at −4 °C depletes heavy isotopes of NO3− in remaining snow versus relatively constant isotopic ratios observed at −35 °CVolatilization can decrease δ15N in remaining snow NO3− in warm regions by several per mil, contrary to isotopic effects of photolysis [ABSTRACT FROM AUTHOR]

Sulfur Mass‐Independent Fractionation (S‐MIF) may provide a clue to understanding Earth's early atmosphere. We examined total pressure dependence of the S‐MIF produced by SO2 photolysis. Isotopic self‐shielding is known to produce S‐MIF, which could be changed by both the partial pressure of SO2 (pSO2) and by the total pressure (pTotal). Our experimental results show that both Δ33S and Δ36S values are constant when total pressure is below 10 kPa at constant pSO2, whereas they decrease as total pressure increases. The result suggests that pressure broadening of the SO2 absorption line is responsible for the S‐MIF. The modeled high‐resolution isotopologue cross sections can reproduce our experimental results and its changes depending on both pSO2 and pTotal. Consequently, we conclude that the Archean Δ33S and Δ36S correlation can only be achieved when the total pressure of the Archean atmosphere was below 100 kPa, or it was produced in the upper atmosphere. Plain Language Summary: Sulfur Mass‐Independent Fractionation (S‐MIF) in Archean sedimentary rocks could be useful to constrain the chemical and physical states of Earth's early atmosphere. SO2 photolysis is known to produce large MIF. However, experimental results have yet to model the observed mechanisms of S‐MIF in SO2 photolysis. We examined the total pressure effect of S‐MIF by SO2 photolysis and succeeded in modeling the observed S‐MIF and its total pressure dependence. Comparing the results of this study with geological records, large Archean S‐MIF could only be achieved when total pressure is below 100 kPa, suggesting that the Archean atmosphere was not thicker than the modern atmosphere or that the S‐MIF‐yielding photolysis occurred mainly at a high altitude. Key Points: Total pressure effect of sulfur mass‐independent fractionation during SO2 photolysis was examinedThe observed total pressure dependence can be explained by self‐shielding with pressure broadening of the SO2 absorption lineBased on the results, the large Archean Δ36S/Δ33S fractionations can only be achieved when total pressure was lower than 100 kPa [ABSTRACT FROM AUTHOR]

Purpose: Intensity‐modulated radiation therapy (IMRT) has allowed optimization of three‐dimensional spatial radiation dose distributions permitting target coverage while reducing normal tissue toxicity. However, radiation‐induced normal tissue toxicity is a major contributor to patients’ quality of life and often a dose‐limiting factor in the definitive treatment of cancer with radiation therapy. We propose the next logical step in the evolution of IMRT using canonical radiobiological principles, optimizing the temporal dimension through which radiation therapy is delivered to further reduce radiation‐induced toxicity by increased time for normal tissue recovery. We term this novel treatment planning strategy “temporally feathered radiation therapy” (TFRT). Methods: Temporally feathered radiotherapy plans were generated as a composite of five simulated treatment plans each with altered constraints on particular hypothetical organs at risk (OARs) to be delivered sequentially. For each of these TFRT plans, OARs chosen for feathering receive higher doses while the remaining OARs receive lower doses than the standard fractional dose delivered in a conventional fractionated IMRT plan. Each TFRT plan is delivered a specific weekday, which in effect leads to a higher dose once weekly followed by four lower fractional doses to each temporally feathered OAR. We compared normal tissue toxicity between TFRT and conventional fractionated IMRT plans by using a dynamical mathematical model to describe radiation‐induced tissue damage and repair over time. Results: Model‐based simulations of TFRT demonstrated potential for reduced normal tissue toxicity compared to conventionally planned IMRT. The sequencing of high and low fractional doses delivered to OARs by TFRT plans suggested increased normal tissue recovery, and hence less overall radiation‐induced toxicity, despite higher total doses delivered to OARs compared to conventional fractionated IMRT plans. The magnitude of toxicity reduction by TFRT planning was found to depend on the corresponding standard fractional dose of IMRT and organ‐specific recovery rate of sublethal radiation‐induced damage. Conclusions: TFRT is a novel technique for treatment planning and optimization of therapeutic radiotherapy that considers the nonlinear aspects of normal tissue repair to optimize toxicity profiles. Model‐based simulations of TFRT to carefully conceptualized clinical cases have demonstrated potential for radiation‐induced toxicity reduction in a previously described dynamical model of normal tissue complication probability (NTCP). [ABSTRACT FROM AUTHOR]

To accurately characterize branched polysaccharides with high molecular weights from medicinal and edible mushrooms and identify the limitations of size exclusion chromatography, molecular characteristics of polysaccharides from Tremella fuciformis were determined and compared by asymmetrical flow field-flow fractionation coupled with multiangle laser light scattering and refractive index detection, and size exclusion chromatography coupled with multiangle laser light scattering and refractive index detection, respectively. Results showed that molecular weights of three batches of T. fuciformis polysaccharides were determined as 2.167 × 106 (TF1), 2.334 × 106 (TF2), and 2.435 × 106 Da (TF3) by size exclusion chromatography, and 3.432 × 106 (TF1), 3.739 × 106 (TF2), and 3.742 × 106 Da (TF3) by asymmetrical flow field-flow fractionation, as well as 3.469 × 106 Da (TF1) by off-line multiangle laser light scattering, respectively. Results suggested that size exclusion chromatography was unable to accurately characterize T. fuciformis polysaccharides, which may be due to its limitations such as shear degradation and abnormal coelution. Compared to size exclusion chromatography, asymmetrical flow field-flow fractionation could be a better technique for the molecular characterization of branched polysaccharides with high molecular weights from medicinal and edible mushrooms, as well as from other natural resources. [ABSTRACT FROM AUTHOR]

In this study, a dielectrophoresis field-flow fractionation device was analyzed using a numerical simulation method and the behaviors of a set of different cells were investigated. By reducing the alternating current frequency of the electrodes from the value used in the original setup configuration and increasing the number of exit channels, total discrimination in cell trajectories and subsequent separation of four cell types were achieved. Cells were differentiated based on their size and dielectric response that are represented in their real part of Clausius-Mossotti factor at different frequencies. A number of novel designs were also proposed based on the original setup configuration. It was seen that by reducing the length of the main channel and the number of electrodes at low frequencies and not changing the inlet flow velocities, cell separation was still achieved successfully, although with a slightly larger electrode voltage. The shorter main channel decreased the residence time for the cells on the chip and also reduced the overall size of the device-these were improvements over the original design. The obtained results can be used to analyze other cell types by knowing their size and dielectric properties to design geometries that can ensure separation. [ABSTRACT FROM AUTHOR]

ABSTRACT Herein, we report the formation of α-amylase containing polyelectrolyte complexes (PECs). The method for the encapsulation of α-amylase is based on interactions between two oppositely charged polyelectrolytes, poly(acrylic acid) (PAA) and polyethylenimine (PEI). We could show that electrostatic interactions ensure the incorporation of the enzyme into the formed polyelectrolyte complexes. The encapsulation has no negative effect on enzyme activity and protects against denaturation of the enzyme initiated by low pH values. The resulting PECs are 150-250 nm in size with narrow size distribution, appear in a spherical shape and are colloidally stable. The complexation of both polyelectrolytes and the immobilization of α-amylase are investigated using fractionating techniques mainly the analytical ultracentrifugation and asymmetrical-flow field-flow fractionation. The formation of PECs represents a simple method for the encapsulation of α-amylase without the use of organic solvents and requires no additional purifications steps. This one-step approach, yielding high encapsulation efficiencies, shows the potential as a drug delivery system for sensitive hydrophilic actives in future. α-amylase is immobilized in polyelectrolyte complexes made of polyethylenimine and poly(acrylic acid). Optimized encapsulation conditions and the resulting polyelectrolyte complexes are investigated via determination of IEP, α-amylase activity assays, nanoDSC measurements, zeta potential values, dynamic light scattering, microscopy, and fractionating techniques. The encapsulated enzyme is protected against denaturation initiated by low pH values. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45036. [ABSTRACT FROM AUTHOR]

The ability of block copolymers to self-assemble into various nanostructures (such as micelles) has attracted significant attention over the years as these block copolymers provide a versatile platform that can readily be modified for a wide range of applications. As such, the solution behaviour of block copolymers has been at the forefront of the modern nanotechnology revolution. However, these novel block copolymer-based self-assemblies lack suitable characterisation techniques to determine size, molar mass and compositional distributions simultaneously. This mini-review gives a short background on the current techniques used to determine important micelle properties as well as their limitations for characterising complex samples. Current column-based fractionation techniques used for determining property distributions are addressed. As a result of the limitations of column-based fractionations, a multidetector thermal field-flow fractionation ( ThFFF) approach is put forward as a powerful alternative for determining not only size and molar mass distributions, but also other micelle properties as a function of temperature. More importantly, ThFFF is highlighted as the only current characterisation platform capable of addressing the analytical challenges associated with compositional distributions of polymer self-assemblies. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

An energy-efficient crude distillation unit (CDU) was proposed, and its performance was evaluated and compared with that of a conventional CDU. The problem of the large energy demand associated with the single-column operation of a conventional CDU was solved with a two-column operation - a prefactionator and a main column - in the proposed CDU. The two-column operation reduces feed-tray mixing, and thus raises the thermodynamic efficiency of the CDU. The proposed unit has reduced heating and cooling duty compared with that of the conventional unit. The proposed unit also has fewer investment and utility costs. Vapor and liquid flow connections between the two columns are readily available by adjusting the difference in column operating pressure. [ABSTRACT FROM AUTHOR]

The development of floating liquefied natural gas (FLNG) plants has resulted in a focus on reducing the weight and size of the topside processing facilities for these units. The conventional fractionation of natural gas liquids (NGL) in LNG plants implies a direct sequence of three or more conventional distillation columns requiring different levels of refrigeration. The results of a feasibility study are described, indicating that a packed three-product dividing-wall column (DWC) could replace conventional de-ethanizer and depropanizer columns. This could provide significant energy, hardware, weight, and footprint benefits, but, very likely, at the expense of an unaffordable cold utilities demand.1) [ABSTRACT FROM AUTHOR]

Families of amphiphilic oxidation-responsive polymers (poly(ethylene glycol)-polysulfides) with different architectures (linear, 4, 6, and 8-armed stars and 10, 15, and 20-armed combs) and compositions (variable ethylene sulfide/propylene sulfide ratio) are prepared. In water, all the polymers assemble in spherical micelles, with critical micellar concentrations <0.01 mg mL−1 for all the branched polymers. Triple-detection gel permeation chromatography (GPC) and asymmetric field flow fractionation (AFFF) with dynamic and static light scattering detection, respectively, show an increasing compaction of the polymeric coil and a strong reduction of the aggregation number with increasing degree of branching. The key finding of this study is that the kinetics of the oxidative response sharply depend on the branching; in particular, it is highlighted that the degree of branching influences the lag time before a response can be observed rather than the speed of the response itself, a phenomenon that is attributed to a branching-dependent solubility of the oxidant in the polysulfide matrix. [ABSTRACT FROM AUTHOR]

Silica nanoparticles were synthesized by emulsion polymerization by mixing ethanol, ammonium hydroxide, water, and tetraethyl orthosilicate. An apparatus was designed and assembled for a large-scale synthesis of silica nanospheres, which was aimed for uniform mixing of the reactants. Then sedimentation field-flow fractionation ( SdFFF) was used to determin the size distribution of the silica nanoparticles. SdFFF provided mass-based separation where the retention time increased with the particle size, thus the size distribution of silica nanoparticles obtained from SdFFF appeared more accurate than that from dynamic light scattering, particularly for those having broad and multimodal size distributions. A disk-shaped porous carbon membrane ( PCM) was manufactured for application as an adsorbent by pressurizing the silica particles, followed by calcination. Results showed that PCM manufactured in this study has relatively high surface area and temperature stability. The PCM surface was modified by attaching a carboxyl group ( PCM-COOH) and then by incorporating silver ( PCM-COOH-Ag). The amount of COOH group on PCM was measured electrochemically by cyclic voltammetry, and the surface area, pore size, pore volume of PCM-COOH-Ag by Brunauer-Emmet-Teller measurement. The surface area was 40.65 and reduced to 13.02 after loading a COOH group then increased up to 30.37 after incorporating Ag. [ABSTRACT FROM AUTHOR]

Rapid development of chromatographic processes relies on effective high-throughput screening (HTS) methods. This article describes the development of pseudo-linear gradient elution for resin selectivity screening using RoboColumns®. It gives guidelines for the implementation of this HTS method on a Tecan Freedom EVO® robotic platform, addressing fundamental aspects of scale down and liquid handling. The creation of a flexible script for buffer preparation and column operation plus efficient data processing provided the basis for this work. Based on the concept of discretization, linear gradient elution was transformed into multistep gradients. The impact of column size, flow rate, multistep gradient design, and fractionation scheme on separation efficiency was systematically investigated, using a ternary model protein mixture. We identified key parameters and defined optimal settings for effective column performance. For proof of concept, we examined the selectivity of several cation exchange resins using various buffer conditions. The final protocol enabled a clear differentiation of resin selectivity on miniature chromatography column (MCC) scale. Distinct differences in separation behavior of individual resins and the influence of buffer conditions could be demonstrated. Results obtained with the robotic platform were representative and consistent with data generated on a conventional chromatography system. A study on antibody monomer/high molecular weight separation comparing MCC and lab scale under higher loading conditions provided evidence of the applicability of the miniaturized approach to practically relevant feedstocks with challenging separation tasks as well as of the predictive quality for larger scale. A comparison of varying degrees of robotic method complexity with corresponding effort (analysis time and labware consumption) and output quality highlights tradeoffs to select a method appropriate for a given separation challenge or analytical constraints. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1503-1519, 2016 [ABSTRACT FROM AUTHOR]

This study outlines the synthetic and purification process used to obtain hyperbranched polyglycerol (HPG) within a molecular weight range not previously obtainable. Purified fractions with low polydispersity are achieved via successive precipitations from acetone. Furthermore, the use of the initiator molecule 5-hexyne-1-ol introduces alkyne functionality at the core of each HPG molecule. Alkyne-azide cycloaddition chemistry in combination with NMR and field flow fractionation analysis is used to verify the availability of the alkyne core for bioconjugation across the range of molecular weights. [ABSTRACT FROM AUTHOR]

A number of methods are available to researchers for estimating molecular weights (molar masses) and molecular weight distributions of starches − or those in solution, using an appropriate solvent/solubilisation protocol. We outline the methods available and assess their relative merits and limitations. We focus on size-exclusion chromatography or field flow fractionation coupled to multi-angle light scattering, viscometry, and sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge. [ABSTRACT FROM AUTHOR]

We present the development of a dynamic model for predicting the trajectory of microparticles in microfluidic devices, employing dielectrophoresis, for Hyperlayer field-flow fractionation. The electrode configuration is such that multiple finite-sized electrodes are located on the top and bottom walls of the microchannel; the electrodes on the walls are aligned with each other. The electric potential inside the microchannel is described using the Laplace equation while the microparticles' trajectory is described using equations based on Newton's second law. All equations are solved using finite difference method. The equations of motion account for forces including inertia, buoyancy, drag, gravity, virtual mass, and dielectrophoresis. The model is used for parametric study; the geometric parameters analyzed include microparticle radius, microchannel depth, and electrode/spacing lengths while volumetric flow rate and actuation voltage are the two operating parameters considered in the study. The trajectory of microparticles is composed of transient and steady state phases; the trajectory is influenced by all parameters. Microparticle radius and volumetric flow rate, above the threshold, do not influence the steady state levitation height; microparticle levitation is not possible below the threshold of the volumetric flow rate. Microchannel depth, electrode/spacing lengths, and actuation voltage influence the steady-state levitation height. [ABSTRACT FROM AUTHOR]

The high morbidity and mortality rate of bloodstream infections involving antibiotic-resistant bacteria necessitate a rapid identification of the infectious organism and its resistance profile. Traditional methods based on culturing the blood typically require at least 24 h, and genetic amplification by PCR in the presence of blood components has been problematic. The rapid separation of bacteria from blood would facilitate their genetic identification by PCR or other methods so that the proper antibiotic regimen can quickly be selected for the septic patient. Microfluidic systems that separate bacteria from whole blood have been developed, but these are designed to process only microliter quantities of whole blood or only highly diluted blood. However, symptoms of clinical blood infections can be manifest with bacterial burdens perhaps as low as 10 CFU/mL, and thus milliliter quantities of blood must be processed to collect enough bacteria for reliable genetic analysis. This review considers the advantages and shortcomings of various methods to separate bacteria from blood, with emphasis on techniques that can be done in less than 10 min on milliliter-quantities of whole blood. These techniques include filtration, screening, centrifugation, sedimentation, hydrodynamic focusing, chemical capture on surfaces or beads, field-flow fractionation, and dielectrophoresis. Techniques with the most promise include screening, sedimentation, and magnetic bead capture, as they allow large quantities of blood to be processed quickly. Some microfluidic techniques can be scaled up. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:823-839, 2016 [ABSTRACT FROM AUTHOR]

A universal technique has been proposed to sort two-dimensional (2D) sub-nanometer thin crystals (manganese dioxide MnO2 and molybdenum disulfide MoS2) according to their lateral dimensions. This technique is based on tuning the zeta potential of their aqueous dispersions which induces the selective sedimentation of large-sized 2D crystals and leaves the small-sized counterparts in suspension. The electrocatalytic properties of as-obtained 2D ultrathin crystals are strongly dependent on their lateral size. As a proof-of-concept study, the small-sized MnO2 nanocrystals were tested as the electrocatalysts for the urea-oxidation reaction (UOR), which showed outstanding performance in both half reaction and full electrolytic cell. A mechanism study reveals the enhanced performance is associated with the remarkable structural properties of MnO2 including ultrathin (ca. 0.95 nm), laterally small-sized (50-200 nm), and highly exposed active centers. [ABSTRACT FROM AUTHOR]

Particle size is one of the important parameters that determine the characteristics (and applicability) of silica nanoparticles. An accurate sizing technique is therefore required for quality control during the synthesis of silica nanoparticles. Unlike other sizing techniques, the field-flow fractionation ( FFF) provides size-based separation of colloidal particles, and allows an FFF elution profile, which can be converted to a size distribution directly. Synthesis of silica nanoparticles having narrow size distributions is not trivial, as there are many parameters affecting the characteristics of the synthesized particles. In this study, silica nanoparticles were synthesized by emulsion polymerization, where ethanol, ammonium hydroxide, and tetraethyl orthosilicate ( TEOS) were mixed at room temperature. First, silica nanoparticles were synthesized in a smaller scale with a total reaction volume of 175 mL. Then the effect of various reaction parameters on the particle size distribution ( PSD) was systematically investigated using asymmetrical flow FFF ( AF4), a member of FFF family. The synthesis scale was then increased to the total reaction volume of 3 L. It was observed that, as the concentrations of TEOS and ethanol increased, the size of the silica nanoparticles tended to decrease, while as the concentration of ammonium hydroxide increased, the size tended to increase. Silica nanoparticles of about 100 nm having a relatively narrow size distribution could be obtained in a large scale with the concentrations of TEOS, ethanol, and ammonia solution of 95, 95, and 15%, respectively. The results suggest that AF4 is a useful tool for fast and accurate size monitoring of silica nanoparticles. [ABSTRACT FROM AUTHOR]

Due to the limited solubility of phosphorus (P) in soil, understanding its binding in fine colloids is vital to better forecast P dynamics and losses in agricultural systems. We hypothesized that water-dispersible P is present as nanoparticles and that iron (Fe) plays a crucial role for P binding to these nanoparticles. To test this, we isolated water-dispersible fine colloids (WDFC) from an arable topsoil (Haplic Luvisol, Germany) and assessed colloidal P forms after asymmetric flow field-flow fractionation coupled with ultraviolet and an inductively coupled plasma mass spectrometer, with and without removal of amorphous and crystalline Fe oxides using oxalate and dithionite, respectively. We found that fine colloidal P was present in two dominant sizes: (i) in associations of organic matter and amorphous Fe (Al) oxides in nanoparticles <20 nm, and (ii) in aggregates of fine clay, organic matter and Fe oxides (more crystalline Fe oxides) with a mean diameter of 170 to 225 nm. Solution 31P-nuclear magnetic resonance spectra indicated that the organically bound P predominantly comprised orthophosphate-monoesters. Approximately 65% of P in the WDFC was liberated after the removal of Fe oxides (especially amorphous Fe oxides). The remaining P was bound to larger-sized WDFC particles and Fe bearing phyllosilicate minerals. Intriguingly, the removal of Fe by dithionite resulted in a disaggregation of the nanoparticles, evident in higher portions of organically bound P in the <20 nm nanoparticle fraction, and a widening of size distribution pattern in larger-sized WDFC fraction. We conclude that the crystalline Fe oxides contributed to soil P sequestration by (i) acting as cementing agents contributing to soil fine colloid aggregation, and (ii) binding not only inorganic but also organic P in larger soil WDFC particles. [ABSTRACT FROM AUTHOR]

Asymmetric flow field-flow fractionation (AF4) is an analytical separation technique capable of providing information on different parameters of complex systems in a single measurement. Although it shows promise to be an important tool in the field of gene therapy, AF4 has only occasionally been used to study gene delivery vectors such as polyplexes. Here, AF4 is applied to investigate novel vector systems based on hybrid polymer-magnetic micelles, magnetopolyplexes. These are multicomponent systems, composed of small magnetic nanoparticles loaded in cationic block copolymer micelles that are complexed with DNA; they exhibit enhanced transfection efficiency in the presence of a magnetic field. It is demonstrated that the application of AF4 to these systems provides complementary information related to the fractionation of the samples, the disintegration of the vectors, the presence of fractions of small particles, unbound micelles, and DNA, and the composition of the magnetopolyplexes, which can hardly be obtained by conventional methods. [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]

In this study, multidetector Thermal FFF (ThF3) is utilized to study amphiphilic block copolymers in different selective and nonselective solvents. Depending on the solvent quality and the polymer concentration, amphiphilic block copolymers can form aggregates or micelles; the blocks can adopt different coil conformations. ThF3 is chosen because of the noninvasive nature of the technique that will not destroy the conformations that amphiphilic block copolymers can adopt in selected solvents. The effect of different polymer-solvent systems on the diffusion and thermal diffusion coefficients, and the resultant separation, is studied. It is found that, depending on the solvent, the macromolecules adopt extended coil or partially collapsed coil conformations. Experimental conditions are identified where the block copolymers behave similar to one of their parent homopolymers. For the first time, it has been shown that ThF3 is a unique tool to study the solution properties and the coil conformations of amphiphilic copolymers and to relate this information to the fractionation behavior of the polymers. [ABSTRACT FROM AUTHOR]

ABSTRACT Diblock copolymers of poly[2-(dimethylamino)ethyl methacrylate]- block-poly[di(ethylene glycol) methyl ether methacrylate], PDMAEMA- b-PDEGMA, were synthesized by reversible addition-fragmentation chain transfer polymerization. The block ratio was varied to study the influence on the lower critical solution temperature and the corresponding phase transition in water. Therefore, turbidimetry, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and laser Doppler velocimetry were applied. Additionally, asymmetric flow field-flow fractionation (AF4) coupled to DLS and multiangle laser light scattering (MALLS) was established as an alternative route to characterize these systems in terms of molar mass of the polymer chain and size of the colloids after the phase transition. It was found that AF4-MALLS allowed accurate determination of molar masses in the studied range. Nevertheless, some limitations were observed, which were critically discussed. The cloud point and phase transition of all materials, as revealed by turbidimetry, could be confirmed by DSC. For block copolymers with block ratios in the range of 50:50, a thermo-induced self-assembly into micellar and vesicular structures with hydrodynamic radii ( Rh) of around 25 nm was observed upon heating. At higher temperatures, a reordering of the self-assembled structures could be detected. The thermo-responsive behavior was further investigated in dependence of pH value and ionic strength. Variation of the pH value mainly influences the solubility of the PDMAEMA segment, where a decrease of the pH value increases the transition temperature. An increase of ionic strength leads to a reduction of the cloud point due to the screening of electrostatic interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 924-935 [ABSTRACT FROM AUTHOR]

In this study, a stability-indicating reversed-phase liquid chromatographic electrospray mass spectrometric method was developed and validated for the determination of process-related impurities and forced degradants of Efavirenz in bulk drugs. Efavirenz was subjected to acid, alkaline hydrolysis, H2O2 oxidation, photolysis, and thermal stress. Significant degradation was observed during alkaline hydrolysis, and the degradants were isolated on a mass-based purification system and characterized by high-resolution mass spectrometry, positive electrospray ionization tandem mass spectrometry, and 1H and 13C NMR spectroscopy. Accurate mass measurement and NMR spectroscopy revealed the possible structure of process-related impurities and degradant under stress conditions. The acceptable separation was accomplished on Waters bondapak C18 column (250 mm × 4.6 mm; 5 μm), using 5 mM ammonium acetate and acetonitrile as a mobile phase in a gradient elution mode at a flow rate of 1.0 mL/min. The eluents were monitored by diode array detector at 247 nm and quantitation limits were obtained in the range of 0.1-2.5 μg/mL for Efavirenz, degradants, and process-related impurities. The liquid chromatography method was validated with respect to accuracy, precision, linearity, robustness, and limits of detection and quantification as per International Conference on Harmonization guidelines. [ABSTRACT FROM AUTHOR]

The study is primarily focused on the possibility to utilize organic asymmetric flow field-flow fractionation (A4F) coupled to a multi-angle light scattering (MALS) detector for the characterization of copolymers of methyl methacrylate with various acrylates prepared by emulsion polymerization. The effects of acrylate monomer type and content on the molar mass distribution and degree of branching of acrylic copolymers have been studied by A4F-MALS using tetrahydrofuran as a carrier solvent. It has been found that the growing amount of acrylate results in the increase of molar mass, polydispersity, and branching degree as a result of chain transfer to polymer. Highly branched compact macromolecules with ultra-high molar mass were identified in all copolymers containing a high level of acrylate. In contrast to size traditionally used exclusion chromatography, organic A4F-MALS has been proved as a very efficient technique for the characterization of high molar mass acrylic emulsion copolymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40995. [ABSTRACT FROM AUTHOR]

We investigated theoretically the effects of the cross-stream migration and the local average orientation of rodlike particles on the shape-based separation using field-flow fractionation. The separation behavior was analyzed by comparing the retention ratios of spheres and rods. The retention ratio of a rod was evaluated through the derivation of its cross-sectional concentration profile by considering the rod migration and the local average orientation. Our study in various flow conditions showed that the rod migration, caused by the hydrodynamic interaction with a wall, can affect the separation behavior as a lift-hyperlayer mode. We also demonstrated that the local average orientation, which is a function of a local shear rate and a rotational diffusivity, results in the transverse diffusivity that is different from its perpendicular diffusivity. These results suggest that the experimental separation behaviors of rods in field-flow fractionation may not be fully explained by the current theory based on the normal mode and the steric mode. We also characterized each condition where one of the normal mode, the steric mode of spheres, and the lift-hyperlayer mode of rods is dominant. [ABSTRACT FROM AUTHOR]

Rigid particles transported through a pinched-flow fractionation (PFF) device are simulated using boundary-integral methods (BIM). The PFF device separates particles by size using a bifurcated microfluidic channel. The critical flow ratio of the two input channels required to achieve complete separation of large and small particles decreases with increasing diameter of the larger particles relative to the pinch height, and is nearly independent of the smaller particle size. A narrow pinch with a square exit was shown to have the lowest critical flow ratio and was selected as the model device to be fabricated. Experiments conducted using this device confirm that the larger particles exit further from the top wall than do the smaller particles, due to steric exclusion, and the final exit positions are within a few percent of the simulation results. It is shown that BIM is a valuable tool in the design of microfluidic devices. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3444-3457, 2013 [ABSTRACT FROM AUTHOR]