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Separations
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Field-Flow Fractionation
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Field-Flow Fractionation

A special issue of Separations (ISSN 2297-8739).

Deadline for manuscript submissions: closed (31 July 2015) | Viewed by 47674

Special Issue Editor

Dr. Ronald Beckett

E-Mail Website1 Website2
Guest Editor
School of Chemistry, Monash University, Caulfield East, VIC, Australia
Interests: separation science; field-flow fractionation including hyphenated techniques; aquatic science; colloid and surface chemistry; humic substances; aquatic and soil particles; pollutant transport and speciation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Field-flow fractionation (FFF) is an established separation and characterization method suitable for macromolecules and particles in the diameter range 1 nm–50 nm. FFF is an elution method analogous to liquid chromatography and can separate samples into fractions that can be collected for further analysis or, alternatively, it can be hyphenated to other detectors such as ICPMS, light scattering, fluorescence, etc. The elution time can be used to provide size, molecular weight and other physical characteristics of the sample either using well established theory or calibration. FFF has been used on a wide variety of samples including polymers, proteins, humic substances, aquatic and soil particles, biological cells and synthetic nanoparticles.

This Special Issue aims to present readers with the latest research regarding FFF. The issue invites contributions relating to all aspects of FFF including theory developments, instrumentation and applications.

Dr Ron Beckett
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Separations is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Keywords

  • field-flow fractionation
  • FFF
  • macromolecules
  • colloids
  • nanoparticles
  • particles
  • separation
  • characterization
  • applications
  • theory

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Published Papers (7 papers)

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Research

1096 KiB  
Article
Hyphenation of Field-Flow Fractionation and Magnetic Particle Spectroscopy
by Norbert Löwa, Patricia Radon, Dirk Gutkelch, Rinaldo August and Frank Wiekhorst
Chromatography 2015, 2(4), 655-668; https://doi.org/10.3390/chromatography2040655 - 25 Nov 2015
Cited by 11 | Viewed by 6258
Abstract
Magnetic nanoparticles (MNPs) exhibit unique magnetic properties making them ideally suited for a variety of biomedical applications. Depending on the desired magnetic effect, MNPs must meet special magnetic requirements which are mainly determined by their structural properties (e.g., size distribution). The hyphenation of [...] Read more.
Magnetic nanoparticles (MNPs) exhibit unique magnetic properties making them ideally suited for a variety of biomedical applications. Depending on the desired magnetic effect, MNPs must meet special magnetic requirements which are mainly determined by their structural properties (e.g., size distribution). The hyphenation of chromatographic separation techniques with complementary detectors is capable of providing multidimensional information of submicron particles. Although various methods have already been combined for this approach, so far, no detector for the online magnetic analysis was used. Magnetic particle spectroscopy (MPS) has been proven a straightforward technique for specific quantification and characterization of MNPs. It combines high sensitivity with high temporal resolution; both of these are prerequisites for a successful hyphenation with chromatographic separation. We demonstrate the capability of MPS to specifically detect and characterize MNPs under usually applied asymmetric flow field-flow fractionation (A4F) conditions (flow rates, MNP concentration, different MNP types). To this end MPS has been successfully integrated into an A4F multidetector platform including dynamic ligth scattering (DLS), multi-angle light scattering (MALS) and ultraviolet (UV) detection. Our system allows for rapid and comprehensive characterization of typical MNP samples for the systematic investigation of structure-dependent magnetic properties. This has been demonstrated by magnetic analysis of the commercial magnetic resonance imaging (MRI) contrast agent Ferucarbotran (FER) during hydrodynamic A4F fractionation. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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1214 KiB  
Article
Particle Based Modeling of Electrical Field Flow Fractionation Systems
by Tonguc O. Tasci, William P. Johnson, Diego P. Fernandez, Eliana Manangon and Bruce K. Gale
Chromatography 2015, 2(4), 594-610; https://doi.org/10.3390/chromatography2040594 - 9 Oct 2015
Cited by 5 | Viewed by 7487
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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1393 KiB  
Article
Conductivity-Dependent Flow Field-Flow Fractionation of Fulvic and Humic Acid Aggregates
by Martha J. M. Wells
Chromatography 2015, 2(3), 580-593; https://doi.org/10.3390/chromatography2030580 - 22 Sep 2015
Cited by 11 | Viewed by 5960
Abstract
Fulvic (FAs) and humic acids (HAs) are chemically fascinating. In water, they have a strong propensity to aggregate, but this research reveals that tendency is regulated by ionic strength. In the environment, conductivity extremes occur naturally—freshwater to seawater—warranting consideration at low and high [...] Read more.
Fulvic (FAs) and humic acids (HAs) are chemically fascinating. In water, they have a strong propensity to aggregate, but this research reveals that tendency is regulated by ionic strength. In the environment, conductivity extremes occur naturally—freshwater to seawater—warranting consideration at low and high values. The flow field flow fractionation (flow FFF) of FAs and HAs is observed to be concentration dependent in low ionic strength solutions whereas the corresponding flow FFF fractograms in high ionic strength solutions are concentration independent. Dynamic light scattering (DLS) also reveals insight into the conductivity-dependent behavior of humic substances (HSs). Four particle size ranges for FAs and humic acid aggregates are examined: (1) <10 nm; (2) 10 nm–6 µm; (3) 6–100 µm; and (4) >100 µm. Representative components of the different size ranges are observed to dynamically coexist in solution. The character of the various aggregates observed—such as random-extended-coiled macromolecules, hydrogels, supramolecular, and micellar—as influenced by electrolytic conductivity, is discussed. The disaggregation/aggregation of HSs is proposed to be a dynamic equilibrium process for which the rate of aggregate formation is controlled by the electrolytic conductivity of the solution. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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1853 KiB  
Article
Synthetic Smectite Colloids: Characterization of Nanoparticles after Co-Precipitation in the Presence of Lanthanides and Tetravalent Elements (Zr, Th)
by Muriel Bouby, Nicolas Finck and Horst Geckeis
Chromatography 2015, 2(3), 545-566; https://doi.org/10.3390/chromatography2030545 - 1 Sep 2015
Cited by 2 | Viewed by 6504
Abstract
The magnesian smectite hectorite is a corrosion product frequently detected in nuclear waste glass alteration experiments. The structural incorporation of a single trivalent lanthanide was previously demonstrated. Hectorite was presently synthesized, for the first time, in the presence of several lanthanides (La, Eu, [...] Read more.
The magnesian smectite hectorite is a corrosion product frequently detected in nuclear waste glass alteration experiments. The structural incorporation of a single trivalent lanthanide was previously demonstrated. Hectorite was presently synthesized, for the first time, in the presence of several lanthanides (La, Eu, Yb) following a multi-step synthesis protocol. The smallest-sized particles (nanoparticles, NPs) were isolated by centrifugation and analyzed by asymmetrical flow field-flow fractionation (AsFlFFF) coupled to ICP-MS, in order to obtain information on the elemental composition and distribution as a function of the size. Nanoparticles can be separated from the bulk smectite phase. The particles are able to accommodate even the larger-sized lanthanides such as La, however, with lower efficiency. We, therefore, assume that the incorporation proceeds by substitution for octahedral Mg accompanied by a concomitant lattice strain that increases with the size of the lanthanides. The presence of a mixture does not seem to affect the incorporation extent of any specific element. Furthermore, syntheses were performed where in addition the tetravalent zirconium or thorium elements were admixed, as this oxidation state may prevail for many actinide ions in a nuclear waste repository. The results show that they can be incorporated as well. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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2131 KiB  
Article
An Improved Model for the Steric-Entropic Effect on the Retention of Rod-like Particles in Field-Flow Fractionation: Discussion of Aspect Ratio-Based Separation
by Joontaek Park and Anand Mittal
Chromatography 2015, 2(3), 472-487; https://doi.org/10.3390/chromatography2030472 - 28 Jul 2015
Cited by 8 | Viewed by 6421
Abstract
We developed an improved model for predicting the steric-entropic effect on the separation behaviors of rod-like particles in flow field-flow fractionation. Our new model incorporates the “pole-vault” rotation of a rod-like particle near a wall under shear flow into the original model developed [...] Read more.
We developed an improved model for predicting the steric-entropic effect on the separation behaviors of rod-like particles in flow field-flow fractionation. Our new model incorporates the “pole-vault” rotation of a rod-like particle near a wall under shear flow into the original model developed by Beckett and Giddings which considered only Brownian rotation. We investigated the effect of the aspect ratio on the retention ratios and the cross-sectional concentration distribution in the separation of rods in field-flow fractionation (FFF). Our analyses involved comparing the results predicted using the original model and those from the new model under various rod geometries and flow conditions. We found that the new model can show the aspect ratio-enhanced elution trend in certain flow conditions for the assumption of non-constant cloud thickness (ratio between the cross flow rate and the rod diffusivity). We also deducted that the flow conditions allowing for the aspect ratio-enhanced elution are related to the interplay among the axial flow rate, cloud thickness, and rod geometry. The new model can be viewed as a prototype to qualitatively show the aspect ratio-enhanced trend since its quantitative agreement with the experimental data must be improved for our future work. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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2342 KiB  
Communication
Fractionation and Characterization of High Aspect Ratio Gold Nanorods Using Asymmetric-Flow Field Flow Fractionation and Single Particle Inductively Coupled Plasma Mass Spectrometry
by Thao M. Nguyen, Jingyu Liu and Vincent A. Hackley
Chromatography 2015, 2(3), 422-435; https://doi.org/10.3390/chromatography2030422 - 14 Jul 2015
Cited by 12 | Viewed by 7270
Abstract
Gold nanorods (GNRs) are of particular interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared. Purified GNRs are essential for the advancement of technologies based on these materials. Used in concert, asymmetric-flow field [...] Read more.
Gold nanorods (GNRs) are of particular interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared. Purified GNRs are essential for the advancement of technologies based on these materials. Used in concert, asymmetric-flow field flow fractionation (A4F) and single particle inductively coupled mass spectrometry (spICP-MS) provide unique advantages for fractionating and analyzing the typically complex mixtures produced by common synthetic procedures. A4F fractions collected at specific elution times were analyzed off-line by spICP-MS. The individual particle masses were obtained by conversion of the ICP-MS pulse intensity for each detected particle event, using a defined calibration procedure. Size distributions were then derived by transforming particle mass to length assuming a fixed diameter. The resulting particle lengths correlated closely with ex situ transmission electron microscopy. In contrast to our previously reported observations on the fractionation of low-aspect ratio (AR) GNRs (AR < 4), under optimal A4F separation conditions the results for high-AR GNRs of fixed diameter (≈20 nm) suggest normal, rather than steric, mode elution (i.e., shorter rods with lower AR generally elute first). The relatively narrow populations in late eluting fractions suggest the method can be used to collect and analyze specific length fractions; it is feasible that A4F could be appropriately modified for industrial scale purification of GNRs. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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446 KiB  
Article
Adverse-Mode FFF: Multi-Force Ideal Retention Theory
by Tyler N. Shendruk and Gary W. Slater
Chromatography 2015, 2(3), 392-409; https://doi.org/10.3390/chromatography2030392 - 7 Jul 2015
Viewed by 6313
Abstract
A novel field-flow fractionation (FFF) technique, in which two opposing external forces act on the solute particles, is proposed. When the two external forces are sufficiently strong and scale differently as a function of the solutes’ property of interest (such as the solute [...] Read more.
A novel field-flow fractionation (FFF) technique, in which two opposing external forces act on the solute particles, is proposed. When the two external forces are sufficiently strong and scale differently as a function of the solutes’ property of interest (such as the solute particle size), a sharp peak in the retention ratio (dramatic drop in elution time) is predicted to exist. Because the external forces oppose one another, we refer to this novel technique as adverse-mode FFF. The location of this peak is theoretically predicted and its ideal width estimated. The peak can become quite sharp by simultaneously increasing the strength of both fields, suggesting that adverse-mode FFF could be a useful technique for accurately measuring single species solute size. Full article
(This article belongs to the Special Issue Field-Flow Fractionation)
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