SEARCH · PubMed Health

Results for “Fractionation, Field Flow”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed2005

Estimation of the particle-wall interaction energy in sedimentation field flow fractionation.

A new sedimentation field flow fractionation (SdFFF) method is presented for the estimation of the total potential energy of interaction between colloidal particles and the channel wall. The method is based on the variation of the mean cloud thickness in SdFFF due to the variation of the suspension's ionic strength. It requires only two SdFFF experiments at two different ionic strengths and at a constant acceleration field. The found values are compatible with those calculated from the various forms of equations of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.

Fractionation, Field Flow↗

PubMed2005

Size fractionation and characterization of natural colloids by flow-field flow fractionation coupled to multi-angle laser light scattering.

Flow-field flow fractionation (FlFFF) coupled to multi-angle laser light scattering (MALLS) was evaluated for size and shape determination of standard spherical and arbitrarily shaped natural colloids. Different fitting methods for light scattering data retrieved from MALLS were evaluated to determine the particle size of spherical standards and natural colloids. In addition, FlFFF was optimized for best fractionation in connection to MALLS, minimal colloids-membrane interaction, and minimal sample losses. FlFFF, calibrated with standard particles, was used to determine hydrodynamic diameter, or radius (D(h) or R(h)), of the fractionated colloids, whereas the MALLS was used to determine root mean square radius of gyration (R(g)) for fractionated colloids. Combining both results, by calculating the R(g)/R(h) ratio, allows an estimation of colloid deviation from the shape of homogeneous sphere. Accordingly, this study demonstrates that, FlFFF-MALLS is a valuable technique for characterizing heterogeneous and arbitrarily shaped natural colloidal particles in terms of size and shape. To check the usefulness of FlFFF-MALLS in natural colloid studies, the technique was used to investigate the sedimentation behavior of extracted soil colloidal particles. Results illustrate that, in a silty till sample, carbonates function as cement between the colloidal particles, and consequently, change their sedimentation behavior. On the other hand, carbonate dissolution generates a more homogeneous colloidal sample.

Colloids↗

PubMed1992

Elution mode of Pneumocystis carinii cysts in gravitational field-flow fractionation.

The simplest field-flow fractionation technique, i.e. gravitational, was used in an attempt to purify a Pneumocystis carinii cyst suspension. This parasite is an opportunistic invader in immunocompromised patients, especially those suffering from AIDS. The cyst stage is spherical and 5 microns in diameter. Unexpected retention times, not systematically related to the size and the density of the parasite, were obtained under various experimental conditions. When silicone-coated walls were used, Pneumocystis carinii cysts were eluted in the void volume, whereas when uncoated walls were used with a sodium dodecyl sulphate-enriched carrier phase, retention was observed. These phenomena are probably related to the high degree of hydrophobicity of these micrometre-sized biological particles; this degree can be easily determined. The use of the gravitational field-flow fractionation technique can be of a great interest for the development of new methods for diagnostic purposes. Particle-wall interactions and their modifications due to the carrier phase or to the wall treatment can be employed in the search for new bronchoalveolar lavage solutions.

Animals↗

PubMed2005

Geometric scaling effects on instrumental plate height in field flow fractionation.

This paper examines geometric scaling models for field flow fractionation systems to understand how channel dimensions affect resolution and retention. Specifically, the changing contribution of the instrumental plate height during miniaturization of field flow fractionation (FFF) systems is reported. The work is directed towards determining the optimal geometrical parameters for miniaturization of field flow fractionation systems. The experimental relationship between channel height in FFF systems and instrumental plate heights is reported. FFF scaling models are modified to: (i) better clarify the dependence of plate height and resolution on channel height in FFF and (ii) include a more complete geometrical scaling analysis and model comparison in the low retention regime. Electrical field flow fractionation has been shown to benefit from miniaturization, so this paper focuses on that subtype, but surprisingly, the results also indicate the possibility of improvement in performance with miniaturization of other field flow fractionation systems including general FFF subtypes in which the applied field does not vary with channel height. This paper also discusses the potential role of more powerful microscale field flow fractionation systems as a new class of sample preparation units for micro-total-analysis systems (mu-TAS).

Fractionation, Field Flow↗

PubMed2006

Fractionation of prion protein aggregates by asymmetrical flow field-flow fractionation.

Achieving the successful separation and analysis of amyloid and other large protein aggregates can be a difficult proposition. Field-flow fractionation (FFF) is a flow-based separation method like chromatography; however, FFF is capable of high-resolution separations in the absence of a stationary matrix. Thus, FFF is a relatively gentle technique and is well suited to the task of separating large macromolecules and macromolecular complexes. Flow field-flow fractionation (FlFFF), one of the techniques in the FFF family, has been used to successfully fractionate a wide size range of prion protein aggregates, allowing their subsequent characterization by several biophysical and biochemical methods. The ability to easily adjust the strength of the field used during separation means that FlFFF could be applied to particles ranging from 1 nm to nearly 100 mum in size. This flexibility, coupled with the ability to produce fast, high-resolution separations, makes FFF a potentially valuable tool in the field of amyloid research.

Chemical Fractionation↗

PubMed1989

Field-flow fractionation of macromolecules.

Field-flow fractionation (FFF) is a versatile family of techniques, applicable to macromolecules, colloids, and cell-sized particles. This paper focuses specifically on the applicability of FFF to macromolecules. Following a brief description of the principles of FFF, the characteristics of FFF that bear on its efficacy in separating macromolecules are summarized. The basis of selectivity is established. The general applicability of FFF to macromolecules is then surveyed. For this purpose macromolecular substances are divided into four classes, distinguished by a molecular weight cutoff of 10(6) and by aqueous versus organic solubility. The capabilities of different FFF subtechniques in fractionating these classes of macromolecules is then discussed.

Chemical Fractionation↗

PubMed1984

Sedimentation field flow fractionation of DNA's.

Sedimentation field flow fractionation (SFFF) is a method for purifying and providing mass or size distribution information on samples containing particulates or soluble macromolecules. Since SFFF separations are based on simple physical phenomena related to first principles, molecular weight (or particle sizes) can be determined without calibration standards. SFFF is a gentle technique suited for fractionating biomolecules. Studies with the fragile lambda DNA (molecular weight, 33 X 10(6] and smaller supercoiled plasmids have shown that these materials are not altered during SFFF separation; molecular weights and conformation remain unchanged, and biological activity is not reduced. Recoveries of nucleic acids approach 100 percent. Typically, components with about 20 percent difference in mass can be separated essentially to baseline if required. Fractionation time is usually independent of molecular weight, and separations often can be carried out within an hour.

Chemical Fractionation↗

PubMed2005

Hollow fiber flow field-flow fractionation of proteins using a microbore channel.

Protein separation through hollow fiber flow field-flow fractionation (HF FlFFF) at microflow rate regime was successfully achieved by employing a microbore hollow fiber. In most of the flow field-flow fractionation (FlFFF) techniques applied to the separation of proteins, including hollow fiber FlFFF (HF FlFFF), an outflow rate leading to a detector has typically been a few tenths of a milliliter per minute. In this study, it is demonstrated for the first time that 10 microL/min outflow rate in HF FlFFF can be employed for a successful separation of proteins by utilizing a small inner diameter (450 microm) hollow fiber. Initial evaluations of microbore HF FlFFF separation were made to improve separation efficiency by evaluating plate heights, sample recovery, and the limit of detection using protein standards. Microbore HF FlFFF was applied for the separation of low-abundance blood proteins depleted of high-abundance proteins from raw serum using immunoaffinity chromatography.

Fractionation, Field Flow↗

PubMed1994

Modification of glass channel walls for separation of biological particles by gravitational field-flow fractionation.

In the gravitational field-flow fractionation of complex samples, various interaction and adsorption phenomena can occur in separation channels that influence fractionation and complicate the explanation of resulting fractograms. To overcome these problems, the glass surface was modified to create charge-free, non-adsorbing hydrophilic media for the mild treatment of hydrophilic biological particles. The modification was carried out in two steps: (1) by a simple lacquering of the glass surface with polystyrene diluted in toluene and (2) subsequent adsorption of a detergent layer on polystyrene. Essential suppression of ionic interactions between soluble low-molecular-mass compounds and the channel wall and decreased adsorption effects were demonstrated in separations of blood samples by gravitational field-flow fractionation.

Adsorption↗

PubMed2004

Coupling gravitational and flow field-flow fractionation, and size-distribution analysis of whole yeast cells.

This work continues the project on field-flow fractionation characterisation of whole wine-making yeast cells reported in previous papers. When yeast cells are fractionated by gravitational field-flow fractionation and cell sizing of the collected fractions is achieved by the electrosensing zone technique (Coulter counter), it is shown that yeast cell retention depends on differences between physical indexes of yeast cells other than size. Scanning electron microscopy on collected fractions actually shows co-elution of yeast cells of different size and shape. Otherwise, the observed agreement between the particle size distribution analysis obtained by means of the Coulter counter and by flow field-flow fractionation, which employs a second mobile phase flow as applied field instead of Earth's gravity, indicates that yeast cell density can play a major role in the gravitational field-flow fractionation retention mechanism of yeast cells, in which flow field-flow fractionation retention is independent of particle density. Flow field-flow fractionation is then coupled off-line to gravitational field-flow fractionation for more accurate characterisation of the doubly-fractionated cells. Coupling gravitational and flow field-flow fractionation eventually furnishes more information on the multipolydispersity indexes of yeast cells, in particular on their shape and density polydispersity.

Cell Fractionation↗

PubMed1992

Analysis of Creutzfeldt-Jakob disease infectious fractions by gel permeation chromatography and sedimentation field flow fractionation.

Gel permeation chromatography and sedimentation field flow fractionation (SF3) were used to further analyze highly infectious fractions from Creutzfeldt-Jakob disease (CJD) infected hamster brain. These analyses defined the relative molecular mass and physical size of the Creutzfeldt-Jakob disease (CJD) agent with greater precision than previously possible. Highly purified disaggregated fractions yielded single, homogeneous Gaussian peaks with both methods. The relevant analytical peaks contained protein-nucleic acid complexes with an M(r) of approximately 1.5 x 10(7) daltons and a mean radius of approximately 30 nm. The experimental evidence further solidifies the concept of an infectious agent that resembles a viral core rather than a simple protein.

Animals↗

PubMed2004

Miniaturization of frit inlet asymmetrical flow field-flow fractionation.

A miniaturized frit inlet asymmetrical flow field-flow fractionation (mFI-AFlFFF) channel has been constructed and tested for the separation of proteins. By scaling down the geometrical channel dimension of a conventional FI-AFlFFF system, flow rate ranges that can be manipulated were decreased to 20-30 microL/min, which reduces the injection amount of sample materials. The end effect contribution to plate height was evaluated by varying the inner diameter of the connection tubing between the injector and the channel inlet at various injection flow rates, and the results showed that the use of silica capillary tubing of the shortest possible distance is essential in reducing the initial band broadening prior to the sample injection to the microscale channel. The capability of the microFI-AFlFFF system was demonstrated with the separation of protein standards, polystyrenesulfonates, and ssDNA strains and for the characterization of replication protein A-ssDNA binding complex regulated by redox status.

Alcohol Dehydrogenase↗

PubMed2000

Different elution modes and field programming in gravitational field-flow fractionation. 2. Experimental verification of the range of conditions for flow-rate and carrier liquid density programming.

Gravitational field-flow fractionation utilises the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating of particles from the channel accumulation wall. Therefore there are several possibilities to modulate the resulting force field acting on particles in gravitational field-flow fractionation. Regarding the force field programming in gravitational field-flow fractionation, this work focused on two topics: changes of the difference between particle density and carrier liquid density in Brownian and focusing elution modes and influencing of lift forces achieved by changing the flow-rate in focusing elution mode. We have found and described the experimental conditions applicable to force field programming in the case of separations of silica gel particles by gravitational field-flow fractionation. It was shown that the effect of carrier liquid viscosity in the water-methanol system is implemented as an additional factor enhancing the desired effect of carrier liquid density. Some other forces influencing the retention behaviour of the model particles are discussed.

Chemical Fractionation↗

PubMed2005

Predicting membrane flux decline from complex mixtures using flow-field flow fractionation measurements and semi-empirical theory.

Flow-Field Flow Fractionation (FI-FFF) is an idealization of the cross flow membrane filtration process in that, (1) the filtration flux and crossflow velocity are constant from beginning to end of the device, (2) the process is a relatively well-defined laminar-flow hydrodynamic condition, and (3) the solutes are introduced as a pulse-input that spreads due to interactions with each other and the membrane in the dilute-solution limit. We have investigated the potential for relating FI-FFF measurements to membrane fouling. An advection-dispersion transport model was used to provide 'ideal' (defined as spherical, non-interacting solutes) solute residence time distributions (RTDs) for comparison with 'real' RTDs obtained experimentally at different cross-field velocities and solution ionic strength. An RTD moment analysis based on a particle diameter probability density function was used to extract "effective" characteristic properties, rather than uniquely defined characteristics, of the standard solute mixture. A semi-empirical unsteady-state, flux decline model was developed that uses solute property parameters. Three modes of flux decline are included: (1) concentration polarization, (2) cake buildup, and (3) adsorption on/in pores, We have used this model to test the hypothesis-that an analysis of a residence time distribution using FI-FFF can describe 'effective' solute properties or indices that can be related to membrane flux decline in crossflow membrane filtration. Constant flux filtration studies included the changes of transport hydrodynamics (solvent flux to solute back diffusion (J/k) ratios), solution ionic strength, and feed water composition for filtration using a regenerated cellulose ultrafiltration membrane. Tests of the modeling hypothesis were compared with experimental results from the filtration measurements using several correction parameters based on the mean and variance of the solute RTDs. The corrections used to modify the boundary layer mass transfer coefficient and the specific resistance of cake or adsorption layers demonstrated that RTD analysis is potentially useful technique to describe colloid properties but requires improvements.

Adsorption↗

PubMed2004

The use of asymmetrical flow field-flow fractionation in pharmaceutics and biopharmaceutics.

Field-flow fractionation (FFF) is a family of flexible analytical fractionating techniques which have the advantage that the separation of analytes is achieved, solely through the interaction of the sample with an external, perpendicular physical field, rather than by the interaction with a stationary phase. The rapid progress in pharmaceutical biotechnology goes along with an increasing demand in potent, high-efficient analytical methods. Thus, FFF techniques are gaining increasing attention for their ability to separate and characterize populations of polymers, colloids and particles of up to about 100 microm in size. It is the intention of this review to provide an overview on common FFF techniques, to summarize inherent advantages and limitations and to introduce both established and challenging applications in the (bio)pharmaceutical field. Thereby, asymmetrical flow FFF is addressed predominantly, since it is the most versatile applicable FFF technique.

Biological Products↗

PubMed2005

Characterization of sewage plant hydrocolloids using asymmetrical flow field-flow fractionation and ICP-mass spectrometry.

Asymmetrical flow field-flow fractionation (AF4) was applied to characterize aquatic colloids from biological sewage plants and to infer information of colloidal loads, sources, and sinks within the plants, resp. the colloidal interaction with the aqueous phase and the sewage sludge. To characterize the colloids further, especially the distributions of colloid associated heavy metals, the AF4 system was coupled to an inductively coupled plasma mass spectrometer (ICP-MS). The size distribution is determined by AF4 with UV absorbance and fluorescence detection after a calibration by monodisperse polystyrene sulfonate standards (PSS). Samples from different sewage plants and from different depths and locations within a plant were compared. The fulvic/humic acid fraction with a particle diameter d(p) < 10 nm appeared to be comparable in all samples and decreases only slightly along the plants, whereas larger colloids with d(p) > 10 nm almost completely passed into the sewage sludge. The concentrations of the initial colloidal heavy metals decreased along the plants.

Colloids↗

PubMed2004

Separation of carbon nanotubes by frit inlet asymmetrical flow field-flow fractionation.

Flow field-flow fractionation (flow FFF), a separation technique for particles and macromolecules, has been used to separate carbon nanotubes (CNT). The carbon nanotube ropes that were purified from a raw carbon nanotube mixture by acidic reflux followed by cross-flow filtration using a hollow fiber module were cut into shorter lengths by sonication under a concentrated acid mixture. The cut carbon nanotubes were separated by using a modified flow FFF channel system, frit inlet asymmetrical flow FFF (FI AFIFFF) channel, which was useful in the continuous flow operation during injection and separation. Carbon nanotubes, before and after the cutting process, were clearly distinguished by their retention profiles. The narrow volume fractions of CNT collected during flow FFF runs were confirmed by field emission scanning electron microscopy and Raman spectroscopy. Experimentally, it was found that retention of carbon nanotubes in flow FFF was dependent on the use of surfactant for CNT dispersion and for the carrier solution in flow FFF. In this work, the use of flow FFF for the size differentiation of carbon nanotubes in the process of preparation or purification was demonstrated.

Journal Article↗

PubMed2005

Performance of hollow-fiber flow field-flow fractionation in protein separation.

Since hollow-fiber flow field-flow fractionation (HF FIFFF) utilizes a cylindrical channel made of a hollow-fiber membrane, which is inexpensive and simple in channel assembly and thus disposable, interests are increasing as a potential separation device in cells, proteins, and macromolecules. In this study, performance of HF FIFFF of proteins is described by examining the influence of flow rate conditions and length of fiber (polyacrylonitrile or PAN in this work) on sample recovery as well as experimental plate heights. The interfiber reproducibility in terms of separation time and recovery was also studied. Experiments showed that sample recovery was consistent regardless of the length of fiber when the effective field strength (equivalent to the mean flow velocity at the fiber wall) and the channel void time were adjusted to be equivalent for channels of various fiber lengths. This supported that the majority of sample loss in HF FIFFF separation of apoferritin and their aggregates may occur before the migration process. It is finally demonstrated that HF FIFFF can be applied for characterizing the reduction in Stokes' size of low density lipoproteins from blood plasma samples obtained from patients having coronary artery disease and from healthy donors.

Apoferritins↗