Asymmetrical flow field-flow fractionation as a method to study the behavior of humic acids in solution

Schimpf, Martin E.; Wahlund, Karl-Gustav

doi:10.1002/(sici)1520-667x(1997)9:7<535::aid-mcs3>3.0.co;2-2

Cited by 41 publications

(21 citation statements)

References 20 publications

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“…In AF4 setups where the particle radii are derived from the retention time according to the AF4 theory rather than from the MALS signal the observed shift in retention time would lead to significantly different particle size distributions. When varying the focus flow conditions within the chosen limits aggregation artifacts could not be observed in contrast to literature reports for other analytes [15]. For virus-like particles Chuan et al [16] found no aggregation sensitivity which is in accordance with our results.…”

supporting

confidence: 92%

“…In order to evaluate the total amount of particles eluting from the channel at different focus flow conditions the area under the curve (AUC) of the UV signal was calculated. The reduction in AUC which we observed is marginal (data not shown) and much less pronounced than that reported from other analytes, e.g., humic acid macromolecules [15]. Enhanced focus flow induced loss is generally regarded as an effect of adsorption to the accumulation wall due to enhanced interaction between analyte and membrane at higher focus flow.…”

Section: Influence Of Focus Flow Ratecontrasting

confidence: 70%

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Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

Hupfeld

Ausbacher

Brandl

2009

J of Separation Science

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Original Paper Asymmetric flow field-flow fractionation of liposomes: optimization of fractionation variablesThe purpose of this study was to investigate the influence of ionic strength of the carrier liquid, cross flow rate, focus flow rate, and sample load on the retention behavior of liposomes in asymmetric flow field-flow fractionation (AF4). Two differently prepared samples of large unilamellar vesicles (LUV) were used. Experiments were performed varying the factors systematically and evaluating their effect on both retention behavior of the liposomes and on particle size as obtained from online coupled multi-angle light scattering (MALS) analysis. The results showed that the focus flow rate had the least influence on the elution of liposomes. Elution of LUV is mainly governed by the chosen cross flow condition and ionic strength of the carrier liquid as well as its sample load. Optimal fractionation and size analysis were achieved using a sample load of about 10 lg, a cross flow gradient from 1.0 to 0.1 mL/min over 35 min and a carrier solution of NaNO 3 with a concentration of 10 mM. IntroductionLiposomes are vesicles consisting of an aqueous core surrounded by a phospholipid bilayer [1]. They have the ability to incorporate both amphiphilic and lipophilic compounds in their membrane-like bilayer as well as to encapsulate hydrophilic compounds [2]. Due to this ability liposomes have contributed to improving drug delivery of e.g., anthracyclines and play an important role in drug delivery research. It is widely accepted that liposomes as drug carriers may improve drug delivery in terms of therapeutic activity and safety [3 -5]. The size distribution of liposomes is important in terms of both the systemic circulation time upon injection into the blood stream and targeting abilities [3,6,7]. A study of the biodistribution of liposomes showed that the average size of the samples does not supply enough information and rather the size distribution should be used, especially for less homogeneous samples [7]. Asymmetric flow FFF (AF4) in combination with multi-angle light scattering (MALS) is the mostly applied sub-class of the FFF family and has gained increasing importance in the field of protein and peptide therapeutics as well as natural and synthetic polymers in recent years [8,9]. However, the number of publications about FFF of liposomes is rather limited compared to other applications and the technique has still not found widespread use despite it has various promising advantages over current particle size analysis methods such as photon correlation spectroscopy (PCS), and size exclusion chromatography [10,11]. For liposomal drug carriers a reliable size determination over the whole particle size spectrum from a few nanometers up to a micrometer could not be achieved with a single method so far. Such information on the other hand is essential for stringent control of the particle size which is governing the biodistribution and tumor targeting [7]. Despite a handful of successful attempts to characterize ...

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supporting

confidence: 92%

Section: Influence Of Focus Flow Ratecontrasting

confidence: 70%

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

Hupfeld

Ausbacher

Brandl

2009

J of Separation Science

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“…As pH of the carrier solution increases, the surfaces of PSS standards and natural DOM and the membrane may become more negatively charged, increasing the repulsion between sample analytes and the membrane. Thus, sample analytes could be distributed further away from the membrane and more toward the center of the channel where the laminar channel flow is faster, resulting in decreased retention time and decreased adsorption of colloids onto the membrane, and hence increased recovery [31,52,50]. Therefore, when the carrier solution was changed from Carrier 1 to 2, pH increased from 6 to 8, leading to higher recovery and earlier elution.…”

Section: Effect Of Carrier Solutions On Sample Recovery and Elution Timementioning

confidence: 99%

A critical evaluation of an asymmetrical flow field-flow fractionation system for colloidal size characterization of natural organic matter

Zhou

Guo

2015

Journal of Chromatography A

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“…This phenomenon could be explained by increased interactions between sample and membrane during focusing, the purpose of which is to concentrate the sample into a narrow zone prior to elution. It is known that concentration effects can lead to aggregation and interaction with the membrane at the accumulation wall (Schimpf and Wahlund, 1997). Better control over focusing conditions to allow for control of zone width, reduced concentration effects, and minimal sample interactions would be a significant improvement (Johann et al, 2011).…”

Section: Af4eri Data Analysis and Recoverymentioning

confidence: 99%

Amylose and amylopectin in starch by asymmetric flow field-flow fractionation with multi-angle light scattering and refractive index detection (AF4–MALS–RI)

Chiaramonte

Rhazi

Aussenac

et al. 2012

Journal of Cereal Science

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Asymmetrical flow field-flow fractionation as a method to study the behavior of humic acids in solution

Cited by 41 publications

References 20 publications

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

A critical evaluation of an asymmetrical flow field-flow fractionation system for colloidal size characterization of natural organic matter

Amylose and amylopectin in starch by asymmetric flow field-flow fractionation with multi-angle light scattering and refractive index detection (AF4–MALS–RI)

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