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Due to the increased applications of engineered elemental metal nanoparticles (EMNPs) in recent years, increased attention has been devoted to their release into the environment. EMNPs pose potenti...

The efficiency of a frit inlet asymmetrical flow field‐flow fractionation (FI‐AFlFFF) channel has been evaluated by varying the length of the inlet frit element. In a FI‐AFlFFF channel, a high speed frit flow is introduced through the inlet frit to provide hydrodynamic relaxation of the incoming sample stream from the channel inlet. The experimental plate heights and peak recovery values are examined for three different FI‐AFlFFF channels by varying field strengths and the channel membrane materials. It has been found that the length of the inlet frit element influences the performance of hydrodynamic relaxation, as well as peak recovery in the FI‐AFlFFF channel system. Experimental plate height data show that the hydrodynamic relaxation itself occurs more efficiently when the length of inlet frit is longer. While an FI‐AFlFFF channel having a longer inlet frit (4.2 cm long) gives a good relaxation, it shows less efficiency in considering peak recovery over a range of the field strengths examined...

Two different sample relaxation methods (focusing relaxation and hydrodynamic relaxation) in asymmetrical flow field-flow fractionation (AFlFFF) are examined by using a conventional asymmetrical channel and a frit inlet asymmetrical channel. In this report, sample recovery using a protein standard is studied, comparing focusing relaxation and hydrodynamic relaxation process at various field strengths and outflow rate conditions. It is shown that a conventional AFlFFF channel provides a better resolution than a frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) channel, with sample recoveries up to 80% under moderate field strength conditions. Focusing relaxation appears to provide flexibility in selecting high speed run conditions without losing resolution, since sample relaxation is expected to be achieved more completely than hydrodynamic relaxation. The FI-AFlFFF channel utilizing the hydrodynamic relaxation provides a relatively poor resolution and separation speed; however, it performs...

Flow/hyperlayer field flow fractionation (Fl/Hy FFF) has been applied for the rapid separation and size characterization of core-shell type poly(l-lactide) (PLLA) microspheres which are widely studied as a potential drug carrier due to its biodegradability. Examined microspheres are prepared by varying the entrapped amount of the retinoic acid as an anti-cancer therapeutic and varying PEG-PLLA copolymers. It is demonstrated that the separation of PLLA microspheres can be achieved within 5 min. by Fl/Hy FFF and the particle size distribution (PSD) is readily obtained from the experimental fractograms. From the size distribution of PLLA particles obtained by Fl/Fl FFF, it is shown that PSD increases with the amount of drug loaded but it does not seriously change with the addition of PEG-PLLA copolymers.

The frit inlet asymmetrical flow field-flow fractionation is applied to the separation of proteins by using a stopless flow injection procedure. By utilizing a small permeable frit near the injection point in an asymmetrical flow FFF channel, sample materials injected to the flow streams can be hydrodynamically relaxed by the compressing action of high speed frit flow and the focusing/relaxation procedure can be bypassed. The separation efficiency of the frit inlet asymmetrical flow FFF channel is demonstrated with few protein standards by examining the influence of the ratio of injection flow rate to frit flow rate on the band broadening during relaxation.

Sedimentation Field-Flow Fractionation (SdFFF) has been applied to the size characterization of nonspherical, rod shaped chromium dioxide particles which are currently being used as magnetic recording media. Retention of the rod shaped particles in SdFFF was largely dependent on flow rates and external field strengths. To obtain an accurate size distribution profile, a proper run condition was chosen at which retention of rods follows the SdFFF theory. While retention of rods at a high field strength was decreased by the role of lift forces, it was shown that retention at a low field strength was increased by the restricted diffusion of rod like particles. At an optimum run condition, where no retention perturbations existed, an apparent diameter distribution of rods was easily obtained, and then converted to a length distribution with the application of the average cross-section diameter of rod shaped chromium dioxide particles measured by microscopy.

Sedimentation/steric field-flow fractionation (Sd/StFFF) is an elution separation technique capable of measuring the size distribution of 0.3–100 µm spherical and near-spherical particles with advantages including high resolution, fast analysis, and the ready collection of narrow size fractions. In this study we investigate the applicability of Sd/StFFF to various nonspherical particles including the doublets of spheres, rod-shaped glass fibers, compressed latex discs, and quartz particles (BCR 67 and 70) with complex mixed shapes. Some fractionation, retention, and selectivity features of these particles are defined and measured in relationship to those of spheres (latex beads), which are better understood. While the relative behavior of these two particle types depends on many factors, especially the distance of the particle from the Sd/StFFF channel wall, in most cases the nonspherical particles are eluted before spheres of equal volume and they often display higher selectivity than spherical ...