Present situation and development trends of asymmetrical flow field-flow fractionation

Abstract

Field-flow fractionation (FFF) is a kind of mature separation technologies in the field of bioanalysis, feasible of separating analytes with the differences of certain physical and chemical properties by the combination effects of two orthogonal force fields (flow field and external force field). Asymmetrical flow field-flow fractionation (AF4) is a vital subvariant of FFF, which applying a vertical flow field as the second dimension force field. The separation in AF4 opening channel is carried out by any composition carrier fluid, universally and effectively used in separation of bioparticles and biopolymers due to the non-invasivity feature. Herein, bio-analytes are held in bio-friendly environment and easily sterilized without using degrading carrier fluid which is conducive to maintain natural conformation. In this review, FFF and AF4 principles are briefly described, and some classical and emerging applications and developments in the bioanalytical fields are concisely introduced and tabled. Also, special focus is given to the hyphenation of AF4 with highly specific, sensitive detection technologies.

Label-Free Isolation of Exosomes Using Microfluidic Technologies

“…Field flow fractionation (FFF) is a flow-based sorting method applicable for separation of particles ranging from a few nanometers to about 100 μm in diameter. − This technique has been widely utilized to isolate and characterize biological and nonbiological particles. − To separate particles, a liquid suspension containing particles traveling (laminar flow with a parabolic profile) in a narrow channel (height of 50–500 μm) while being subjected to an externally applied field (liquid flows, centrifugal forces, gravity or electrical fields) perpendicular to the direction of suspension flow (Figure A). − The separation mechanism is based on the differences in density and hydrodynamic properties of particles that define particle mobility under the effect of forces perpendicular to each other; the forward force exerted by laminar channel flow and vertical forces exerted by the externally applied field and diffusion. External field forces drive the accumulation of particles at the bottom wall of the channel, whereas Brownian motion of the particles results in their diffusion toward the channel center. − Depending on their equilibrium position from the wall of the microchannel, particles travel at different speeds and thereby are separated as they move down the microchannel (Figure A).…”

Characteristics of electrical field flow fractionation with chronoamperometry and electrochemical impedance

“…There are many subtechniques on FFF research, such as flow FFF (4F), electrical FFF (EFFF), thermal FFF (TFFF), sedimentation FFF (SFFF). The versatility of FFF had been demonstrated with numerous applications [11][12][13][14][15][16][17].…”