Abstract: A new field flow fractionation process for the separation of particles using a modified channel structure to achieve hydrodynamic relaxation without involving a stop-flow procedure and thus provide improved speed of operation as well as improved sample concentration, the new improved channel structure comprising a thin channel having one or more permeable wall sections contained in the enclosing wall or walls of the channel, the permeable wall sections making up not more than 25% of the total wall area of the channel, and adjustable flow control valves for controlling the flowrate of any fluid at the inlet end of the channel and independent flow control valves for controlling the flow rate of the fluid being introduced into or withdrawn from the permeable wall sections.

Abstract: A procedure for determining particle size and particle size distribution data from sedimentation field-flow fractionation comprises carrying out a calibration run in which a sample of particles of known density and size is injected into a liquid carrier stream flowing through a field-flow fractionation channel. The acceleration G acting on the calibration sample during the calibration run and the density difference .DELTA..rho. between the particles of the calibration sample and the liquid carrier of the calibration run are known. Retention time or retention volume of the particles of different known sizes are measured during the calibration run. The retention times or retention volumes are used to develop a calibration relationship expressing retention time or retention volume as a function of particle size. In a test run, a test sample of particles is injected into the liquid carrier stream flowing through the channel. The density difference .DELTA..rho.

Abstract: A continuous flow FFF process for the separation of samples of particles which uses a modified channel structure to reduce the relaxation effect, reduce sample adhesion to the wall, and where possible eliminate the stop-flow procedure and thus greatly increase the speed and stability of operation, said modified channel comprises a thin channel whose thickness is reduced at the inlet end for a substantial distance beyond the inlet, such as the conventional triangular or near triangular piece, and then broadened out at the outlet end of the channel.

Abstract: A process for continuous particle and polymer separation comprising injecting a stream of carrier fluid containing the material to be separated into the inlet end of a thin channel, adjusting the flow rate to a sufficiently high level that flow-dependent lift forces the different components to different transverse positions by the time they reach the end of the channel, splitting the outlet flow into at least two substreams by means of physical splitters, adjusting the flowrates of the multiple substreams such that the transverse position of the outlet splitting plane divides the particles into enriched fractions, collecting the enriched or separated components from the emerging outlet streams.

Abstract: A thin channel split flow process for particle fractionation which effects a rapid and efficient separation of the particles comprising continuously introducing two or more fluid substreams of different composition into separate inlet ports of a thin enclosed channel having a thickness which is very thin compared to the other two dimensions and bringing the substreams into contact with adjacent substreams so as to collectively form a series of thin laminae flowing parallel to one another in the channel and in contact with one another over a sufficient length of channel to allow a desired level of mass transport between and through laminae, continuously introducing a fluid medium containing the particles to be separated as one or more of the fluid substreams and independently of the particle concentration, varying the fluid composition of the different substreams as needed to realize separation, at the outlet end of the channel splitting the collective streams into another set of substreams so as to permit sep

Abstract: A process for high speed separation of ultra-high molecular weight polymers using a hyperlayer field-flow fractionation technique comprising forcing a carrier fluid containing a small sample of the high molecular weight polymer through a thin flow channel possessing an accumulation wall, applying a primary externally controlled driving force transversely across the thin dimension of the channel, adjusting the flowrate of the fluid and the field strength of the primary externally controlled force in relationship to the channel thickness such that at least over part of the molecular weight range the entropic force F.sub.e and the primary driving force F.sub.1 are related by the inequality .vertline.F.sub.e .vertline.>.vertline.F.sub.1 .vertline. at the accumulation wall of the channel.

Abstract: A thin channel split flow process for particle fractionation which effects a rapid and efficient separation of the particles comprising introducing a stream of fluid containing the particles to be separated into the inlet end of a thin enclosed channel whose transverse dimension is very small, applying a special field or gradient or combination thereof transversely across the thin dimension of the channel to create a driving force a component of which is perpendicular to the main flow plane, adjusting the flow rate to achieve laminar flow conditions throughout the channel to allow the particles under the influence of the field/gradient to segregate into different stream laminae as they approach different transverse equilibrium positions, splitting the channel stream at the outlet end into substreams containing different separated fractions of the particles in the initial mixture, recovering the substream and thereby recovering the separated fractions.

Abstract: A method and apparatus for continuous, steric field-flow fractionation and segregation of particles according to particle size. An elongate, fluid flow channel carrying a stream of entrained particles is subjected to a force field which urges the particles against one of the channel walls. The field strength is sufficient and in an appropriate direction to maintain the particles in close proximity to the wall so that particle size determines the rate of movement down the channel, the larger particles being exposed to the higher flow rates toward the center of the flow stream. The combined effects of fluid flow forces and force field strength develops a pattern of selective particle deflection from a point of particle infusion near the top of the channel, such that the particles drift and settle into segregated groups of common particle size.

Abstract: A steric field-flow fractionation system including a flow channel adapted for use with a carrier stream of fluid having particles suspended therein and a force field disposed across the flow channel to cause migration of the particles to a restraining wall, thereby forming layers of particles at the restraining wall. The strength of the force field is adjusted sufficiently high to maintain the particles of a given class at the restraining wall such that particle distance from the wall is a function of steric hindrance. Particle displacement by flow along the channel is thereby determined by particle size, permitting fractionation of the particles based on differential migration of the various sizes of particle classes.

Abstract: A method and apparatus for flow field-flow fractionation involving the application of a lateral cross flow superimposed on a channel fluid flow in a field-flow fractionation system. The cross flow is developed by applying a pressure across semipermeable plates which substantially define a narrow channel region carrying a fluid substance to be subjected to the influence of the cross flow. This cross flow causes differential migration of solute material carried by the channel flow, thereby providing application to numerous processes such as separations, fractionation, solute exchange, purification, dialysis and ultrafiltration.