Sedimentation field-flow fractionation

Abstract

well established 70-eV electron impact fragmentation patterns of organic compounds or the performance of the quadrupole GC/MS system. The detection limits attained This technique made the method applicable to the analysis of relatively clean surface or drinking water. using conventional data acquisition were 1-50 ppm which makes the technique compatible with the concentrations of ACKNOWLEDGMENT organic compounds found in domestic sewage and other waste effluent water samples. Greater sensitivity, to about 50 ppb, was attained with real time data acquisition from subsets of the ions used in conventional mass spectrometry.We thank Tom Bellar of this Laboratory for the original suggestion to analyze tap water for chloroform. Sedimentation field-flow fractionation (SFFF), one member of the field-flow fractionation (FFF) class of techniques, is described and Its potential advantages and disadvantages for macromolecular and particle separatlons are discussed. Theoretical equations for retentlon and plate height are given along with an analysis of possible disturbances caused by relaxation effects, polydispersity, secondary flow, and sample size effects. The conclusions are tested experimentally using polystyrene latex particles having diameters from 907A to 4808A. Measured retention parameters are in excellent agreement with theory but a considerable discrepancy exists in piate height results. This is traced to a possible sample overloading effect. Particle fractionation is illustrated and the further potential of the method is discussed.

Sample overloading effects in polymer characterization by field‐flow fractionation

“…which approaches the limit R = 6X (7) for well-retained samples characterized by small values for R and A. However, in the case of thermal FFF, the applied temperature gradient results in a gradient in viscosity across the channel; this causes a departure from the normally parabolic velocity profile in the channel and in Eq.…”

Sedimentation Field-Flow Fractionation of Nonspherical Particles

“…where D is the diffusional coefficient for the particle and C [3], used to evaluate the constant when Eq.…”

Separation of fine particle dispersions using periodic flows in a spining coiled tube

“…A wide range of fields can be employed, leading to several subclasses of FFF (Giddings et al, 1981). The one most closely related to the new method is sedimentation field-flow fractionation (SFFF) (Giddings et al, 1974), which uses a centrifugal field. (A similar technique was independently developed by Berg and Purcell, 1967.)…”

“…This method is similar in some respects to parametric pumping (PP) (Wilhelm et al, 1966) and sedimentation field-flow fractionation (SFFF) (Giddings et al, 1974). It employs cyclic flow as does PP.…”