Field-flow fractionation separation principles

In principle, all powerful element-specific methods that are able to monitor continuously the effluents of separation processes commonly in the range of a few mimin-1 and in element concentrations of some Klpg liter-1. A well-suited method is based on modern element-specific quadrupole mass spectrometry (MS) with an inductively coupled plasma (ICP) interface to the separation unit [e.g., liquid chromatography (LC) or field-flow fractionation (FFF)].Tlie ICP-MS detection can also be used for continuously characterizing the effluent of any kind of packed column (Metreveli and Frimmel, 2007). By this, the transport and elution properties of... 

Figure 13.6. Separation principle of field-flow fractionation (FFF) is based on physical interactions of particles within an applied field and subsequent field-induced migration to the FFF channel wall ( accumulation wall ). Molecules, depending on their size and diffusion coefficient, are distributed over different velocity lines of axial flow, and they separate accordingly. Larger particles possess less diffusional motion and higher interaction with the applied field hence, they will be caught up in slower-moving streams near the channel wall and elute later than smaller particles.

Although F(+) separation methods are powerful, they are relatively complicated in physicochemical detail. In this chapter we will provide a general framework for F(+) methodology, outline the principles and applications of field-flow fractionation, and introduce the theoretical basis of chromatography. Chromatography will be treated in greater detail in Chapters 10-12. 

Ion Chromatography, edited by James G. Tarter 38. Chromatographic Theory and Basic Principles, edited by Jan Ake Jonsson 39. Field-Flow Fractionation Analysis of Macromolecules and Particles, Josef Janca 40. Chromatographic Chiral Separations, edited by Morris Zief and Laura J. Crane 41. Quantitative Analysis by Gas Chromatography, Second Edition, Revised and Expanded, Josef... 

Separation Principle of Asymmetric Flow Field-Flow Fractionation... 

The particle sizing by field flow fractionation (FFF) is based on the different effect of a perpendicular applied field on particles in a laminar flow [63-66], The separation principle corresponds to the nature of the perpendicular field and may, for example, be based on different mass (sedimentation FFF), size (cross-flow FFF), or charge (electric-field FFF). Cross-flow FFF has been applied recently to investigate nanoemulsions, SLN, and nanostructured lipid carriers (NLC, particles composed of liquid and solid lipids) [58], Although all samples had comparable particle sizes in PCS, their retention in the FFF was very different. Compared to the spherical droplets of the nanoemulsion, SLN and NLC were pushed more efficiently to the bottom of the channel because of their anisotropic shape. Their very different shapes have been confirmed by electron microscopy. 

What is the basic principle of how large molecules are separated in field flow fractionation ... 

Magnetic field-flow fractionation (MFFF) has been the youngest subtechnique of FFF. So far the only work [66] dealing with MFFF defined elementary theoretical principles of the separation, and demonstrated in practice retentions of bovine serum albumin in the presence of nickel(II) ions in a magnetic field of 400 G. A coiled Teflon capillary with an inside diameter of 0.15 cm and length of 304 cm was used as a channel. In the absence of nickel(II) ions no retention was observed. 

Sedimentation Field Flow Fractionator. The chromatography-related principle of this particle size and size distribution analyzer is based upon the interaction of the particle suspension under centrifugal field motion in a thin channel. The elution time of the particles is a function of particle size, particle density, flow rate of mobile phase, density of mobile phase, and the centrifugal force applied. After the size separation has occurred, the particles are detected in the mobile phase using a turbidity detection system. The dynamic range of the instrument is dependent on particle density and operating conditions and is typically within 0.03 /rm— 1 /rm range. 

SEPARATION PRINCIPLE OF ASYMMETRIC FLOW FIELD-FLOW FRACTIONATION... 

Fig. 1 Principle of field-flow fractionation. 1—Solvent reservoir, 2-carrier liquid pump, 3—injection of the sample, 4— separation channel, 5—detector, 6—computer for data acquisition, 7—transversal effective field forces, 8—longitudinal flow of the carrier liquid. A—Section of the channel demonstrating the principle of polarization FFF with two distinct zones compressed differently at the accumulation wall and the parabolic flow velocity profile. B—Section of the channel demonstrating the principle of focusing FFF with two distinct zones focused at different positions and the parabolic flow velocity profile. C—Section of the channel demonstrating the principle of steric ITF with two zones eluting at different velocities according to the distance of their centers from the accumulation wall.

MAGNETIC FFF Magnetic field-flow fractionation has been studied in only a few cases dealing with theoretical principles of the separation and retention of bovine serum albmnin in the presence of nickel (II) ions in a magnetic field of 400G and retention of metal oxides. 

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