Field-flow fractionation retention ratio

Provided that the correction for the zone broadening should not be applied, the first step in the data treatment is to convert the retention volumes (or the retention ratios R) into the corresponding molecular or particulate parameter, characterizing the fractionated species. Whenever the zone broadening correction procedure has to be applied, the data treatment protocol is modified, as described in the entry Zone Dispersion in Field-Flow Fractionation. [Pg.673]

The dependences of the retention ratio R on the size of the fractionated species (molar mass for the macromolecules or particle diameter for the particulate matter) are presented for various polarization FFF methods in the entry Field-Flow Fractionation Fundamentals. The raw, digitized fractogram, which is a record of the detector response as a function of the retention volume, is represented by a differential distribution function h(y). i can be processed to obtain a series of the height values hi corresponding to the retention volumes as shown in Fig. 1. Subsequently, the retention volumes are converted into the retention ratios Rf. [Pg.673]

The retention ratio R in polarization FFF is related to the retention parameter A (see the entry Field-Flow Fractionation Fundamentals) by... [Pg.673]

Figure 7.3.21. Field-flow fractionation (FFF). (a) Basic configuration of field-flow fractionation device and the detector response to a sample, (b) Retention ratio of species i vs. retention parameter X. (c) Schematic for flow field-flow fractionation with a cros ow. (d) Fhysical configuration/dimensions of a FFF channel with inlet/outlet. (e) Configuration of the channel in sedimentation FFF. (After Giddings (1993).)...

$Figure 7.3.21. Field-flow fractionation (FFF). (a) Basic configuration of field-flow fractionation device and the detector response to a sample, (b) Retention ratio of species i vs. retention parameter X. (c) Schematic for flow field-flow fractionation with a cros ow. (d) Fhysical configuration/dimensions of a FFF channel with inlet/outlet. (e) Configuration of the channel in sedimentation FFF. (After Giddings (1993).)...$

Retention In field-flow fractionation The retention ratio is generally defined as ratio of the average sample velocity v and the average solvent velocity (v(x)). Equal expressions are obtained by using the dead time to and the retention time of the sample Ir or the corresponding volumes Vo and Vr ... [Pg.83]

Equation (7) is a very important relationship because, with respect to Eq. (4), it indicates that in the most practical range of the linear flow velocities, above the optimal flow, the efficiency of the separation in FFF increases very rapidly with the retention ratio. This is rather an exceptional case among separation methods and the importance of this behavior has to be regarded with respect to the fact that the FFF methods and techniques are especially convenient for the fractionation of large and polydisperse species, such as macromolecules and particles. As the retention usually increases with the molar mass or particle size in polarization FFF, the efficiency is higher in the high molar mass or large particle size domain. This is one of the reasons why the FFF methods are particularly competitive in this field of application. [Pg.1750]

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