Field-flow fractionation, FEE

Whole or degraded starch is currently analyzed by SEC, by the related technique of field flow fractionation (FEE), EIPLC in different forms, and by a range of physical and chemical techniques including microscopy (light and SEM), X-ray diffraction, differential scanning calorimetry, NIR and FTIR spectrometry, solid-state NMR, and most importantly by the use of such enzymes as the a- and S-amylases and amyloglucosidase. 

Another separation technique of particular application for proteins, high-molar-mass molecules, and particles is the general class known as field-flow fractionation (FEE) in its various forms (cross-flow, sedimentation, thermal, and electrical). Once again, MALS detection permits mass and size determinations in an absolute sense without calibration. For homogeneous particles of relatively simple structure, a concentration detector is not required to calculate size and differential size and mass fraction distributions. Capillary hydrodynamic fractionation (CHDF) is another particle separation technique that may be used successfully with MALS detection. 

Schure [35] compared different chromatographic method combinations on the basis of efficiency, sample dilution, and detectability. He investigated Capillary Electrophoresis (CE), Gas Chromatography (GC), Liquid Chromatography (LC), SupercriticalEluidChromatography (SEC), and field flow fractionation (FEE) in detail, while... 

Whether DLS, DWS, Mie scattering, or other applications in which unfractionated samples are analyzed, the resulting distributions produced by modern instruments, while frequently facile to obtain and neat in appearance, must be treated with caution, as there is usually a large amount of data smoothing, fitting, and assumptions applied in using inverse Laplace transform and several other commonly employed methods. The best means of finding distributions of size and mass continue to be fractionation methods, such as SEC [32-34], field flow fractionation (FEE) [35-37], capillary electrophoresis [38], capillary hydrodynamic fractionation [39], and so on. 

Fig. 1 Schematic representation of a mass spectrometer depicting its main components and the different modes used. Abbreviations DIP direct insertion probe DEP direct exposure probe GC gas chromatography LC liquid chromatography CE capillary chromatography TEC thin-layer chromatography FEE field-flow fractionation APCI atmospheric pressure ionization El electron impact Cl chemical ionization FAB fast-atom bombardment PD plasma desorption MALDI matrix-assisted laser desorption ionization ED laser desorption TSP thermospray ESI electron spray ionization HSI hypherthermal surface ionization Q quadropole QQQ triple quadropole TOE time-of-fiight FTMS Fourier transform mass spectrometer IT ion trap EM electrom multiplier PM photomultiplier ICR ion cyclotron resonance.

The group of flow FEE is the most improved separation technique within the FEE family. Particularly the asymmetrical flow field-flow fractionation (AF4) provides a broad range of application possibilities. In this case, the separation is caused by different diffusion coefficients (D) by inducing a flow field with a perpendicular liquid flow. A permeable wall (porous frit covered with an ultrafiltration membrane see Fig. 4.10b) allows the cross flow to act as force field. The retention time (t) is given by the following equation ... 

T. Provder, ed.. Chromatography of Polymers Characterization by SEC, Size Exclusion Chromatography and FEE Field Flow Fractionation, American Chemical Society, Washington, D.C., 1993. 

---