Field-flow fractionation fractionating power

In conclusion one can say that SEC is a very powerful method for polymer characterization, especially in combination with other composition sensitive or absolute calibration methods. A big advantage is also that the sample amount is fairly small, typically 10 mg. For more complex polymers, such as polyelectrolytes, enthalpic effects often become dominant and also for rather high molecular weight polymers chromatographic methods such as field-flow fraction (FFF) techniques might be more suitable. For fast routine measurements linear columns are often used. 

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... 

Beckett, R. (1991). Field-flow fractionation-ICP-MS A powerful new analytical tool for characterising macromolecules and particles. At. Spectrosc. 12,215-246. 

The 2D approach to separation offers not only a great increase in separation power over one-dimensional (ID) methods, but also greater versatility. We have noted that 2D separation requires the use of pairs of ID displacements. If N kinds of ID displacements can be employed, then N2 different pairwise combinations can be found for 2D use. For example, dozens of 2D methods can be envisioned that use a field-flow fractionation (FFF) mechanism these methods fall in four categories in which a given FFF mechanism can be combined with (1) another FFF subtechnique, (2) a form of chromatography, (3) an applied field (e.g., electrical), and (4) bulk flow displacement [20]. For separations generally, literally thousands of kinds of 2D separation systems are possible, although only a handful have been developed [8]. 

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. 

Fractionating Power in Sedimentation Field-Flow Fractionation with Linear and Parabolic Field Decay Programming, P. S. Williams, J. C. Giddings, and R. Beckett, J. Liq. Chromatogr., 10, 1961 (1987). 

Giddings JC, Kumar V, Williams PS, Myers MN (1990) Polymer separation by thermal field-flow fractionation high speed power programming. In Craver CD, Provder T (eds) Polymer characterization physical properties, spectroscopic, and chromatographic methods. American Chemical Society, Washington, DC, pp 1-21... 

The first volume concentrates on separation techniques. H. Pasch summarizes the recent successes of multi-dimensional chromatography in the characterization of copolymers. Both, chain length distribution and the compositional heterogeneity of copolymers are accessible. Capillary electrophoresis is widely and successfully utilized for the characterization of biopolymers, particular of DNA. It is only recently that the technique has been applied to the characterization of water soluble synthetic macromolecules. This contribution of Grosche and Engelhardt focuses on the analysis of polyelectrolytes by capillary electophore-sis. The last contribution of the first volume by Coelfen and Antonietti summarizes the achievements and pitfalls of field flow fractionation techniques. The major drawbacks in the instrumentation have been overcome in recentyears and the triple F techniques are currently advancing to a powerful competitor to size exclusion chromatography. 

Williams, P.S. and Giddings, J.C., Power programmed field-flow fractionation A new program form for improved uniformity of fractionating power,Anal. Chem., 59, 2038, 1987. 

Exner et al. (2000) combined laboratory TRXRF with asymmetric field-flow fractionation (AF4) methods to analyze the trace element composition and masses of colloidal humic substances. AF4 is a powerful technique for the separation of particles in a flow-field, and can be used with particles between 1 nm and 100 pm in size. The key aspect of the procedure is the relatively gentle handling of organic colloids with little... 

Kassalainen and Williams [135] coupled thermal field flow fractionation (ThFFF) and matrix-assisted laser desorption/ionisation time-of-flight mass spectroscopy (MALDI-ToF-MS) to yield a powerful combination of techniques for the analysis of polydisperse PS. ThFFF high selectivity and sensitivity to chemical composition were used to separate polydisperse polymers and polymer mixtures into the narrow polydispersity and homogeneous chemical composition fractions essential for MAT.DT-ToF-MS analyses. On the other hand, because it is possible to measure directly using MALDI-ToF-MS, it alleviates the need for polymer standards for ThFFF. Kassalainen and Williams [135] address the coupling of ThFFF and MALDI-ToF-MS and identify compatibility issues. Optimum conditions were determined and developed to maximise the capabilities of the combined technique. Depending on the polymer and the method of matrix-assisted laser desorption/ionisation (MALDI) sample deposition, fractions from 1-10 ThFFF runs were combined for MALDI-ToF-MS analysis. Binary solvents are used to enhance ThFFF retention and resolution of low (<15 kDa) polymers, and methods developed to allow routine MALDI-ToF-MS analyses of PS polymers up to 575 kDa. Overall, the compatibility of the two techniques was extended from several kilodaltons to several hundred kDa. Polymer... 

Field-flow fractionation (FFF) is a family of powerful separation techniques for the analysis of proteins, polymers, and particles. The FFF is divided into different subtechniques, which are related to the physical field acting perpendicirlar to the channel used in FFF. Examples are thermal FFF (Tfr-FFF), sedimentation FFF (Sd-FFF), electrical FET (E-FFF), and flow FFF (F-FFF). The separation range in FFF is typically very broad and small stmctiues of several nanometers in size up to hundreds of miaometer can be separated (Figirre 26). ... 

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