Thermal field-flow fractionation retention

Cao, W.J. Marcus, M.N. Williams, P.S. Giddings, J.C. Sample mass effects on thermal field-flow fractionation retention and universal calibration. Int. J. Polym. Anal. Charact. 1998, 4,407. 

Sisson, R.M. Giddings, J.C. Effects of solvent composition on polymer retention in thermal field-flow fractionation Retention enhancement in binary solvent mixtures. Anal. Chem. 1994, 66, 4043 053. 

Schimpf ME, Wheeler LM, Romeo PF (1993) Copolymer retention in thermal field-flow fractionation dependence on composition and conformation. In Provder T (ed) Chromatography of polymers characterization by SEC and FFF. American Chemical... 

The early research of Myers et al. [1,2] shows that polymer thermal field-flow fractionation (ThFFF) retention and thermal diffusion are solvent dependent. Recently, Sisson and Giddings [3] indicated that polymer ThFFF retention could be increased by mixing solvents. Rue and Schimpf [4] extended the molecular-weight range that can be retained by ThFFF to much lower molecular weights (<10 kDa) by using solvent mixtures without using extreme experimental conditions. There are several other reports on the effect of solvents on polymer retention, selectivity, and the universal calibration in FFF in last few years [5]. 

The retention of polymer molecules in thermal field-flow fractionation is determined by the diffusion coefficient and the thermal diffusion coefficient Dj, illustrated approximately by [8]... 

It is discussed in more detail below. The most basic chromatographic technique is adsorption chromatography [82,83], in which separation arises from variation in the retention of the chain units or functional groups, due to their interaction with a stationary surface. Other techniques rely on rates of sedimentation [84,85], and diffusion-adsorption phenomena (thin layer chromatography [TT-C]) [86, 87]. Thermal diffusion is the basis for thermal field flow fractionation (TFFF) [88-91], discussed later. 

Janca, J. Micro-thermal field-flow fractionation of colloidal particle Effect of temperature on retention and relaxation processes. CoU. Czech. Chem. Commun. 2003, 68, 672. Janca, J. Bemeron, J.-R Boutin, R. Micro-thermal field-flow fractionation New high-performance method for particle size distribution analysis. J. Coll. Interf. Sci. 2003,260, 317. Janca, J. Micro-channel thermal field-flow fractionation High-speed analysis of colloidal particles. J. Liq. Chromatogr. Relat. Technol. 2003, 26, 849. 

Janca, J. Martin, M. Influence of operational parameters on retention of ultra-high molecular weight polystyrenes in thermal field-flow fractionation. Chromatographia 1992,34,125. Semyonov, S.N. Kuznetsov, A. A. Zolotaryov, P.P. Theoretical examination of focusing field-flow ftactionation. J. Chromatogr. 1986, 364, 389. 

Thermal field-flow fractionation (ThFFF) can he applied to the analysis of virtually any polymer or copolymer that can be dissolved in an organic solvent, subject to low-molecular-weight limitations discussed in this entry. Water-soluble polymers are more difficult to separate because thermal diffusion, and therefore retention, is weak in water and other protic solvents. Still, certain non-ionic polymers can be separated, and with the use of mobile phase additives, even charged materials have been retained. Proteins, on the other hand, have not been successfully separated by ThFFF. 

Schimpf, M.E. Wheeler, L.M. Romeo, P.F. Copolymer retention in thermal field-flow fractionation. In Chromatography of Polymers Characterization by SEC and FFF Provder, T., Ed. ACS Publications Washington, DC, 1993,63-76. 

Jeon, S.J. Nyborg, A. Schimpf, MF. Compositional effects in the retention of colloids by thermal field-flow Fractionation. Anal. Chem. 1997, 67, 3442 3450. 

Regazzetti, A. Hoyos, M. Martin, M. Influence of operating parameters on the retention of chromatographic particles by thermal field-flow fractionation. Anal. Chem. 2004,... 

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... 

X HERMAL FIELD-FLOW FRACTIONATION (ThFFF) separates polymers according to their molecular weight and chemical composition. The molecular weight dependence is well understood and is routinely used to characterize molecular weight distributions (1-4). However, the dependence of retention on composition is tied to differences in the thermal diffusion of polymers, which is poorly understood. As a result, the compositional selectivity of ThFFF has not realized its full potential. How-... 

The understanding of the effects of sample concentration (sample mass) in field-flow fractionation (FFF) has being obtained gradually with the improvement of the sensitivity (detection limit) of high-performance liquid chromatography (HPLC) detectors. Overloading, which was used in earlier publications, emphasizes that there is an upper limit of sample amount (or concentration) below which sample retention will not be dependent on sample mass injected into the FFF channels [1]. Recent studies show that such limits may not exist for thermal FFF (may be true for all the FFF techniques in polymer separation), although some of the most sensitive detectors on the market were used [2]. 

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