Enhanced Mass Selectivity in Thermal Field-Flow Fractionation Due to the Temperature Dependence of the Transport Coefficients
| Autor: | Martin E. Schimpf, Gwon Hee Ko, Robyn Richards |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
chemistry.chemical_classification
Field flow fractionation Process Chemistry and Technology General Chemical Engineering Diffusion Thermodynamics Filtration and Separation General Chemistry Fractionation Polymer Thermal diffusivity Ethylbenzene chemistry.chemical_compound chemistry Molar mass distribution Selectivity |
| Zdroj: | Separation Science and Technology. 31:1035-1044 |
| ISSN: | 1520-5754 0149-6395 |
| Popis: | Mass selectivity in thermal field-flow fractionation (ThFFF) is governed by the dependence of molecular weight M on the ratio of the diffusion coefficient D to the thermal diffusion coefficient D T. Although studies indicate that D T is independent of molecular weight in homopolymers (meaning that mass selectivity depends on differences in D alone), the greatest possible dependence of D on M predicted by polymer theory is not enough to account for the selectivity obtained in certain polymer-solvent systems. However, the increased selectivity can be explained by the temperature dependence of D/D T. Thus, lower molecular weight polymers, which are less compressed against the cold wall, experience a higher mean temperature. Since values of D/DT increase with temperature, the decrease in retention with M is greater than that predicted without considering the temperature dependence. We quantify the increased selectivity for polystyrene in ethylbenzene using a temperature-dependent value of D/D T in th... |
| Databáze: | OpenAIRE |
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