TY - JOUR
T1 - Enhanced Mass Selectivity in Thermal Field-Flow Fractionation Due to the Temperature Dependence of the Transport Coefficients
AU - Ko, Gwon-Hee
AU - Richards, Robyn
AU - Schimpf, Martin
PY - 1996/7/1
Y1 - 1996/7/1
N2 - 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/D T 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 the concentration profile. When the temperature dependence of D/D T is removed, the selectivity decreases from 0.64 6 to 0.57 4 . Although it does not constitute proof, the lower value is consistent with D T being independent of
AB - 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/D T 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 the concentration profile. When the temperature dependence of D/D T is removed, the selectivity decreases from 0.64 6 to 0.57 4 . Although it does not constitute proof, the lower value is consistent with D T being independent of
UR - https://scholarworks.boisestate.edu/chem_facpubs/55
UR - http://dx.doi.org/10.1080/01496399608001332
U2 - 10.1080/01496399608001332
DO - 10.1080/01496399608001332
M3 - Article
JO - Chemistry and Biochemistry Faculty Publications and Presentations
JF - Chemistry and Biochemistry Faculty Publications and Presentations
ER -