Interpretation of thermal field-flow fractionation experiments in a tilted channel

Ryoo et al. [J. Kor. Chem. Soc., 39 (1995) 848] observed that the retention times of polymers in a tilted thermal held-flow fractionation channel significantly depend on the tilting angle, θ. Their results are quantitatively interpreted in the present study, It is found that the force directly exerted by the gravitational field on the macromolecules is much too small to account for the deviations observed. A reasonably good agreement is found between the experimental data obtained by Ryoo et al. and the retention times predicted by means of a model taking into account the free convection flow induced by the temperature dependence of carrier liquid density (thermogravitational effect). The measurement of the retention time at various θ, keeping flow and temperature differential constant, is suggested as a convenient method for determination of the sign of the Sorer coefficient of macromolecular or colloidal species.