Micro-thermal field-flow fractionation: New challenge in experimental studies of thermal diffusion of polymers and colloidal particles

The theoretical principles and methodological aspects of the thermal field-flow fractionation applied to study the thermal diffusion of the macromolecules in solution and colloidal particles in suspension were developed. The theoretical analysis indicated that the miniaturization of the separation channel for thermal field-flow fractionation should improve the performance of this technique. A new microchannel was conceived and built. The experimental results obtained for polymer samples with an extended range of molar masses from relatively low up to ultrahigh and for the colloidal particles confirmed that the achieved resolution is the same but the versatility of the microchannel is superior to that of the standard size channels owing to the substantial decrease in the heat energy flux. This important improvement allows us to achieve very high resolution when applying constant-field-force operation, it makes it much easier to program the temperature drop which is an advantageous operational mode from the viewpoint of the time of analysis, and it extends considerably the range of perfectly controlled temperatures of the cold and hot walls. The sample amount needed for one analysis can be as small as a few nanograms.