Micro-channel thermal field-flow fractionation: High-speed analysis of colloidal particles

Micro-thermal field-flow fractionation (mu-TFFF) was developed recently and applied for the characterization of the synthetic polymers and colloidal particles. In comparison with standard size TFFF channels, which were already used for the separation of the colloidal particles, the miniaturized channel allows one to shorten the time of the analysis and to achieve high,resolution if the separation is performed under optimized experimental conditions. The relaxation processes leading to the establishment of the initial steady state after the injection of the sample into the channel can influence the retention and contribute to the zone broadening. These processes are considerably influenced by the temperature, which has to be carefully chosen. The choice of a convenient flow rate represents a compromise between an optimum flow rate (which is too slow due to the low diffusion coefficients of the colloidal particles) and a reasonable flow rate which takes into account the injection period and the stop-flow procedure applied immediately after the injection of the sample in order to minimize the effect of the relaxation processes. All these parameters can easily be optimized in the mu-TFFF due to its high versatility and to an important decrease of the heat energy flux across the channel, allowing an independent control of the temperatures of the cold and hot walls. The mu-TFFF thus becomes high-performance method for the separation of the colloidal particles and for the determination of their particle size distribution (PSD).