Effect of channel width on the retention of colloidal particles in polarization, steric, and focusing micro-thermal field-flow fractionation.

The effect of the channel width on the performance of separation by micro-thermal field-flow fractionation (micro-TFFF) of the carboxylated polystyrene latex particles was studied by using the particles in diameter range from 100 nm to 3800 nm. It has been shown that the retention order follows the anticipated polarization, steric, and focusing mechanism in the corresponding size range and under the specific conditions, appropriate to each channel thickness. However, the attractive interactions of the particles with the accumulation wall can complicate the separation as has been proven by the experiments carried out by using the carrier liquids of different ionic strengths.

Micro-thermal focusing field-flow fractionation.

Focusing mechanism was effectively exploited to separate large (micrometer-size) particles by using new micro-thermal field-flow fractionation (micro-TFFF). It has been shown that the retention order of micrometer-size particles at high field strength can be explained by the mechanism of steric exclusion only at lowest flow rates of the carrier liquid. A simplistic, purely mechanical model of steric exclusion is not accurate to describe the retention at higher flow rates where the focusing phenomenon appears.