Investigation of steric transition with field programming in frit inlet asymmetrical flow field-flow fractionation.

Steric transition in flow field-flow fractionation (FlFFF) was investigated under field programming by varying the channel thickness of a frit inlet asymmetrical FlFFF (FI-AF4). Steric transition is a typical inversion in sample elution mode from the increasing order of diameter (normal mode) to the opposite order (steric mode). Owing to the co-elution of two different-sized particles in the steric transition region where particles elute by the combination of the two elution modes, a loss of information in determining the accurate size of sample components in field-flow fractionation occurs. In this study, the effect of field programming on the steric transition in FI-AF4 was examined with the increase in channel thickness in order to increase the diffusional contribution of particle retention with the simultaneous reduction of steric contribution. This study demonstrated that the steric inversion diameter can be increased to >1 μm by programming the crossflow rate and by increasing the channel thickness to 350 and 490 μm. The present study also investigated the effects of outflow rate and initial field strength on the particle separation in field-programmed FI-AF4.