Evaluation of pinched inlet channel for stopless flow injection in steric field-flow fractionation

In this article the concept of utilizing a pinched inlet channel for field-flow fractionation (FFF), in which the channel thickness is reduced over a substantial inlet segment to reduce relaxation effects and avoid stopflow, is evaluated for steric FFF using one conventional channel and two pinched inlet channels. It is shown that with the proper adjustment of flow-rate, the stopflow process in FFF can be completely avoided, thus bypassing the flow interruption associated with stopflow and reducing separation time. The maximum flow-rate than can be used for stopless flow operation without incurring zone distortion is shown to agree reasonably well with simple theory; slight departures from theory are attributed to the existence of reduced transport rates of large particles through thin channel structures.