NUMERICAL-SIMULATION OF BAND-BROADENING DURING HYDRODYNAMIC RELAXATION IN FRIT-INLET FIELD-FLOW FRACTIONATION CHANNELS

The frit-inlet technique is a promising implementation of hydrodynamic relaxation of samples in field-flow fractionation (FFF). The optimiza tion of the process is of great importance in order to maximize overal l system efficiency. The mechanism of band-broadening that takes place during hydrodynamic relaxation has been examined using a three-dimens ional simulation of the flow inside the triangular end-piece of the ch annel. This is the first time this contribution to band-broadening has been considered and studied. Particle trajectories in the absence of a transverse field were numerically calculated, thereby isolating this effect from the familiar field-driven relaxation effect. As a first s tep towards an optimization of the system, the influence of the length of frit element was examined. Band-broadening was examined by determi ning the number of particles passing through the triangular end-piece as a function of transit time for a uniform particle distribution at t he injection point. Due to the complexity of the flow patterns within the system, it is concluded that such numerical simulations are necess ary for the optimization of the design and operation of this type of c hannel. (C) 1998 Elsevier Science B.V.