Laboratory data show that the optimum flow rate of silica gel flash columns is decided by the length and width of columns and the property of gel. To be more specific, longer, and narrower columns will provide more theoretical plates that are able to affect the flow rate. When referring to the resolution, it is influenced by the stationary phase.
If the stationary phase or the gel which is arranged in the columns is more balanced and with smaller particle size, the silica gel flash columns can provide better resolution. In general, the smaller particle size and the larger superficial area mean higher resolution.
Managing all the factors to optimize the purity of components and the recovery of silica gel flash columns could be very complex because they have a mutual effect. However, different results will be made when in independent testing. In other words, the selectivity of the mobile phase has the most profound effect on separation, but it is also decided by the volume of columns and the selection of solvent.
In fact, before the start of any true experiment, settings of silica gel flash columns need to be tested or calculated. If the data from TLC are available, then the optimal settings can be calculated.