The reason for setting ≥1:1 as the target effective filtration area to volume ratio (EFA/V) for filters is to allow for a higher volume of extraction solvent for recirculation.
We acknowledge that the target surface area to volume ratio (SA/V) of ≥6:1 is difficult to achieve for most test items. Thus, it is accepted to use a lower SA/V than the target, as long as the SA/V arrived at is greater than the SA/V in the component’s intended use.