The pressure normally
used in this kind of concentration process could have
influenced on the passage of compounds with molar mass
similar to that of the membrane, as suggested by Pinelo et al.
(2009). Van der Bruggen et al. (2008) suggested that for separation
of uncharged solutes by nanofiltration it is possible
that the membrane does not retain molecules with a variable
size, whether below or above the nominal pore size of
the membrane.