How does molecular weight cut-off impact separation?

Generally, for most materials, when the molecular weight cut-off (MWCO) of a membrane increases (when the pore size becomes larger), it leads to an overall increase in permeability or permeate flux and an overall decrease in rejection coefficient. This occurs because larger pores allow molecules with a broader range of molecular weights (MW) to pass through the membrane.

Using membranes with a larger MWCO could potentially increase non-specific binding and permeation because these membranes offer larger surface areas. On the other hand, using membranes with low MWCO can enhance rate of recovery but they may also slow down ultrafiltration and result in retention of impurities with lower molecular weight.

Choosing an appropriate molecular weight cut-off membrane is crucial to ensure efficient separation.