During hydrolysis of lignocellulosic materials for ethanol production, compounds toxic for fermentation are formed. Ten nanofiltration (NF) and reverse osmosis (RO) membranes with low molecular weight cut-off (150–400 g mol 1 ) were screened on a flat-sheet plant for their ability to separate C5 and C6 sugars from acetic acid, furfural, 5-hydroxymethyl furfural and vanillin in a model solution. RO led to the highest sugars rejection (497%) but inhibitors transmission was low. NF membranes, especially NF270, NF- and NF245 (Dow) and DK (GE Osmonics) were found suitable for detoxification with glucose rejection 494% and inhibitors transmission 480%. At high Volume Reduction Ratio, VRR, transmission of inhibitors was still enhanced (496% at VRR¼8 and 10 bars). In these conditions, NF270 gave the highest permeate flux (20 L h 1 m 2 ) followed by DK, NF- and NF245. However, DK and NF- could be preferred because of lower sugar loss.