In the most straightforward case, constant crossflow profiles with crossflow rates between 0.3 and 0.6 mL/min are applied (Figure , left). In accordance with theory, retention times increase with increasing crossflow rates since the shear force presses the particles closer to the membrane where slower velocities are reached. While increased crossflow rates lead to higher resolutions of 1.5 (for 0.6 mL/min) compared to 1.0 (for 0.3 mL/min), a tendency of peak broadening indicating aggregation is observed. Seeking a compromise between high resolution and low aggregation, moderate crossflow rates are the best choice. The online recovery is the highest possible for moderate crossflow rates with 71% (for 0.4 mL/min) and 64% (for 0.5 mL/min). High losses of up to 20% of particles, even after PEGylation, are caused by the adsorption of particles on the membrane, tubes, and walls rather than bulk agglomeration. Since we used 5 kDa PEG and considerably high ionic strengths, bridging adsorption, where polymers such as PEG bridge the gap between particle and membrane and cause adsorption, can occur. However, there is no clear correlation between the resolution and the crossflow applied. Therefore, we consider crossflow-independent adsorption on tubes and walls to be the most potent particle loss mechanism.