Although the chaperon solvent plug was reported as a strategy to reduce aggregation before the column inlet in SEC (size-exclusion chromatography) protein refolding process, the appropriate position at which sample injected and the volume of the chaperon solvent plug have not been elucidated. Therefore, the detail of chaperon solvent plug design was investigated in this work. Our results indicated that, to ensure good performances in the SEC refolding process, the appropriate front and tail volumes of chaperon solvent plug should be slightly larger than the optimal values, which depend on the flow dispersion from the injector to the column inlet. However, with the front volume more than the optimum, it could have an adverse effect on activity recovery but not the mass recovery, while no effect at all if the tail volume exceeded the optimum. Furthermore, it might be economical to replace the eluent (refolding buffer) after the tail of chaperon solvent plug with a cheaper one. (C) 2011 Elsevier Inc. All rights reserved.