Potentially, extraction techniques offer advantages such as higher capacity, better selectivity and integration between recovery and purification. Affinity extraction with organic solvents appears promising, provided that irreversible denaturation of the extracted biomolecules can be limited. Therefore, as a first essential step the influence of various organic solvents has been studied on the extraction of typical proteins (cytochrome c, myoglobin, human serum albumin HSA) and antibody (monoclonal Immunoglobulin G (IgG)) in liquid-liquid systems. For proteins, their conformation together with internal disulfide bonds give a picture of the predictable behaviour in contact with organic solvents. Depending on the type of protein the log P or the interfacial tension can give an indication about the overall stability. In the case of IgG existing solvents and selection methods used for small proteins are not suitable to define a good solvent for IgG free of stabilizers. However, when stabilizers and sugars are present in the buffer solution almost all the solvents tested show a good capacity to retain IgG concentration. Ionic liquids demonstrated considerably higher capacity to retain the IgG concentration than conventional organic solvents, however, do not completely stabilize monoclonal IgG in pure solution. (C) 2008 Elsevier B.V. All rights reserved.