Acidic pH is commonly used to elute antibodies from Protein-A affinity column, although low pH may result in aggregation of the proteins. As an alternative, here arginine was tested as an eluent and compared with a more conventional eluent of citrate. Using purified monoclonal antibodies, recovery of antibodies with 0.1 M citrate, pH 3.8, was less than 50% and decreased further as the pH was increased to 4.3. At the same pH, the recovery of antibodies was greatly increased with 0.5 M arginine and more so with 2 M arginine. Even at pH 5.0, 2 M arginine resulted in 31% recovery, although the elution under such condition showed extensive tailing. Such tailing was observed at pH 3.8 when 0.1 M citrate was used. Size exclusion analysis indicated that the eluted antibodies were mostly monomeric whether eluted with citrate or arginine. This demonstrates the usefulness of arginine as an efficient eluent for Protein-A chromatography. (C) 2004 Elsevier Inc. All rights reserved.