Mobile phase containing arginine provides more reliable SEC condition for aggregation analysis.

Loss of protein aggregates due to matrix protein interaction during SEC often causes underestimation of aggregate content in the quality control of pharmaceutical proteins. Since new columns especially show stronger tendency to bind proteins, an effort should be made to suppress protein adsorption. We examined the effects of arginine on protein binding to SEC columns and found that loss of aggregates was reduced in the presence of arginine, leading to a reliable estimate of aggregate content even with newly used column and small protein load. This is not due to increased ionic strength, as NaCl resulted in increased protein loss. (c) 2009 Wiley-Liss, Inc. and the American Pharmacists Association.