Methods for identifying and quantitating host cell protein

A method for detecting and/or discriminating between protein contaminants of interest in an antibody preparation sample by a physical parameter, comprising:

• separating protein components of a sample by a physical parameter in one or more capillaries using capillary electrophoresis;
• immobilizing the protein components of the sample within the one or more capillaries;
• contacting the protein components within the one or more capillaries with a first primary antibody that specifically binds to a first protein contaminant of interest;
• detecting the binding of the first primary antibody, thereby detecting the first antibody of interest;
• contacting the protein components within the one or more capillaries with a second primary antibody that specifically binds to a second protein contaminant of interest;
• and
• detecting the binding of the second primary antibody, thereby detecting the protein contaminants of interest and discriminating between the antibodies in a sample.