When performing separation of serum protein or iso LDH-isoAmylase-iso CK or iso phosphatase, it may happen that a protein (immunoglobulin or enzyme) binds to another protein (such as an immuno complex) or is present under a dimer, tetramer form.
It is suggested that you displace these molecules before placing them into solution for HPCE analysis. One way to accomplish this is to incubate the proteins for 30 minutes at 37C, 100ul of serum with 1-2 mg of Ficin (Sigma Catalog No. F3266).