Immunoaffinity purification is considered a subset of affinity chromatography utilizing an immunoglobulin as the biospecific ligand. The immunoglobulin can be either a polyclonal grouping of antibody molecules or a monoclonal antibody. (1)
Purification techniques target the binding of specific proteins from cell or tissue lysates to immobilized antibody groups like Protein A/G resin or Streptavidin. After a series of wash steps, the target molecule or protein is selectively eluted for analysis. Immunoaffinity applications range from clinical diagnostics to environmental monitoring.
There are several product types for immunoaffinity purification using Protein A/G or streptavidin such as prepackaged cartridges, spin columns and magnetic beads. Magnetic beads for use in isolation and separation of small molecules, proteins or antibodies are incubated with a sample. Unbound contaminants are washed from the bead and then the target bound molecules are eluted. Unlike cartridges or spin columns, magnetic bead purification methods can be automated, but still pose some problems. In addition to their costly nature, magnetic beads have been known to come loose and make their way into the injection system of the instrumentation (often LC-MS/MS), which can severely damage the instrument.