Polyethylene glycol (PEG) is a family of long chain polymers attached to a glycerine backbone. PEG is a nonionic, nontoxic, biocompatible, strongly hydrophilic polymer. Polyethylene glycol is commonly used to fuse B-cells with myeloma cells in monoclonal antibody production. Anti-PEG antibodies can be used to monitor a drugs pharmacokinetics, including distribution, metabolism and excretion. In addition, PEG antibodies can be used for the quality control of pegylated molecules in ELISA, WB and flow cytometery.