Definition: The term "TCO-PEG4-Acid" is a chemical compound from which other chemicals are derived, such as TCO (toxicological control agent) and PEG (polyethylene glycol). It represents the structure of the compound with molecular weight 512,694, where T = toluene, C= -C=C-alkyl group, O = oxygen, COO = carboxylic acid group, and I = isopropyl alcohol.