O-Phthalaldehyde (OPA) is a chemical reagent that forms fluorescent conjugation products with primary amines. It is used for the detection of many biogenic amines, peptides, and proteins in nanogram quantities in body fluids. O-Phthalaldehyde is approved by FDA for use in test systems to detect blood urea nitrogen (BUN) for the diagnosis and treatment of certain renal and metabolic diseases. OPA is also a known desinfectant and has been approved for high-level sterilization of heat-sensitive medical instruments and is increasingly being used as a replacement in the healthcare industry for glutaraldehyde. OPA has also been approved for use as an indoor antimicrobial pesticide; an intermediate for the synthesis of pharmaceuticals, medicines, and other organic compounds.