It is a dialdehyde and a member of benzaldehydes. A 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.

Ortho-Phthalaldehyde (OPA) 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, a known sensitizer.

The invention discloses application of 4-methoxyl ortho-phthalaldehyde in detection of ammonium and nitrogen in sea water and a detection method. The detection method includes that 1) sodium citrate solution, 4-methoxyl ortho-phthalaldehyde solution and sodium sulfite solution are added in ammonium and nitrogen working liquid in sequence, pH value of a system is regulated by sodium hydroxide solution, luminescence curves within a range of 390-550nm are detected in lambda ex=370nm after a certain reaction time, fluorescence intensity at the position of maximum emission wavelength is recorded, and a working curve of ammonium and nitrogen concentration and the fluorescence intensity at the position of the maximum emission wavelength; and 2) ammonium and nitrogen content in sample solution is quantified by the fluorescence intensity at the position of maximum emission wavelength according to the working curve.

O PHTHALADEHYDE AR