The thesis covers the preparation of low contamination Peroxynitrite (PO) using sodium-azide ozonization and determining the optimal steps for its preparation. Development of an analytical technique to follow the formation of Peroxynitrite in comparison to nitrite ion using ion chromatography and UV-vis spectrometry. A calibration curve was also determined to determine the concentration of each species during the ozonization Kinetics of Peroxynitrite decomposition reaction, determination of order and decomposition rate. The catalytic decomposition of Peroxynitrite with a Cu(II)/pydTyr complex with confirmation of a real catalytic process.