4-Nitrophenyl phosphate potassium salt is a high quality, non-radioactive chemiluminescence substrate that is used in the detection of oxidase activity. This product can be used to measure the activity of peroxidase and catalase enzymes, as well as the accumulation of hydrogen peroxide. It also has been shown to be a ligand for some sulfhydryl groups and an inhibitor of phosphatases. 4-Nitrophenyl phosphate potassium salt has been tested for its ability to inhibit bacterial growth and fluorescence by staining cells. This product has also been shown to have bioluminescent properties and can be used for diagnostics or culture media.