p-Nitrophenol in methanol is widely used as a reagent in biochemical and analytical laboratories. It serves as a substrate in enzyme assays, particularly for detecting phosphatase activity. When enzymes like alkaline phosphatase act on p-nitrophenol, they produce a yellow-colored product, allowing for easy quantification of enzyme activity through spectrophotometric methods. This application is crucial in clinical diagnostics, research, and pharmaceutical testing. Additionally, p-nitrophenol in methanol is utilized in organic synthesis as an intermediate for producing dyes, pharmaceuticals, and other nitroaromatic compounds. Its solubility in methanol enhances its effectiveness in these reactions.