Used as a pH indicator in analytical chemistry, particularly in titrations involving weak acids and strong bases. It provides a clear visual color change from colorless to blue in the pH range of approximately 9.3 to 10.5, making it suitable for detecting endpoint in alkaline conditions. Its phosphate-modified structure enhances water solubility and stability in aqueous solutions, allowing for consistent performance in biological and environmental testing. Also employed in some enzyme assays where pH monitoring is critical, due to its minimal interference with biochemical reactions.