Used primarily as a derivatizing agent in analytical chemistry, especially in the detection and quantification of amino acids and peptides. Its sulfonyl chloride group reacts readily with primary and secondary amines to form stable sulfonamide derivatives, which are often fluorescent or UV-active, making them suitable for detection in HPLC and other chromatographic methods. Also employed in the synthesis of fluorescent probes and labels due to its ability to enhance detectability in biological imaging. Additionally, it serves as a key intermediate in the preparation of quinoline-based pharmaceuticals and agrochemicals, where the sulfonyl functionality acts as a linker or activating group in further transformations.