Dansyl-L-leucine cyclohexylammonium salt is a fluorescent derivative of L-leucine, commonly used as a reference standard in high-performance liquid chromatography (HPLC) and capillary electrophoresis with fluorescence detection. It serves as an internal standard for the quantitative analysis of amino acids and peptides in biological samples due to the strong UV-induced fluorescence of its dansyl group. This compound is particularly valuable in trace-level detection in pharmaceutical, biochemical, and proteomic research. Additionally, it is employed in studies of chiral separations and enzyme kinetics where fluorescent labeling is required.