Used as a sensitive reagent for the colorimetric determination of metal ions, especially copper(II), in environmental and industrial samples. It forms highly colored complexes with copper, allowing detection at low concentrations through visible color change, typically from yellow to pink or red. Commonly applied in water quality testing, including drinking water, wastewater, and soil extracts, due to its selectivity and ease of use. Also utilized in analytical chemistry for spectrophotometric assays and in some biochemical protocols where metal ion monitoring is required.