Used as a sensitive reagent for the spectrophotometric determination of trace amounts of copper(II) ions in environmental and biological samples. It forms a stable, intensely colored complex with copper that allows detection at very low concentrations, typically in the parts-per-billion range. The reaction is selective in slightly acidic to neutral conditions, minimizing interference from other metal ions. Commonly applied in water quality testing, industrial effluent analysis, and monitoring copper levels in biological fluids. Also utilized in analytical chemistry for developing colorimetric sensor strips and in quality control processes within the pharmaceutical and electronics industries where precise metal ion control is critical.