Used as a sensitive reagent for the detection and spectrophotometric determination of trace amounts of heavy metal ions, especially lead and mercury, in environmental, biological, and industrial samples. Forms colored complexes with metal ions, allowing for visual or instrumental analysis. Commonly applied in qualitative spot tests and extraction procedures due to its solubility in carbon tetrachloride, which facilitates separation of metal complexes from aqueous phases. Also employed in analytical chemistry for selective extraction and purification of metals.