Used as a sensitive analytical reagent for the colorimetric detection of metal ions, particularly copper(II) and iron(III). It forms highly colored complexes with these metals, allowing for visual or spectrophotometric determination at trace levels. Commonly applied in environmental monitoring to assess metal contamination in water and soil samples. Also utilized in pharmaceutical analysis for metal impurity testing. Its sharp color change upon metal binding makes it suitable for use in test strips and sensor devices. Exhibits good selectivity and sensitivity in alkaline or mildly buffered solutions.