Widely used as a chromogenic reagent in analytical chemistry, particularly for the detection and quantification of iron(II) ions. It forms a stable, magenta-colored complex with Fe²⁺, making it valuable in spectrophotometric analysis at approximately 562 nm. The intense color development upon binding allows for high sensitivity and selectivity in iron assays. Commonly applied in environmental testing to monitor iron contamination in water and soil. Also utilized in biochemical research for studying iron ion transport and enzyme activity involving iron cofactors. Its sulfonic acid groups enhance water solubility, enabling use in aqueous systems without organic solvents.