Schiff Base-Derived Colorimetric Chemosensor for Fe³⁺ Detection: Synthesis, Mechanistic Insights, and Real-World Applications in Water Quality Monitoring.

A Schiff base colorimetric chemosensor (H₂L), synthesized from 2-hydroxy-1-naphthaldehyde and anthranilic acid, was developed for selective Fe³⁺ detection. In a DMF:H₂O (9:1, v/v) medium, H₂L exhibited a distinct and selective response to Fe³⁺ among common competing cations, producing a visible color change from yellow to black and a new broad absorption band at 504 nm. Job's plot indicated a 1:1 binding stoichiometry, and the association constant was 2.87 × 10⁴ M⁻¹. The sensor showed a low detection limit of 3.71 μM by UV-Vis titration, and its practical applicability was validated by spike-recovery analysis in real water samples (recoveries 91.04%-100.94%). A paper-strip assay enabled rapid on-site screening with smartphone image analysis, achieving an LOD of 50.7 μM. These results highlight H₂L as a simple and effective platform for Fe³⁺ monitoring in water-relevant matrices.