A new azo dye for colorimetric determination of lead(ii) ions.

A new azo dye, S9b (1-amino-4-[()-2-(8-hydroxyquinolin-5-yl)diazen-1-yl]-9,10-dihydroanthracene-9,10-dione), was developed and evaluated as a colorimetric chemosensor for lead(ii) ions. Upon Pb addition, the S9b solution color changed from rosy-brown to sandy-brown. The UV-vis spectrum of the S9b-Pb complex exhibited a hyperchromic shift compared to free S9b and a bathochromic shift relative to S9b complexes with other metal ions. Optimized conditions comprised an ethanol solvent system, pH 6.0, a reaction time of 2 min, and a 2 : 1 molar ratio of S9b to Pb.The response of S9b was linear at Pb concentrations of 3.90-9.36 μg mL. The calculated detection limit, quantitation limit and binding constant were 1.55 μg mL, 4.71 μg mL and 3.07 × 10 L g, respectively. Determination of Pb was not significantly affected by other interfering cations (Ag, Co, Cu, Fe, Fe, Na, K, Ni, Hg, Ca, Zn, Mg, and Al). The S9b-based method demonstrated recoveries of 100.03-103.11% and relative standard deviations (RSDs) of 0.06-2.07% for Pb in spiked water samples, with accuracy and precision comparable to atomic absorption spectroscopy (AAS). FTIR studies and DFT calculations indicated that Pb binding to S9b occurs the heterocyclic nitrogen and phenolic hydroxyl groups of the azo dye. The sensor demonstrated reusability following regeneration with EDTA, which dissociated the Pb complex. This study highlights the potential of the anthracene-9,10-dione-based azo dye as a simple, eco-friendly, and rapid chemosensor for Pb detection in aqueous systems.