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

A new azo dye, S9b (1-amino-4-[(E)-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(2+) addition, the S9b solution color changed from rosy-brown to sandy-brown. The UV-vis spectrum of the S9b-Pb(2+) 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(2+).The response of S9b was linear at Pb(2+) concentrations of 3.90-9.36 μg mL(-1). The calculated detection limit, quantitation limit and binding constant were 1.55 μg mL(-1), 4.71 μg mL(-1) and 3.07 × 10(4) L(2) g(-2), respectively. Determination of Pb(2+) was not significantly affected by other interfering cations (Ag(+), Co(2+), Cu(2+), Fe(2+), Fe(3+), Na(+), K(+), Ni(2+), Hg(2+), Ca(2+), Zn(2+), Mg(2+), and Al(3+)). The S9b-based method demonstrated recoveries of 100.03-103.11% and relative standard deviations (RSDs) of 0.06-2.07% for Pb(2+) in spiked water samples, with accuracy and precision comparable to atomic absorption spectroscopy (AAS). FTIR studies and DFT calculations indicated that Pb(2+) binding to S9b occurs via the heterocyclic nitrogen and phenolic hydroxyl groups of the azo dye. The sensor demonstrated reusability following regeneration with EDTA, which dissociated the Pb(2+) 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(2+) detection in aqueous systems.