Validated Spectrophotometric Monitoring of Hazardous Cd(II) and Pb(II) in Environmental Samples Using a Dithiocarbamate Ligand: Analytical Reliability, MP‐AES Comparison, and Bio‐Computational Insights

ABSTRACT

Cadmium and lead are priority hazardous pollutants that pose serious ecological and human health risks, necessitating reliable and cost‐effective monitoring. This study employed the sulfur‐rich heterocyclic ligand 4‐methylpiperazine dithiocarbamate (4‐MPdtc) as a selective complexing agent for the spectrophotometric determination of Cd(II) and Pb(II) in aqueous and food samples. The ligand and its metal complexes were synthesized under controlled alkaline conditions and characterized by FTIR, XRD, TGA and CV, confirming sulfur coordination, chelation‐induced structural transformation, enhanced thermal stability and distinct redox behavior. Stable colored Cd(II) and Pb(II) complexes formed in an aqueous‐acetonitrile medium exhibited absorption maxima at 360 and 420 nm, respectively. The proposed method showed excellent analytical performance, with linear ranges of 0.40–10.06 µg mL ⁻¹ for Cd(II) and 0.55–11.12 µg mL ⁻¹ for Pb(II) ( R ²  ≥ 0.995); detection limits of 0.38 and 0.46 µg mL ⁻¹ , while quantification limits of 1.15 and 1.40 µg mL ⁻¹ , for Cd(II) and Pb(II) respectively. Analysis of spiked vegetable and water samples achieved recoveries of 97.2%–99.2% for Cd(II), whereas 97.1%–98.9% for Pb(II), with RSDs below 2.0%. Validation against MP‐AES confirmed the method's accuracy, yielding recoveries of 98.5%–100.5% for Cd(II) and 98.0%–100.1% for Pb(II) with low RSDs. The complexes also exhibited enhanced antimicrobial and antioxidant activities, while DFT calculations revealed significant charge delocalization and a HOMO‐LUMO energy gap of 8.78 eV, indicating high kinetic stability. Collectively, these findings establish 4‐MPdtc as a sensitive, accurate and multifunctional ligand for Cd(II) and Pb(II) determination with promising applications in environmental monitoring.