CCD-Optimized UA-DMSPE Combined with DFT Assisted Selection of a Novel Anthraquinone-Based Sorbent for Pb(II) and...

In this study, a novel ultrasound-assisted dispersive micro solid-phase extraction (UA-DMSPE) method coupled with flame atomic absorption spectrometry (FAAS) was developed for the rapid, reliable, low-cost, and environmentally friendly determination of Pb-(II) and Cd-(II) ions in rice and paddy soil samples. Three novel anthraquinone-derived ligands, not previously reported in the literature, were synthesized and their metal-binding behaviors were evaluated through density functional theory (DFT) calculations. Based on Frontier molecular orbital (FMO), molecular electrostatic potential (MEP), and global reactivity descriptor analyses, Derivative 2, exhibiting the lowest HOMO-LUMO energy gap (ΔE = 2.1284 eV) together with the highest softness (σ = 347.8739) and electrophilicity index (ω = 28.2323), was identified as the most promising ligand for Pb-(II) and Cd-(II) coordination. Accordingly, Derivative 2 was selected and loaded onto silica to prepare a novel anthraquinone-functionalized sorbent and employed throughout all experimental studies. The principal parameters affecting extraction efficiency were optimized using a six-factor central composite design (CCD) coupled with response surface methodology (RSM), enabling statistical evaluation of the relationships between experimental variables and extraction recovery. Under optimized conditions, the developed method exhibited low limits of detection of 0.19 and 0.28 μg L^-1 for Pb-(II) and Cd-(II), respectively, wide linear working ranges (0.8-500 and 1.0-500 μg L^-1), and satisfactory precision (%RSD < 2.2). The proposed method demonstrated high tolerance toward coexisting ions and satisfactory recovery values in rice and paddy soil samples. Moreover, the simultaneous evaluation of rice and paddy soil samples enabled a reliable assessment of the potential transfer of heavy metals from soil to plant systems. The environmental performance of the proposed method was assessed using Analytical Eco-Scale, GAPI, and AGREE metrics, demonstrating high environmental compatibility owing to low reagent consumption, solvent-free operation, and minimal waste generation (AGREE score ≈ 0.84). Overall, the developed method combines DFT-assisted sorbent selection, CCD-based optimization, high selectivity, low detection limits, and strong green analytical performance, providing an effective and reliable analytical platform for the determination of Pb-(II) and Cd-(II) in rice and paddy soil samples.