Fluorescent Resin-Assisted Extraction for Selective Separation and Preconcentration of Mercury(II) and Its Online Detection

Dimethyldichlorosilane (DMDCS) driven silane coupling is enabled by productive immobilization of an azo-dye to inorganic carrier through m-nitroaniline as a bridging component. The material has been utilized for the selective sample cleanup of zinc­(II), cadmium­(II), and mercury­(II), respectively, extracted as [Zn₅(OH)₆(H₂O)₂]⁴⁺, [Cd₄(OH)₄(H₂O)₃]⁴⁺, and [Hg₄(OH)₃(H₂O)₂]⁵⁺. The corresponding luminescent nanomaterial was used for selective detection of mercury­(II) at trace level (LOD ≥ 0.04 × 10^–5 M) amid a matrix of possible interferences. Breakthrough capacity (BTC) and preconcentration factor (PF) for the respective metal ions (BTC_Zinc(II), 600; BTC_Cadmium(II), 460; BTC_Mercury(II), 540 μM g^–1; and PF_Zinc(II), 197; PF_Cadmium(II), 148; PF_Mercury(II), 145) were found to be excellent. Sequential separation of zinc­(II), cadmium­(II), and mercury­(II) was achieved by employing selective eluents (mineral acids of very low concentration, 5 × 10³ μM). BTC (530 ± 70 μM g^–1) was found to be the product of the amount of extractor frontier orbitals (132 μM g^–1) and polynuclear state of sorbed species, x (i.e., BTC = {amount of HOMO}× x; x = 4 for cadmium­(II), mercury­(II); and x = 5 for zinc­(II)). Along with these analytical qualities, ease of synthesis, high level of reusability (≤2700 cycles @ 95% exchange capacity), and chemical stability (post treatment BTC with 8 M HNO₃, 8 M HCl, and 5 M H₂SO₄ was ≤95%) is an insignia of the material.