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

Abstract

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 (BTCZinc(II), 600; BTCCadmium(II), 460; BTCMercury(II), 540 μM g–1; and PFZinc(II), 197; PFCadmium(II), 148; PFMercury(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.