Preparation of dithizone grafted poly(allyl chloride) core–shell–shell magnetic composite microspheres for solid-phase extraction of ultra-trace levels of Pb(ii), Cu(ii) and Cr(iii) ions

Abstract

A novel adsorbent with high adsorption efficiency and adsorption capacity was synthesized and applied to capture heavy metal ions by coupling with ICP-OES analysis. The adsorbent consists of a magnetite (Fe₃O₄) core, a shell composed of polymerized 3-(trimethoxysilyl)propyl methacrylate, and another poly(allyl chloride) shell composed of plenty of repetitive units, on which the complexing agent of dithizone was grafted by reaction with side chains of the polymer. Compared with traditional adsorbents, the core–shell–shell magnetic composite microspheres have advantages of quick magnetic separation, excellent mechanical strength and high adsorption capacity. The adsorbent was characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, vibrating sample magnetometer, X-ray photoelectron spectrum, nitrogen adsorption surface area (BET), and FT-IR. Effects of enrichment conditions including pH, amount of adsorbent and elution conditions, interference of other coexistent ions, and the kinetics characterization and adsorption capacity of the adsorbent were studied. Under the optimized conditions, the limits of detection of Pb(II), Cu(II) and Cr(III) ions were 0.87, 0.079 and 0.029 μg L⁻¹, respectively. The RSDs (c = 10 μg L⁻¹, n = 7) were 2.33%, 5.20% and 1.30%, respectively. This adsorbent was successfully applied to the analysis of certified reference materials, viz. a multi-element stock standard solution [(GBW(E)082083] and tea-leaf [GBW(E)080001], and environmental and biological samples.