Preconcentration of heavy metal ions with thermo-sensitive chitosan and atomic absorption spectrometric determination of trace cadmium in water

Abstract

Thermo-sensitive chitosans grafted with N-isopropylacrylamide copolymers having maleate or hydroxamate {poly(NIPAAm-co-MaA)-g-chitosan, poly(NIPAAm-co-MHA)-g -chitosan} were synthesized, and their dispersivities and adsorbtivities of metal ions were also investigated. The synthesized thermo-sensitive chitosans dispersed at 20°C, which is below the phase-transition temperatures, and aggregated at 50°C, which is above the phase transition temperatures. Every synthesized thermo-sensitive chitosan adsorbed Cu II, Cd II, and Pb II ions in the neutral pH range, quantitatively. Especially, poly(NIPAAm-co-MaA)-g-chitosan kept its quantitative adsorbtivity of metal ions through replicative adsorb/desorb processes. Twenty-times preconcentrations of 1.0 × 10 -9 mol dm -3 of Cu II, Cd II and Pb II were achieved with over 90% recoveries by using every synthesized thermo-sensitive chitosan. The combination of poly(NIPAAm-co-MaA)-g- chitosan used as an adsorbent and a graphite-furnace atomic-absorption spectrometry allowed to determine trace amounts of Cd II in tap water, drinking water, and river water. The atomic spectrophotometric determination of cadmium(II) with the thermoresponsive chitosan was also successfully applied to certified reference materials of river water. © 2007 The Japan Society for Analytical Chemistry.