Analytical Sciences

Preparation of a Fast-Flow Agarose-Based Chelating Adsorbent with a Novel Dioxime Derivative for Selective Column Preconcentration of Copper

Payman HASHEMI, Zohreh RAHMANI, Ali KAKANEJADIFARD, and Esmaiil NIKNAM

Lorestan University, Department of Chemistry, Khorram Abad, Iran

Fast-flow spherical homogeneous agarose beads were prepared by an emulsification method, and were cross-linked and activated by repeated treatment with allylbromide and bromine/water, followed by alkali. Bis(2-aminopyridyl)dioxime (APD) was synthesized by the reaction of 2-aminopyridine, and dichloroglyoxime and characterized by melting-point as well as IR, ¹HNMR, ¹³CNMR and MS spectroscopies. APD was chemically linked to activated agarose beads to be employed for the column preconcentration of metal ions. Capacity measurements for eight metal ions indicated a high selectivity of the adsorbent towards Cu²⁺ with a capacity of 25.7 µmol per ml packed adsorbent. A factorial design was used for optimization of the effects of 5 different variables on the recovery of Cu²⁺. Under the optimized conditions, Cu²⁺ was quantitatively accumulated on a 0.25 ml packed column of the adsorbent in the pH range of 4 to 6, and simply eluted with 2 ml of a 1 mol l^-1 hydrochloric acid solution. The column could tolerate salt concentrations up to 0.5 mol l^-1, sample flow rates up to 15 ml min^-1, and sample volumes beyond 1000 ml. Matrix ions of Na⁺, Mg²⁺ and Ca²⁺ and potentially interfering ions of Ni²⁺, Cd²⁺, Zn²⁺, Fe³⁺ and Co²⁺ with relatively high concentrations did not show any significant effect on the analyte's signal. Preconcentration factors up to 500 and a detection limit of 0.16 µg l^-1 were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked copper in river water and seawater samples resulted in quantitative recoveries.

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