An Agarose-Schiff’s Base Chelating Adsorbent for Preconcentration and Flame Atomic Absorption Spectrophotometric Determination of Cu(II) in Water Samples

Abstract

A recently synthesized naphthol derivative Schiff’s base, 2,2'-[1,2-ethanediyl-bis(1- nitrilopropylidyne)]bis(1-naphthalene), was covalently bonded to an epoxy activated agarose (Novarose) bead. Adsorption properties of the new adsorbent and effects of various parameters on the separation and column preconcentration of Cu²⁺ prior to its determination by flame atomic absorption spectrophotometric method were carefully studied. The optimum pH range for quantitative accumulation of copper was 5.7–7.0 and the binding capacity was calculated to be 14.4 (±0.4) mg Cu²⁺ per mL of the packed adsorbent. The analyte can be eluted with 2 mL of a 0.075 mol L^–1 HCl solution. The lowest adsorbent volume (packed in a 6 mm i.d. column) for achievement of a quantitative recovery was 0.2 mL. Using this volume, sample flow rates up to 7.5 mL min^–1 could be applied. Electrolyte, NaNO₃, concentrations up to about 0.5 mol L^–1 was tolerated by a 0.5 mL column. Enrichment of the analyte was quantitative in presence of Na⁺, K⁺, Mg²⁺ and Ca²⁺ concentrations of 40, 40, 3.3 and 8.2 g L^–1, respectively. Pb²⁺, Ni²⁺, Fe³⁺, Cr³⁺ and Zn²⁺ with concentrations of 15 to 20 mg L^–1 also had no effect on the analyte's signal. The maximum preconcentration factor obtained was 350, corresponding to an enrichment volume of 700 mL. A detection limit of 0.62 μg L^–1 was obtained. The method was successfully applied to the determination of copper in river and tap water samples.