Preparation of a Novel Agarose-Salen Adsorbent, and its Use for Efficient Column Preconcentration and Flame AAS Determination of Lead in Water

Abstract.

A cross-linked agarose (Novarose) support was chemically modified with a novel salen-type Schiff’s base; 2,2′-[1,2-ethandiyl bis(nitrilimethylidyne)] bis(orthocresol) and was used to develop an efficient, simple and low-cost method for matrix separation and preconcentration of lead in water. The binding capacity of the adsorbent, packed in a 6.5 mm i.d. glass column, was tested for different metal ions, and a capacity of 4973 (±95) µg per mL of packed adsorbent for triplicate measurements was obtained for lead at pH 6.0.

The effects of pH, ionic strength, buffer concentration, sample volume, eluent concentration and volume, and matrix ions on the column recovery of Pb²⁺ were carefully studied. Quantitative recoveries were obtained for the analyte in a pH range of 5.5 to 7.0. Enrichment volumes up to 300 mL and ionic strengths up to 0.5 mol L⁻¹ had no significant effect on the recovery of Pb²⁺. The method also tolerated relatively high concentrations of matrix ions such as Ca²⁺, Mg²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Mg²⁺ and Cd²⁺ with no considerable effect on the analyte’s signal. A few mL of 0.4 mol L⁻¹ hydrochloric acid was sufficient for quantitative elution of the analyte from a 0.5 mL column before its flame AAS determination. Preconcentration factors up to 60 and a detection limit of 2.5 µg L⁻¹ were obtained for the method. The precision, expressed as relative standard deviation, was 2.9% (at 100 µg L⁻¹) calculated from six replicate measurements. The method was successfully applied to the determination of Pb²⁺ in some river and spiked river water samples with good precision.