Flame Atomic Absorption Spectrometry Determination of Trace Amounts of Cadmium and Zinc in Water Samples after Preconcentration onto Modified Amberlite XAD-4 Resin

摘要

In the present article, a procedure for the simultaneous separation and preconcentration of trace amounts of cadmium and zinc is proposed. It is based on the adsorption of cadmium and zinc ions onto a column of Amberlite XAD-4 resin loaded with alumi-non reagent. Cadmium and zinc ions are quantitatively retained on the column in the pH range from 6.5-7.5, at a flow rate of 2 mL min~(-1). The cadmium and zinc ions are eluted with 5.0 mL of 5 mol L~(-1) HNO_3 solution. Cadmium and zinc are measured by flame atomic absorption spectrometry (FAAS). In the present case, 0.1 μg of cadmium and 0.5 μg of zinc can be concentrated in the column from 1000 mL of aqueous sample, where their concentrations are as low as 0.1 and 0.5 ng mL~(-1), respectively. The relative standard deviations, for seven replicated determinations of 1.0 μg mL~(-1) of cadmium and zinc, are 1.2 and 1.1%, respectively. The detection limits for cadmium and zinc in the original solution are 0.02 and 0.11 ng mL~(-1), respectively. The interference of a large number of anions and cations has been studied and the optimized conditions are utilized for the determination of trace amounts of cadmium and zinc in different environmental and standard samples.