Preconcentration and Determination of Cadmium by GFAAS after Solid-Phase Extraction with Synthetic Zeolite

The solid-phase extraction (SPE) method for the preconcentration of trace amounts of cadmium using synthetic zeolite A-4 and its determination by graphite furnace atomic absorption spectrometry (GFAAS) was investigated. The preconcentration conditions, such as the optimum pH range of the sample solution for the adsorption of cadmium and the kind of acid solution for dissolving the cadmium-adsorbed synthetic zeolite A-4, as well as the measurement conditions for the determination of cadmium by GFAAS, e.g., the ashing and atomizing temperature, were investigated. Quantitative recovery of cadmium onto zeolite A-4 from the sample solution over the pH range 2.0-9.0 was achieved by the batch method. After the solid-phase (cadmium-adsorbed zeolite A-4) was separated from the sample solution by a membrane filter, it was dissolved in 2.0 cm3 of 2.0 mol dm−3 nitric acid. An aliquot of the resulting solution was injected into the graphite furnace. In GFAAS measurements an alternate gas (Ar, 90%; O2, 10%) was used as a sheath gas, and the ashing temperature and atomizing temperature were 400°C and 1600°C, respectively. The detection limit (3σ) for cadmium was 0.002 μg dm−3. The relative standard deviation at 0.010 μg dm−3 was 3.5-4.5% (n = 5). The proposed method has been successfully applied to the analysis of trace cadmium in environmental water samples.