Atomic Absorption Spectrometric Determination of Trace Amounts of Copper and Zinc after Simultaneous Solid-Phase Extraction and Preconcentration onto Modified Natrolite Zeolite

This work assesses the use of modified natural natrolite zeolite as an adsorptive material for the separation and preconcentration of trace amounts of ions. In this work we investigated the potential of modified natural natrolite zeolite for the simultaneous separation and preconcentration of trace amounts of copper and zinc ions. We have developed a simple, rapid, selective, sensitive and economical method for the simultaneous separation and preconcentration of trace amounts of copper and zinc in an aqueous medium using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as an analytical reagent. The sorption was quantitative in the pH range 7.5-9.5, whereas quantitative desorption occurred instantaneously with 5.0 mL of 2 mol L-1 nitric acid. Linearity was maintained between 0.05-6.0 μg mL-1 for copper and 0.02-1.5 μg mL-1 for zinc in the final solution. Ten replicate determinations of 1.0 μg mL-1 copper and 0.5 μg mL-1 zinc in a mixture gave mean absorbances of 0.1687 and 0.2788 with relative standard deviations of ±1.2% and ±1.3%, respectively. The detection limits were 0.03 ng mL-1 for Cu(II) and 0.006 ng mL-1 for Zn(II) in the original solution (3σbl/m). Different parameters, such as the effect of the pH, flow rate, breakthrough volume and interference of a large number of anions and cations, were studied and the proposed method was used for the determination of these metal ions in water as well as standard samples (e.g. Nippon Keikinzoku Kogyo (NKK) CRM, No. 916 and No. 920 aluminum alloy, National Institute for Environment Studies (NIES) No. 1 pepperbush and NIES No. 2 pond sediment). The determination of these metal ions in standard samples showed that the proposed method has good accuracy (recovery > 97%).