Magnetic Dispersive Micro-solid Phase Extraction of Ni(II) and Pb(II) on ZnFe2O4 Nanotubes for Their Determination by Inductively Coupled Plasma Mass Spectrometry

Magnetic ZnFe2O4 nanotubes (ZFONTs) were prepared as a new adsorbent for dispersive micro-solid phase extraction of Ni(II) and Pb(II) in environmental and biological samples prior to their determination by inductively coupled plasma mass spectrometry. The adsorption behaviors of the target ions on ZFONTs were studied. The results indicated that the analytes were quantitatively retained on ZFONTs in the pH range of 6.0-8.0, and eluted completely with 1.0 mL of 0.3 mol L-1 HNO3 solution. Separation of the sorbent from the aqueous phase was achieved by an external magnet to avoid tedious centrifugation or filtration steps. The main parameters influencing preconcentration and determination of the analytes were studied in detail. Under the optimum conditions, the detection limits of this method were 0.39 and 2.1 pg mL(-1) for Ni and Pb, respectively. The relative standard deviations were less than 6.0% (n=9, c=1.0 ng mL(-1)). This method was used for the determination of trace Ni(II) and Pb(II) in water samples and a certified reference material of bovine liver with satisfactory results. The recoveries for the spiked samples were in the range of 94.0-105%.