Dispersive micro-solid phase extraction using magnetic ZnFe2O4 nanotubes as adsorbent for preconcentration of Co(II), Ni(II), Mn(II) and Cd(II) followed by ICP-MS determination

In this work, magnetic ZnFe2O4 nanotubes (ZFONTs) were synthesized, characterized and used as adsorbent for dispersive micro-solid phase extraction of Co(II), Ni(II), Mn(II) and Cd(II) before their determination by inductively coupled plasma mass spectrometry. Adsorption behaviors of target ions on ZFONTs were investigated. The results showed 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 0.4 mol L-1 HNO3. The separation of sorbent from aqueous phase was performed by an external magnet to avoid tedious centrifugation or filtration steps. Main parameters affecting preconcentration and determination of the analytes were studied in detail. Under optimum conditions, detection limits for Co(II), Mn(II) and Cd(II) were 0.10, 1.2, 3.7 and 0.09 pg mL(-1), respectively. Relative standard deviations were < 4.5% (n = 9, c = 1.0 ng mL(-1)). This method was verified by analysis of Co(II), Mn(II) and Cd(II) in environmental and biological samples, including water samples and certified reference materials of mussel (GBW 08571) and human hair (GBW 09101).