Efficient determination of some potentially toxic metal ions from real samples via modified nano-γ-alumina-based solid-phase extraction followed by flame atomic absorption spectrometric analysis

In the current research work, trace amounts of the Ni(II), Cu(II), Ag (I) and Zn(II) ions in water, cabbage and pomegranate juice were determined via the solid-phase extraction approach based on a new selective adsorbent in the continuous mode followed by flame atomic absorption spectrometry. This efficient and safe sorbent was easily prepared from the immobilisation of 2-(5-bromo- 2-pyridylazo)-5-diethylaminophenol (5-BrPADAP), as a selective chelating agent, onto nano-gamma-alumina coated with sodium dodecyl sulphate. Nano-gamma-alumina was successfully synthesised by the solution combustion procedure and was subsequently analysed by various techniques including SEM, XRD and BET. The parameters involved in the metal ions extraction including the sample pH and volume, amount of sorbent, flow rates of the sample and the eluent, and type and concentration of the eluting agent were optimised. Under the optimal operating conditions, the proposed sample preparation method provided the good linear dynamic ranges (LDRs) 6-300, 4-300, 4-110 and 4-300 mu g L-1 for the Ni(II), Cu(II), Ag(I) and Zn(II) ions, respectively, with the correlation of determinations (R(2)s) higher than 0.99. The detection limit (LOD) and repeatability (RSD%) values (n = 8) obtained were found to be in the ranges of 1.50-2.00 mu g L-1 and 4.44-5.52%, respectively. The calculated enrichment factors were found to be 166.6, 166.6, 200 and 200 for the Cu(II), Ag(I), Ni (II) and Zn(II) ions, respectively. According to the adsorption studies, the Freundlich isotherm and the pseudo-second-order model showed reasonable fits to the experimental data. Also, thermodynamic studies demonstrated that the adsorption process was spontaneous and exothermic.