2,3-dihydroxypyridine loaded amberlite XAD-2 (AXAD-2-DHP): Preparation, sorption-desorption equilibria with metal ions, and applications in quantitative metal ion enrichment from water, milk and vitamin samples

2,3-Dihydroxypyridine loaded (via -N = N-linker) Amberlite XAD-2 (AXAD-2-DHP) was prepared and characterized by elemental analyses, TGA and FIF-IR spectra. It (1 g packed in a column of 1 cm diameter; surface area 135.5 m(2)g(-1)) was found to be an effective solid phase sorbent for enriching Zn2+, Mn2+, Ni2+, Ph2+, Cd2+, Cu2+, Fe3+ and Co2+ at PH 3.5 to 7.0 using flow rates between 1.0 - 5.0 mL min(-1). For desorption (recovery 97.0 - 99.8%) of the metal ions, 8 to 10 mL of 2.0 mol L-1 HCl or 1.5 mol L-1 HNO3 at a flow rate of between 2.0 and 4.0 mL min(-1) were found most suitable. The t(1/2) (time for 50% sorption) is between 2 and 10 min when a 50 mL solution (containing a total amount of metal of 2 mg) was equilibrated with 0.5 g of resin. Sorption of all metal ions except Pb2+ follows the Langmuir model, whereas for Pb the data fits with the Freundlich model. The sorption capacity is between 60.7 (for Cd) and 406.7 (for Cu) mu mol g(-1). The resin can withstand an acid concentration of <= 6 mol L-1 and can be reused for thirty cycles of sorption-desorption. The preconcentration factor varies between 100 and 300. For Cd, Ni and Cu the sorption capacity of 2,3-dihydroxypyridine loaded cellulose is lower than that of the present resin. The tolerance limits of electrolytes, humic acid, complexing agents, Ca2+ and Mg2+ in the enrichment of all metal ions are reported. The limits of detection are 3.88, 5.37, 8.72, 13.88, 4.71, 1.24, 0.59 and 0.30 mu g L-1 for Zn2+, Mn2+, Ni2+, Pb2+, Cd2+, Cu2+, Fe3+ and Co2+, respectively. The calibration curves for flame AAS determination were linear in the ranges 0.018-1.0, 0.067-5.0, 0.2-5.0, 0.9-20, 0.028-2.0, 0.077-5.0, 0.19-10 and 0.1-3.5 mu g mL(-1), respectively. All the eight metal ions in river and synthetic water samples, Co in vitamin tablets and Zn in milk samples have been quantitatively enriched with Amberlite XAD-2-DHP and determined by flame atomic absorption spectrometry.