Trace measurement of lead and cadmium ions in wastewater samples using a novel dithizone-immobilizedmetal-organicframework-based μ-dispersivesolid-phase extraction

A low-cost, reliable, easy-to-perform, sensitive and environmentally friendly metal-organic framework (MOF)-based mu-dispersivesolid-phase extraction (mu-dSPE) method for extraction and graphite furnace atomic absorption spectrometry (GF-AAS) determination of lead and cadmium ions in several wastewater samples was successfully developed. Initially, a zinc-based MOF nanosorbent was prepared, immobilized with appropriate complexing agent dithizone (DTZ), characterized and eventually applied for the simultaneous extraction of the target ions. In practice, the application of the DTZ-based MOF nanosorbent led to improvements in the extraction efficiency. After the extraction of the target ions, the desorption process, which was facilitated with vigorous agitation, was performed by applying a small amount of a desorption solvent (inorganic acid, HNO3). In the next step, concentrations of the desorbed heavy metal ions were measured using GF-AAS. The parameters influencing the adsorption and desorption efficiencies were thoroughly evaluated followed by the establishment of optimal conditions. Under the optimum conditions, the calibration curves for respective Pb(II) and Cd(II) ions were linear over the concentration ranges 0.5-5.0 and 0.05-2.0 mu g l(-1). Relative recovery tests on spiked wastewater samples were performed with the results varying between 96% and 103%, whilst the analogous precisions were located in the range 1.8-3.1%. Finally, the mu-dSPE method in conjunction with GF-AAS was demonstrated to be fast, sensitive and cost-effective, and could be potentially used in environmental laboratories for the surveillance of lead and cadmium ions in various wastewater samples.