On-line Micro-Packed Column Solid-Phase Extraction of Cadmium Using Metal-Organic Framework (MOF) UiO-66 with Posterior Determination by TS-FF-AAS

Metal-organic framework (MOF) UiO-66 was synthesized and evaluated as solid-phase extractor support for cadmium preconcentration in a micro-flow injection system coupled to thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) detection. The adsorbent was characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, and textural data from N2 adsorption/desorption isotherm data. The optimized conditions were achieved by loading 10.0 mL of a sample, containing 0.05 mol L-1 of phosphate buffer solution at pH 8.0, at a high flow rate of 10.0 mL-1 through 20.0 mg of UiO-66 packed into a mini-column, followed by elution with 1.0 mol L-1 HCl. At these conditions, the method presented a preconcentration factor of 35.7, limit of detection of 0.03 μg L-1 and a dynamic linear range from 0.1 to 8.0 μg L-1. The adsorption performance of UiO-66 towards cadmium was not influenced by Pb2+, Hg2+, Fe2+, Co2+, Cu2+, Ni2+, Zn2+, Mg2+ and Ca2+ ions. Analysis of different waters samples (tap water, physiological solution, mineral water, and lake water) was carried out without matrix interference, yielding recovery values ranging from 92.0 to 111.9%.