Development of dispersive micro-solid phase extraction using QDs@ZIF-8 for the extraction of Ni(II) and Co(II) ions...

In this research, a hybrid sorbent known as QDs@ZIF-8, a composite of zeolitic imidazolate framework-8 and quantum dots, was synthesized and utilized for extracting Ni(II) and Co(II) ions from water and fruit juice samples. Due to its superior adsorption capacity, QDs@ZIF-8 was effectively implemented in dispersive micro-solid-phase extraction to extract Ni(II) and Co(II) ions. The structural and morphological characteristics of QDs@ZIF-8 were analyzed using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The sorbent containing the target metals was separated from the solution via centrifugation, followed by elution with diluted nitric acid solution to retrieve the heavy metal ions from the sorbent surface. The analytes collected in the desorbed solvent were then determined through flame atomic absorption spectrometry. The optimum extraction conditions were established as 12.5 mg of QDs@ZIF-8, pH 5, 250 µL of HNO₃ (5%, v/v) as the desorption solvent, 6 min of extraction time, and 4 min of desorption time. The developed method displayed exceptional analytical performance, with limits of detection determined to be 0.28 and 0.10 µg L^-1, and limits of quantification of 0.80 and 0.30 µg L^-1, for Ni(II) and Co(II) ions, respectively. Additionally, it showed wide linear ranges of the calibration curves in the ranges of 0.80-100 µg L^-1 for Ni(II) and 0.30-100 µg L^-1 for Co(II), along with good repeatability, as indicated by relative standard deviation values of 3.3 and 2.8%, respectively. Furthermore, the method was successfully employed to measure Ni(II) and Co(II) ion concentrations in different water and fruit juice samples, underscoring its applicability for environmental analysis.