A composite prepared from a metal-organic framework of type MIL-101(Fe) and morin-modified magnetite nanoparticles for extraction and speciation of vanadium(IV) and vanadium(V).

A novel magnetic metal-organic framework (MOF) consisting of MIL-101(Fe) and morin-modified magnetite nanoparticles was synthesized and utilized for the extractive speciation analysis of V(IV) and V(V) at trace levels. The magnetic MOF exhibits selectivity toward V(V) at pH = 5.8. The concentration of V(IV) can be determined after its oxidation to V(V) and extracting total vanadium. After sorption and elution steps, vanadium can be determined by ETAAS. Under the optimal conditions, the limit of detection, linearity and the relative standard deviation for V(V) are 3.0 ng L, 10-750 ng L and 6.0%, respectively. The new method was validated by employing two certified reference materials. Finally, the method was successfully utilized for fast and selective speciation analysis of V(IV) and V(V) in water and food samples. Graphical abstract A novel functionalized magnetic metal-organic framework was synthesized and used for the speciation and preconcentration of trace amounts of vanadium.