Enhanced vitamin B12 detection using a CxNixOyFeyOx+3 bimetal-organic framework: A comprehensive electrochemical study

Abstract

The functions of neurons and blood cells are aided by vitamin B₁₂. Serum vitamin B₁₂ levels are picomolar, and their deficiencies may be remedied using vitamin B₁₂ tablets. Consequently, sensitive and selective vitamin B₁₂ detectors that can be used at the point-of-care for food, pharmaceutical, and biological samples are urgently needed. In this study, we present the synthesis and carbonization of a Ni- and Fe-based bimetallic organic framework for the electrochemical sensing of vitamin B₁₂. The crystalline nature and functional groups of the material were analyzed using X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, and the oxidation states within the framework were determined using X-ray photoelectron analysis (XPS). Field-emission scanning electron microscopy (FE-SEM) revealed a uniform spherical morphology with particle sizes ranging from 2 to 10 nm. Electrochemical analysis was performed to detect vitamin B₁₂ by cyclic voltammetry (CV) on a screen-printed carbon electrode modified with C_xNi_xO_yFe_yO_x+3. CV analysis revealed that the fabricated electrode exhibits excellent redox peaks at approximately 0.0245 and −0.514 V with a low detection limit of 49 nM for vitamin B₁₂ and a wide linear detection range up to 200 µM. Interference studies confirmed the selectivity of the sensor with minimal impact from common biomolecules and inorganic ions. The sensor demonstrated excellent repeatability (RDS = 3.5 %), reproducibility, and long-term stability, retaining 94 % of its initial current response for over 20 d. The real sample analysis of commercial vitamin B complex tablets demonstrated a recovery rate of 98.59 %, highlighting the practical applicability of the sensor in pharmaceutical analysis.