posted on 2024-01-03, 19:35authored bySherman Lesly Zambou Jiokeng, Tobie J. Matemb Ma Ntep, Marcus N. A. Fetzer, Till Strothmann, Cyrille G. Fotsop, Ignas Kenfack Tonle, Christoph Janiak
As the excessive presence of heavy metals in the environment
significantly
affects human health, it becomes necessary to develop efficient, selective,
and sensitive methods for their detection. In this study, a novel
electrochemical sensor for the detection of Pb2+ ions is
described. The proposed sensor is based on a glassy carbon electrode
(GCE) modified by a thin film of histidine-grafted metal–organic
framework (MOF-808-His). The MOF-808 was obtained solvothermally,
and then postsynthetically modified by substituting the coordinated
acetate with histidinate. By electrochemistry, the MOF-808-His-modified
GCE demonstrated high charge selectivity, while electrochemical impedance
spectroscopy (EIS) and kinetic studies gave a lower charge transfer
resistance (4196 Ω) and a better standard heterogeneous electron
transfer rate constant (1.80 × 10–5 cm s–1) on MOF-808-modified GCE. These results indicated
a swift and direct electron transfer rate from [Fe(CN)6]3–/4– to the electrode surface. Using square
wave anodic stripping voltammetry (SWASV), the rapid and highly sensitive
determination of Pb2+ was achieved on MOF-808-His-modified
GCE. By optimizing the accumulation-detection parameters including
pH of the detection medium, deposition time and potential, and concentration,
a remarkable limit of detection (LoD, based on a signal-to-noise ratio
of 3) of (1.12 × 10–10 ± 0.10 × 10–10) mol L–1 was obtained, with a
sensitivity of (9.6 ± 0.1) μA L μmol–1. After interference and stability studies, the MOF-808-His-modified
GCE was applied to the detection of Pb2+ in a tap water
sample with a concentration of 10 μmol L–1 Pb2+.