A magnet-renewable electroanalysis strategy for hydrogen sulfide in aquaculture freshwater using magnetic silver metal-organic frameworks.

A magnet-renewable electroanalytical strategy has been initially developed for monitoring hydrogen sulfide (H2S) in aquaculture freshwater systems using magnetic Fe3O4-loaded silver metal-organic framework (Fe3O4@Ag-MOF). The magnetic composites were synthesized by a hydrothermal route and further attached onto the magnetic electrodes. It was discovered that the Fe3O4@Ag-MOF-based electrochemical sensors could exhibit the extremely sharp and steady signals of solid-state Ag/AgCl electrochemistry at a lower potential. Furthermore, the highly specific and irreversible S-Cl replacement reactions could occur in the presence of H2S, so as to induce the conversion of AgCl into non-electroactive Ag2S with the rational decline of Ag/AgCl signals. Importantly, the Fe3O4@Ag-MOF-modified electrodes could be renewed simply by the removal of the magnet after each of the detection cycles for the next immobilization of Fe3O4@Ag-MOF probes. The developed electroanalytical method could facilitate the detection of H2S in the linear range from 4.0 to 1400 nM, with a limit of detection down to 2.0 nM. Besides, it was employed to detect H2S in aquaculture freshwater samples of fish, crab, and shrimp, showing the satisfactory results.