Bifunctional Single Cobalt Site Catalyst-Enhanced Photochemical Vapor Generation for Determination of Bismuth by Atomic Fluorescence Spectrometry

Atomic fluorescence spectrometry (AFS) has become a widely used method for determining inorganic elements. However, improving the sensitivity and selectivity of AFS detection for trace or ultratrace elements is a major bottleneck. In this work, a single cobalt site catalyst anchored on a ketoenamine-based covalent organic framework (Co-COF) was developed and first utilized as a simultaneous adsorbent and photocatalyst for the determination of Bi³⁺ by photochemical vapor generation-atomic fluorescence spectrometry (PVG-AFS). The interference from coexisting hydride-forming elements and transition metal ions was greatly reduced after the matrix separation with Co-COF. Under the selected experimental conditions, the analytical sensitivity for bismuth by PVG-AFS was largely improved, and the limit of detection (LOD) was reduced to 0.009 μg L⁻¹. The method accuracy was validated by successful determination of bismuth in natural water samples and soil-certified reference materials. This work unveils the great potential of single-atom catalysts in PVG and opens a new avenue for sample introduction in atomic spectrometry.