摘要
Ferrous ion (Fe 2+ ) can indicate the redox situation of water and also plays an important role in maintaining the ecological balance of water bodies. However, due to the redox-active property of Fe 2+ , it is still a huge challenge to sensitively and accurately determine Fe 2+ especially in interstitial water. Herein, we prepared a ferrozine gel rod for valence fixation during sampling and subsequent smartphone-based detection of Fe 2+ . The electrode potential of the redox pair can be varied through the formation of Fe 2+ -ligand complexes, and when E complex was higher than E O 2 / OH − , the oxidation of Fe 2+ by O 2 was hindered, thus achieving the valence fixation of Fe 2+ . Six ligands were screened, and it was found that ferrozine could effectively increase the redox potential after complexing with Fe 2+ , and also exhibits an obvious color change while fixing the valence of Fe 2+ . To facilitate Fe 2+ detection, a cross-linked porous polymer gel rod prepared by acrylamide and sodium alginate was used to encapsulate the ferrozine molecules. The ferrozine gel rod enabled fixation the valence of Fe 2+ longer than 30 days, and the resulted purple-red color was pictured and analyzed by a smartphone. Ultimately, the developed ferrozine gel rod sensing system was able to achieve sensitive and linear detection of Fe 2+ in the range of 1–200 μM with the limit of detection as low as 0.33 μM, and it also exhibited excellent selectivity and anti-interference ability. The accuracy and reliability of the method was verified by the determination of Fe 2+ in spiked water samples and certified standard reference water samples. Finally, the ferrozine gel rod sensing system was successfully applied to in-situ detection of Fe 2+ in interstitial water, overlying water and upper water of lake and river. This facile system that enabled valence fixation and fast detection is promising for detection of Fe 2+ in environmental waters.
危险品化学品经营许可证（带存储）