Bisulfite (HSO3−) is widely used as a preservative and antioxidant in the food industry and chemical manufacturing, yet its excessive residues pose risks to food quality, environmental safety, and human health. To achieve rapid, selective, and quantitative detection of HSO3−, a ratiometric fluorescent probe based on a benzothiazole–carbazole unit and a benzoindole ion was developed. Upon reaction with HSO3−, the probe exhibits a distinct dual-emission response, fluorescence intensity decreases at 612 nm and increases at 467 nm, enabling robust ratiometric sensing (F467/F612). Owing to its pronounced fluorescence modulation (emission signal change > 145 nm) and high sensitivity (limit of detection = 0.62 μM), the probe demonstrates reliable performance in aqueous samples and has been successfully integrated into portable test strips and swabs. Furthermore, when coupled with a smartphone-based colorimetric application software, the probe allows convenient and real-time quantification of both gaseous SO2 and aqueous HSO3− across environmental and food-related matrices. This work thus delivers a practical, instrument-free platform for sulfite monitoring in complex real-world settings.
Chunling Zhou, Yanxin Zhang, Ying Sun et al.· Methods and Applications in...· 0 citations
Sulfites are widely used as preservatives and antioxidants in food, but excessive intake poses health risks. Therefore, rapid, sensitive, and on‑site detection of sulfites is essential for food safety. In this work, a cationic small‑molecule fluorescent probe was synthesized via the condensation of
N
‑ethylcarbazole (electron donor) and a benzoindolium ion (electron acceptor). It exhibits a D–π–A architecture with an intramolecular charge transfer (ICT) effect, showing red fluorescence at 617 nm. Upon reaction with HSO
3
−
through Michael addition at the conjugated C═C bond, the ICT pathway is blocked, leading to fluorescence quenching. The probe displays excellent selectivity for HSO
3
−
(limit of detection = 0.1 µM). Significantly, it can be simply deposited onto filter paper to fabricate easy‐to‐use test strips. Under a 365 nm UV lamp, the test strips exhibit a visible color change from red to blue with increasing HSO
3
−
concentration, allowing naked‑eye detection. Coupled with a smartphone color‑reading application, a linear relationship between the blue‐to‐red intensity ratio (B/R) and HSO
3
−
concentration enables rapid on‑site quantitative analysis. The test strips were successfully applied to detect residual HSO
3
−
in various dried fruit samples. This work provides a simple, low‑cost, and practical method for detecting sulfite levels in food and environmental samples.
Kanli Wang, Chenle Liao, Qian Cao et al.· ChemistrySelect· 0 citations
