Ultrasensitive and specific fluorescent probe towards sulfites to monitor its residue in the traditional herbs.

As one of the traditional pretreatments for many Chinese herbal medicines, Sulfur Fumigation might remain residual sulfites which would endanger human health when overdosage. It should be invaluable to monitor their residual content in food or medicines. Abundant novel fluorescent probes for sulfur dioxide were designed, constructed and evaluated with excellent sensitivity, but lack in specificity. One of numerous potential candidates based on semi-cyanine fluorophores, N-3-I was synthesized, characterized and identified as the satisfactory candidates for the rapid detection of sulfites (<1 min) in aqueous solution, high sensitivity (limit of detection at 4.54 nM, Na2SO3), excellent specificity (only towards sulfites) and satisfactory fluorescence variation (>500-fold, λmax = 488 nm, ex. 414 nm). Furthermore, the assay based on N-3-I was established and could quantitatively assess the accurate content of sulfites in the actual sample after optimization with the advantages of short time, less sample material required, low cost and high accuracy, which was comparable with standard method in the rapid detection of wine and solid samples, such as Chinese traditional herbs. The probe demonstrates a high potential for the accurate and rapid detection of sulfur dioxide in the real samples to assure the food safety.