Dual-mode colorimetric/fluorometric test paper for rapid on-site sulfur dioxide quantification in food and environmental samples

The utilization of sulfur dioxide (SO2) in food processing and industrial applications presents significant hazards to public health and environmental stability. To address the critical need for rapid and user-friendly SO2 detection methods, we present the design and synthesis of a novel probe, TN , for sensitive and selective quantification of SO2 in food and environmental water. Formulated with triphenylamine and nitroisoxazole as fundamental constituents, TN exhibits a unique response to SO2 within a remarkably brief 40-second timeframe. Upon specific Michael addition with SO2, TN undergoes a dramatic colorimetric transition from crimson to colorless, coupled with a pronounced blue shift in fluorescence emission from 570 nm to 475 nm. Leveraging these properties, we developed a portable TN-based visual detection test paper, enabling dual-mode colorimetric/fluorometric analysis for on-site SO2 quantification in diverse matrices. This innovative approach, facilitated by smartphone technology, offers a detection range of 0-80 mu M under ambient light and 0-100 mu M under UV excitation, making it the first reported method to fully cover the World Health Organization specified range (63.16 mu M). This study underscores the potential application of portable detection technology for SO2 in everyday households.