All-in-one detecting dairy iodine based on single drop microextraction coupled with ratiometric fluorescence filter effect

Accurately detecting iodine in dairy products is paramount to ensure adequate intake and prevent iodine excess or deficiency-related diseases. However, the development of rapid sample digestion-coupled portable sensitive assays represents a significant challenge in the home-based analysis of iodine content in dairy products. Herein, an integrated portable device was developed, which combines sample digestion, microextraction, and fluorescence signal reading. The system ensures highly sensitive detection with minimal matrix interference by utilizing a rapid thermal-assisted digestion technique with minimal sample volume (500 μL) and high-enrichment headspace single-drop microextraction. Under optimal conditions, the ratiometric fluorescence filter effect system, coupled with a smartphone, gives a detection limit of 7 nM for iodine. Moreover, the accuracy of the strategy is further validated by real sample analyses and standard method comparisons. This method provides a practical tool for monitoring dietary iodine intake, particularly infant nutrition.