Solid-Phase Fluorescence Filter Effect: Toward Field and Ultrasensitive Detection of Iodine Speciation in Seawater

On-siteanalysis of iodine and its speciation in seawater is importantfor the prediction of radioactive iodine contamination. However, currentmethods, both colorimetric and instrumental, cannot meet the recentdemand for field analysis and an increased reliability of results.Herein, a solid-phase fluorescence filter effect (SPFFE) induced byiodine was found and further used to develop a ratiometric fluorescencepaper analysis device (RFPAD) for the analysis of iodine and its speciationin seawater. The proposed SPFFE-based assay surpasses the sensitivityand interference limitations arising from a specific extinction coefficientand multiple absorbers during real sample analysis, yielding an ultralowlimit of detection of 550 pM for iodine. In conjunction with a smartphone,a developed program, and a sensing platform, both field-sensitivedetection and speciation analysis of iodine could be achieved. AnRFPAD was successfully used for the field speciation analysis of iodineand iodate in the South China Sea, showing excellent anti-interferencecapability and retaining promising potential for warning about radioactiveiodine contamination in the ocean.