Portable Sensing Platform for the Visual Detection of Iodide Ions in Food and Clinical Samples

The detection of iodide ions (I−), despite challenges due to low concentrations and potential masking, is crucial for studying physiological processes and diagnosing diseases. A colorimetric sensor was developed to improve I− ion monitoring and facilitate on-site detection based on filter paper, which is a cost-effective platform. The sensor observed color changes in response to the exposure of hydrogen peroxide (H2O2), 3,3′,5,5′-tetramethylbenzidine (TMB), from colorless to yellowish brown. The sensor demonstrated a detection limit of 0.125 × 10−6 M for I− ions in a relatively wide range of 0.01 to 15 × 10−6 M under optimized conditions including gel concentration, temperature, incubation time, TMB and H2O2 concentration, and pH. Furthermore, the proposed sensor was successfully employed in a variety of applications, such as biological (urine and blood serum), food (egg yolk and snacks), and environmental samples (tap water). The study established effective recoveries in complex media for visual on-site I− ion monitoring, indicating the developed assay as a potent, affordable, and practical platform.