Point‐of‐Care Photoresistive and Colorimetric Sensor for Iron Detection in Environmental and Biological Samples with Spectroscopic Validation

The development of an innovative, selective, and portable digital photoresistive sensor for sensing iron in the environment and biological samples is reported in this article. Colorimetric sensing of the analyte is investigated, akin to the spectrophotometric absorption principle. Iron in the sample is measured by the formation of orange-colored ferroin resulting from the 1,10-phenanthroline reaction. The reaction scheme is designed to be pH-specific, simple, quick, and effective in detecting trace amounts of iron in real sample matrices without employing any tedious route of synthesis and its characterization. A digital photoresistive prototype is fabricated using a light-emitting diode (LED) and a light-dependent resistor (LDR) to measure the concentration of iron much less than the recommended value by the World Health Organization (WHO). The limit of detection (LOD) is reported to be 0.017 mg L^-1, the lowest to date for the class of point of care (POC) devices. The sensor was tested on 55 real-life samples and exhibited good accuracy with UV-vis and AAS measurements with an average absolute % error of 3.258%-14.34%. The present prototype promises to be a user-friendly, cost-effective solution to the pressing need of monitoring iron for the environment and healthcare sector.