Sensitive paper-based test strips for quantitative determination of iron (Fe2+) in foodstuffs using optimized colorimetric reagents.

A facile colorimetric paper-based test strip was developed for iron (Fe2+) measurement in foodstuffs. Three colorimetric reagents, o-phenanthroline, 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ), and 5-sulfosalicylic acid (SSA), were compared in terms of colorimetric spectra, sensitivity, and accuracy. All experimental conditions were optimized to achieve maximum color intensity. Test strips were fabricated using a straightforward and rapid stepwise immersion process, wherein reagents were sequentially applied to produce strips with a single detection pad specifically designed for iron detection. Structural characterization of the test strips was performed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that o-phenanthroline is the optimal reagent due to its high sensitivity, precision and stability, and wide linear range. The optimized test strips showed a detection limit of 1.26 mg/kg and quantification at 3.78 mg/kg within 30 s. The test strips quantified iron in food with high accuracy, showing strong promise for practical applications.