Development of a green polymer-based sensor for enhanced iron detection in diverse biological, food and environmental...

The determination of iron in fortified biological and foods samples is mandatory by many global regulatory agencies. A polymer inclusion membrane (PIM) composed of poly (vinyl chloride) (PVC) as the polymer matrix, dioctyl phthalate (DOP) serving as the plasticizer, and methyltrioctyl ammonium chloride (Aliquat 336) acting as the carrier, has proven effective for the preconcentration and analysis of iron. This method utilizes 2-(2-amino-3-hydroxypyridine-4-ylazo) benzoic acid (AHPAB) as a complexing agent, enabling a straightforward colorimetric detection process. Adjusting the chemical and physical factors influencing membrane efficiency expanded its practical applications. The Fe³⁺ transport remained consistent under the optimum conditions used in fabricating the PIM. Additionally, employing an acetate buffer at pH 3.66 as the stripping phase facilitated efficient Fe³⁺ transfer, even in the presence of significant competing anions within the analyzed samples. Total iron content was measured after an on-line oxidation process where Fe²⁺ was converted to Fe³⁺ using a hydrogen peroxide stream. The Fe²⁺ concentration was determined by subtracting the Fe³⁺ value from the total iron concentration. Mass calibration was achieved within the range compatible with ICP-AES. The detection limit, defined as 3σ_sβ/S, was 1.75 ng/mL. Repeatability, expressed as the relative standard deviation (RSD) from nine measurements at 60 ng/mL, was 1.75 %, while the inter-sensor repeatability across five chelating sensors was 2.5 %. Furthermore, highlight the potential advantages of incorporating AHPAB into PIMs, such as improved stability, reusability, and enhanced selectivity for Fe ions was achieved. The validated PIM-based method was effectively applied to analyze food, biological, and environmental samples containing naturally occurring Fe²⁺ ions.