A Highly Structured 1,10-Phenanthroline Arrayed Hydrophobic Sulfone Membrane Platform for the Rapid Determination and Speciation of Fe 2+ /Fe 3+ Ions in Water.

An optical assay for the rapid determination and chemical speciation of Fe2+ /Fe3+ species has been proposed for the first time on a polyether sulfone (PES) membrane platform. The small pore size and low wettability (θ ∼82°) of the membrane disallowed the dissipation of analyte droplets on the surface, thus localizing it onto nanoliter arrayed 1,10-phenanthroline spots. Under optimized conditions and within ∼5 min, an acceptable limit of detection (0.1 μg mL-1 ) and linear dynamic range (1 - 100 μg mL-1 ) were achieved. The proposed method was also successfully applied for indirect determination of Fe3+ ions in synthetic samples after reduction to Fe2+ using SO2 . The performance of the proposed sensor was validated for its robustness and stability. Due to high selectivity and accuracy, the method was satisfactorily applied for the analysis of Fe2+ /Fe3+ species in marine water samples. The proposed method is an easy and low-cost system coupled with good reproducibility and ruggedness, applicable for point-of-use testing.