A Double-layered Paper-based Analytical Device for Determination of Iron in Water Samples based on Standard Addition Method

A simple method for the determination of iron involved a novel paper-based analytical device (PAD) was developed. The PAD was composed of two layers. Each layer contained a circular hydrophilic reservoir (10 mm Ø) that was situated in a rectangular filter paper (25 Î 25 mm2). The hydrophobic area was created by painting the paper with a “waterproof” glue. The top and the bottom layers were assigned as “the filtration” and “the detection” platforms, respectively. The procedure was started by pipetting an aliquot of bathophenanthroline (Bphen) onto the hydrophilic zone of the bottom layer followed by spiking of standard solutions (0.1-0.5 mgL-1 Fe2+). The red complex was developed. Then, the top and the bottom layers were assembled by two-sided mounting tape. Later, a water sample was dropped onto the top layer, which removed (filtered) any suspended particles in the water sample. When the filtrate was exposed to the bottom layer, a further colored product formed. The bottom layer was removed and placed in a light-controlled box, and the optical image of the product was captured using a smartphone. Its intensity was evaluated through ImageJTM. Linear standard addition plots were obtained (r2 > 0.99). The PAD provided high precision (RSD < 6%) with good recovery (92.6-102%). It was applied to the analysis of drinking, tap, canal and river water samples without any prior filtration. The iron amounts were compared to the results obtained by the spectrophotometric method, and there was not significantly difference at 95% confidence (Paired-t test, n = 5 samples, tstat = 2.68, tcri = 2.78).