Transparent Polycaprolactam Electrospun Nanofibers Doped with 1,10-phenanthroline Optical Sensor for Colorimetric Determination of Iron (II) and Vitamin C

A novel optical chemical sensor based on a transparent electrospun nanofibrous scaffold, composed of polycaprolactam (PA6) and 1,10-phenanthroline (Phen), deposited on a glass slide and impregnated with polyvinyl alcohol (PVA) was coupled with UV-vis spectrophotometry and used for colorimetric determination of ferrous ion (Fe²⁺) and ascorbic acid (AA). The electrospun nanofibers were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) techniques. The main factors affecting performance of the optical sensor (PA6-Phen/PVA@glass) including Phen dosage, pH of sample solution, electrospinning time, polymer solution flowrate, electrospinning voltage, and PVA amount were investigated and the related optimum values were obtained. The analytical merits of the sensor for quantitative determination of Fe²⁺ and ascorbic acid was evaluated. The limit of detection (LOD) and limit of quantification (LOQ) for Fe²⁺ were 1 and 3 μg mL^-1, respectively. The linear dynamic range (LDR) was 3–150 μg mL^-1 with the determination coefficient (R²) of 0.991. The relative standard deviation (RSD %, n=3) for a solution of 60 μg mL^-1 was 5.4 %. For determination of AA, LOD and LOQ were obtained equal to 0.5 and 2 μg mL^-1, respectively. The linear dynamic range was in the 2–200 μg mL^-1 range with a R2 of 0.994. The RSD % at 100 μg mL^-1, n=3) was equal to 7.0 %. The sensor was applied successfully to the detection of Fe(II) and AA in real water samples and aspirin tablets.