A novel sensing membrane for the determination of ferric ions in aqueous solutions

Abstract

A new fluorescent sensing membrane, in which a naphthalimide derivative containing two long hydrophobic hydrocarbon chains, amphiphilic molecule castor oil polyoxyethylene ether and PVC were respectively used as the fluorescent indicator, plasticizer and matrix, for specific recognition of Fe³⁺ was prepared based on the physical entrapment method. The results show that the fluorescence of the sensing membrane is selectively quenched by Fe³⁺ ions over other common metal ions in aqueous solutions. A good linear response range of the sensing membrane is achieved from 5.0 × 10⁻⁵ to 1.5 × 10⁻³ M (R² = 0.9906), with a detection limit of 4.0 × 10⁻⁷ M. The sensing membrane shows good reversibility, a fast response of less than 20 s and satisfactory stability with a relative standard deviation of ±1.5%. Moreover, it was successfully applied in the detection of Fe³⁺ in tap water with recovery in the range of 97.6–101.2%.