Development of an iodine sensor based on fluorescence energy transfer

Abstract

A new optical chemical sensor for the determination of iodine based on fluorescence energy transfer between anthracene (donor) and 5,10,15,20-tetraphenylporphyrin (TPP), (acceptor) was developed. When incorporated in a membrane composed of plasticized poly(vinyl chloride) (PVC), anthracene transfers its emission energy to TPP, which then emits fluorescence according to its own characteristic fluorescence spectrum. The fluorescence of anthracene is strongly quenched by iodine, but that of TPP only weakly. When the PVC membrane containing these two types of fluorescence contacts a solution of iodine, stronger fluorescence quenching of TPP occurs. With the optimum membrane described, iodine in a sample solution can be determined from 1.0 × 10⁻⁶ to 2.5 × 10⁻⁴ mol l⁻¹. Satisfactory reproducibility, reversibility and a short response time of less than 1 min are realized. The sensor also shows good selectivity; common ions in foodstuffs do not interfere. The proposed method was applied to the determination of iodine in table salt samples. The results agree with those obtained by other methods.