Fluorescent sensor based on newly synthesized fluorescein octadecyl ether octadecyl ester (FODEE) for direct determination of phenols in aqueous solutions

Fluorescein octadecyl ether octadecyl ester (FODEE) was synthesized. It was a better fluorescein analogue than fluorescein octadecyl ester (FODE). A prominent fluorescence enhancement effect was observed when the compound in poly(vinyl chloride)(PVC) membrane was applied to carboxylic acid solutions, while an outstanding quenching effect was observed when the membrane was applied to phenol solutions. Based on the quenching effect of phenols on FODEE, a fluorescent sensor for direct determination of phenols in aqueous solutions was developed. This sensor showed reversible response in the concentration range from 1.0 × 10−6 to 1.0 × 10−1 mol dm−3 for the detection of p-cresol in Tris-HCl buffer at pH 7.0. It also showed fast response time (t90% less than 3 min.) when the sensor was applied to p-cresol solution at concentration levels of 3.0 × 10−4 and 1.0 × 10−3 mol dm−3 alternatively. A working principle was proposed and the responses of this sensor to various kinds of phenol were studied.