Highly selective optical sensing of copper(ii) ions based on fluorescence quenching of immobilised Lucifer Yellow

Abstract

We describe the development of an optical sensing scheme for the determination of copper(II) in drinking or waste water. It is based on static quenching of the fluorescence of Lucifer Yellow immobilised on anion exchanger particles, embedded in a hydrogel. The sensing membrane allows the determination of copper(II) in the 0.01 μM (0.63 μg l⁻¹) to 100 μM (6300 μg l⁻¹) concentration range with an outstanding high selectivity. The change in fluorescence on exposure to a significant concentration of 31 μM (2000 μg l⁻¹) is −60%. The response time is concentration dependent and varies from 100 to 3 min. Selectivity was investigated by the separate solution method; mercury(II) was found to be the only interferent. The effect of pH was evaluated in the range 4.0–6.8. The application of the sensing membrane as a single shot test was demonstrated using microtitre plates for copper(II) determination in tap water samples.