A selectively fluorescein-based colorimetric probe for detecting copper(II) ion

A novel fluorescein derivative furfuraldehyde fluorescein hydrazone (FFH) has been synthesized by reacting fluorescein hydrazide with furfuraldehyde and characterized by 1 H NMR, 13 C NMR, MS and elemental analysis. Addition of Cu 2+ to the solution of FFH results in a rapid color change from colorless to yellow together with an obvious new band appeared at 502   nm in the UV–vis absorption spectra. This change is attributed to the spirocycle form of FFH opened via coordination with Cu 2+ in a 1:1 stoichiometry and their association constant is determined as 6.1   ×   10 4   L   mol −1 . Experimental results indicate that the FFH can provide a rapid, selective and sensitive response to Cu 2+ with a linear dynamic range 6.6–330   μmol/L. Common interferent ions do not show any interference on the Cu 2+ determination. It is anticipated that FFH can be a good candidate probe and has potential application for Cu 2+ determination in aqueous solution.