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.