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

• A novel fluorescein derivative furfuraldehyde fluorescein hydrazone (FFH) was synthesized and characterized.
• FFH have a rapid, selective and sensitive response to Cu2+.
• FFH has good solubility in ethanol and aqueous solution media.
• FFH can be a good colorimetric probe for Cu2+ determination.

A novel fluorescein derivative furfuraldehyde fluorescein hydrazone (FFH) has been synthesized by reacting fluorescein hydrazide with furfuraldehyde and characterized by 1H NMR, 13C NMR, MS and elemental analysis. Addition of Cu2+ 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 Cu2+ in a 1:1 stoichiometry and their association constant is determined as 6.1 × 104 L mol−1. Experimental results indicate that the FFH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 6.6–330 μmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that FFH can be a good candidate probe and has potential application for Cu2+ determination in aqueous solution.

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