A 2,4-dinitrophenylhydrazine/kojic acid derivative as a simple colorimetric probe for determination of cupric ions in water

We herein introduce a new simple colorimetric probe for sensitive and selective detection of cupric ions (Cu2+) at trace level. A derivative of 2,4-dinitrophenyl-hydrazine and kojic acid was successfully synthesized, and its use as a colorimetric probe for the determination of Cu2+ ions in water was evaluated. This probe binds Cu2+ ions in a 1:1 manner, changing color from yellow to colorless, with a decrease in the absorbance of the chromophore at 360 nm. The probe is selective for Cu2+ ions: no other metal ions induced a response, even at high concentration. The response to Cu2+ ions was linear with a detection limit of 0.85 μM, much lower than the maximum level permitted in drinking water (20 μM) by the US Environmental Protection Agency. This probe was subsequently applied to the determination of cupric ions in tap and lake water, good recoveries and reproducibility (RSD < 5%) were revealed.