A sensitive and selective method for visual chronometric detection of copper(II) ions using clock reaction

Abstract

We report a visual chronometric method for the detection of copper(II) ions (Cu 2+ ) using the clock reaction between methylene blue (MB) and hydrazine (N 2 H 4 ). The addition of Cu 2+ greatly accelerates the clock reaction due to the formation of the Cu cluster between Cu 2+ and N 2 H 4 . By recording the change of the reaction time and solution color, different concentrations of Cu 2+ in buffer and environmental water have been detected. As low as 300 nM Cu 2+ can be visually identified by the naked eye without the assistance of any advanced instruments. This visual chronometric assay shows a dynamic range from 0.2 to 16 μM with a limit of detection of 20 nM. Additionally, it has good selectivity toward Cu 2+ and against other common metal cations.