Chinese researchers found new interference mechanism in the simultaneous detection of heavy metal ions (HMIs) Cd(II) and Cu(II), providing new physical insights for the co-deposition of multiple HMIs and applicable guidance for the design of detection electrode.

This work was done by scientists in Institute of Intelligent Machines, Hefei Institutes of Physical Science. The results were published in Analytical Chemistry.

Striping voltammetry is a rapid and portable technique for detecting HMIs in the aqueous solution. However, in the solution containing more than one HMI analytes, the co-existed HMIs cause interference and the measurement accuracy cannot be guaranteed, which prevents the development of HMI detection in the fields of both fundamental research and industrial application.

In this work, the interference between two example HMIs, Cd(II) and Cu(II), was explored.

The team built a kinetic model to describe the electroanalysis of HMI and measured the key parameters through experiment.

By comparing the electrode kinetics of Cd and Cu in the individual detections and the simultaneous detections, scientists found that the replacement of Cd by Cu(II) at the preconcentration stage was the main reason for the interference and selecting the electrode material of Cu-affinity might be helpful to avoid such interference.

In addition, the interference between Cd and Cu was explained and the kinetic model could be applied to understand the electroanalysis for other HMIs.

This work was supported financially by the National Natural Science Foundation of China, the Postdoctoral Innovation Talents Supporting Project, the Science and Technology Major Project of Anhui Province, Key Program of 13th five-year plan, Hefei Institutes of Physical Science, Chinese Academy of Sciences (CAS).

Fig. (a) Illustration of the manual interference of Cd(II) and Cu(II) in the co-deposition; (b) Stripping voltammograms measured in the individual Cd(II) solution (blue line), the individual Cu(II) solution (red line), and the mixed solution of Cd(II) and Cu(II) (purple line); (c) Experiment (solid lines) and simulation (dashed lines) of the stripping voltammograms in the mixed solution of Cd(II) and Cu(II) under various square wave frequency; (d) SEM image of co-deposited Cd and Cu, where the blue line outlines a butterfly-shape Cd deposit. (Image by LIN Chuhong)