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Recently, Huang Xingji, researcher of Institute of Intelligent Machinery, Hefei Institute of Physical Science, Chinese Academy of Sciences, and Zhao Nanjing, researcher of Anhui Institute of Optics and Fine Mechanics, Hefei Institute of Physical Science, combined the electrochemical method with laser-induced breakdown spectroscopy (LIBS) to realize micro-microscopy on rice. Contaminant Cd(II) No interference detection. The work has important scientific significance in the use of optical-electrochemical methods to achieve accurate detection of heavy metal ions in complex samples. The relevant research results have been published in the Electrochemical Journal of the Engineering Technology Journal (Electrochimica Acta 2016, DOI:http: //dx.doi.org/doi:10.1016/j.electacta.2016.09.016).
In recent years, the issue of rice safety has attracted much attention. In the Chinese market, about 10% of rice has the problem of Cd(II) pollution. Taking into account the high risk of Cd(II) to human health, accurate detection of Cd(II) in rice is crucial to safeguarding rice safety. However, the composition of rice is complex and diverse, and the content of some coexisting ions is even several hundred times that of Cd(II). How to realize the detection of Cd(II) in rice without interference is currently a problem that researchers need to overcome. In traditional detection methods, electrochemical methods can be used for the detection of Cd(II) in rice, but these works cannot overcome the interference from coexisting ions Cu(II) and Mn(II). Therefore, the research institutes of the Smart Institute and the Anguang Institute are working together to make use of the new detection platform to improve the accuracy and selectivity of Cd(II) detection in rice.
The researchers realized the non-interference detection of trace Cd(II) in rice by combining electrochemical methods with LIBS. Firstly, the electrochemical method was used to enrich Cd(II) in the rice digestion solution in the form of Cd(0) on the surface of the working electrode. Then the quantitative analysis was performed on the Cd(0) on the working electrode using LIBS to obtain the final Cd in rice. (II) content. In this method, graphene oxide (GO) is modified on the surface of the working electrode by means of layer assembly to increase the efficiency of Cd(II) electro-enrichment. Under the weak acid condition of pH = 6.0, the deprotonation of the carboxyl group (COOH) on the surface of GO forms COO-, which makes the GO surface negatively charged. In the electrochemical enrichment process, a negative voltage applied to the working electrode forms a negative electric field around the electrode, and Cd(II) is transferred from the solution to the working electrode under the driving of the electric field, and is adsorbed on the GO surface by electrostatic attraction. These Cd(II)s were then reduced to Cd(0) immobilized on the surface of the working electrode.
The components of the rice digestion solution are complex and diverse, including Ca(II), Cu(II), Mg(II), Mn(II), Na(I), Zn(II), Ni(II) and K(I). The interference experiment results show that these ions have no significant effect on the LIBS detection of Cd(II). In addition, the electrochemical method combined with LIBS reduces the detection limit of the traditional LIBS method by 3 orders of magnitude, and increases the sensitivity by nearly 3 orders of magnitude. The research results provide new ideas for improving the detection performance of traditional LIBS, as well as for the accurate detection of trace inorganic pollutants in complex environmental samples.
The research work was supported by the National Major Scientific Research Project and the National Natural Science Foundation.
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