Pollution of As(III) in drinking water has currently raised worldwide concerns of public security due to its notorious toxicity. Among the conventional techniques, electrochemical method is available to detect trace As in water generally. However, the method when used in “unknown” natural water in which some other metal cations coexisted, problem of difficult quantification occurs. So it is very important to find an efficient system to improve selectivity and accuracy of arsenic determination.

Recently, A study team led by Prof. HUANG Xingjiu and Prof. LIU Jinhuai from Institute of Intelligent of Machines, Chinese Academy of Sciences (IIM) made breakthough in determination of tracing As(III) by using electro-adsorption combined X ray fluorescence.

The study team proposed an analytical technique which is based on electro-adsorption and X-ray fluorescence (XRF) for the quantitative and selective determination of As(III) in aqueous solution with ppb-level limits of detection (LOD) This approach uses electro-adsorption to enhance sensitivity and selectivity of arsenic XRF analysis. In electro-adsorption procedure, As(III) could be oxidized to H2AsO4- by a positive electricity field around adsorbents (NH2-CMSs). Meanwhile, positive charges existed on the NH2-CMSs modified tap surface provided a driving force for the transfer of H2AsO4-, which were electro-attracted from the solution onto adsorbents. Then, H2AsO4- was fixed onto the surface of NH2-CMSs by ionic attraction. Afterwards, the adsorbents with adsorbed H2AsO4- were characterized through using XRF analysis after dried in the air. It is worthy of mentioning that positive electricity field around adsorbents in electro-adsorption experiments can repel the metal cations nearby the adsorbents to solution, so interference from other metal ions can be ignored in determination of As(III).

This work is supported by the National Basic Research Program of China, the National High Technology Research and Development Program of China (863 Program), and the National Natural Science Foundation of China. More details of study results have been published in Analytical Chemistry, entitled Electroadsorption-Assisted Direct Determination of Trace Arsenic without Interference Using Transmission X ray Fluorescence Spectroscopy.

Experimental setup for electro-adsorption assisted direct determination of As(III) using transmission X-ray fluorenscence spectroscopy. Conductive tap modified with NH2-CMSs are used as solid substrate for electro-adsorption of arsenic. Such a substrate concentrated with arsenic is directly for XRF measurement after drying. (Imaged by JIANG Tian Jia )

Contact:

Prof. Xing-Jiu HUANG, Ph. D

Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031, China

Tel: 86-551-6559-1167

Email: xingjiuhuang@iim.ac.cn (X.J.H)