**7. References**


It was shown that the electrochemical reduction of nitric oxide in an atmosphere containing excess oxygen is not effective due to the low selectivity of the cathode materials. To solve the problem of effective electrochemical reduction of nitric oxide in the presence of the excess oxygen *S.Bredikhin et al.* (Awano et al., 2004b; Bredikhin et al., 2001a, 2001b) proposed the concept of artificially designed multilayer structure which should operate as an electrode with high selectivity. Our investigations have shown that substitution of traditional cathodes by the multilayer electro-catalytic electrode with an electrochemically assembled nanostructure leads to a dramatic decrease in the value of the electrical power required for NO decomposition. It was shown that multilayer electro-catalytic electrode should consist at list from three main functional layers: Cathode; Electro-catalytic electrode; Covering layer, in order to operate as an electrode with high selectivity. In 2008 *K.Hamamoto et.al.* (Hamamoto et al., 2008) proposed to use an electrochemical reactor with fourth additional NOx adsorption layer. The values of current efficiency in such reactors increase up to 20% and the values of the NO/O2 selectivity up to 25. These results indicate that this new type of electro-catalytic reactor can be used for practical applications. From our point of view, such systems should substitute traditional catalytic systems for exhaust gas

Armor, J.N., "Catalytic reduction of nitrogen oxides with methane in the presence of excess

Aronin, A., Abrosimova, G., Bredikhin, S., Matsuda, K., Maeda, K. & Awano, M., "Structure

Awano, M., Bredikhin, S., Aronin, A., Abrosimova, G., Katayama, S. & Hiramatsu, T., "NOx

Awano, M., Fujishiro, Y., Hamamoto, K., Katayama, S. & Bredikhin, S., "Advances in nano-

Bredikhin, S., Abrosimova, G., Aronin, A. & Awano, M., "Electrochemical Cells with

Bredikhin, S., Abrosimova, G., Aronin, A., Hamamoto, K., Fujishiro, Y., Katayama, S. &

Bredikhin, S., Maeda, K. & Awano, M., "NO decomposition by an electrochemical cell with

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mixed oxide working electrode", *Solid State Ionics* 144, 1-9, (2001).

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decomposition by electrochemical reactor with electrochemically assembled

structured electrochemical reactors for NOx treatment in the presence of oxygen",

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Awano, M., "Pt-YSZ Cathode for Electrochemical Cells with Multilayer Functional

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multilayer electrode", *Solid State Ionics* 175, 605–608, (2004).

Baker, R.A. & Doerr, R.C., *Ind. Eng. Chem. Process Des. Dev.* 4 (1965), p. 188. Baker, R.A. & Doerr, R.C., *J. Air Pollut. Control Assoc.* 14 (1964), p. 409.

decomposition", *Journal of Ionics*, 7, 109-115, (2001).

*Society* 88, 5, 1180-1185, (2005).

Bosch, H. & Janssen, F., *Catalysis Today*, 2, 369 (1988).

**6. Conclusion** 

purification.

**7. References** 


**9** 

**Sequential Injection Anodic Stripping** 

**Inorganic Arsenic Speciation** 

Yolanda Castrillejo2 and José L.F.C. Lima3 *1Universidad Autónoma del Estado de Hidalgo* 

> *2Universidad de Valladolid 3Universidade do Porto*

> > *1Mexico 2Spain 3Portugal*

José A. Rodríguez1, Enrique Barrado2, Marisol Vega2,

**Voltammetry at Tubular Gold Electrodes for** 

Arsenic is one of the most feared contaminants because of its high toxicity at low concentrations. Exposure to high levels of arsenic can cause problems in humans ranging from gastrointestinal symptoms to arsenicosis. Once this element is dissolved in water and is ingested, it is accumulated in the body. Contamination of groundwater with arsenic is one of the major environmental and public health problems on a global scale (NRC, 1999).

The World Health Organization guideline has established a concentration of 10 µg l-1 as the maximum residue limit for arsenic in drinking water (WHO, 2004). Well-known arsenic contaminated regions include Bangladesh, India and other countries. In Mexico, sources of drinking water exceeding 10 µg l-1 have been found in Baja California Sur, Chihuahua, Coahuila, Durango, Zacatecas, Hidalgo, Morelos, Guanajuato, Sonora and San Luis Potosí (Camacho et al., 2011). In Spain, the presence of naturally occurring arsenic in groundwater has been reported in the sedimentary Duero and Tajo Cenozoic basins, located in central

Arsenic is usually distributed as water soluble species, colloids, suspended forms and sedimentary phases. Mobilized arsenic is most likely transported by water and accumulated in downstream river sediments as a result of the great affinity of arsenic to iron rich phases. The most common sources of non-naturally arsenic worldwide arise from the presence of alloys used in manufacture of transistors, laser, semi-conductors and mining industry

There are more than 20 arsenic compounds identified in environmental and biological systems (Gong et al., 2002). The dominant forms of arsenic present in the environment are As(III) (arsenite) and As(V) (arsenate) (Mondal, 2006). As(III) binds to sulfhydryl groups impairing the function of many proteins and affects respiration by binding to the vicinal thiols in pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase. As(V) is a molecular

Spain (García-Sánchez et al., 2005; Gómez et al., 2006; Vega et al., 2008) .

**1. Introduction** 

(Smedley & Kinniburgh, 2002).

