Preface

*Arsenic - Analytical and Toxicological Studies* is a compilation of five chapters focused on ar‐ senic occurrence and chemistry, methods for arsenic determination and removal, and arsen‐ ic toxicity and health risks.

The three chapters included in the first section introduce: (1) the most commonly used tech‐ niques for arsenic quantification and speciation, such as atomic absorption spectrometry, in‐ ductively coupled plasma-mass spectrometry, and inductively coupled plasma-emission spectrometry, among others, often conjugated with separation techniques such as high-per‐ formance liquid chromatography, and (2) the various procedures applied for arsenic separa‐ tion and removal, including ion exchange, sorption, coagulation and membrane technologies. The advantages and drawbacks of the methods for arsenic determination and removal are exhaustively described.

The two chapters contained in the second section provide important information about: (1) the mechanism of arsenic-induced toxicology, involving arsenic interaction with critical thi‐ ols in proteins, and (2) the health risks associated with exposure to arsenic. The two case studies presented (Guanajuato, Mexico, and Bihar, India) comment in detail on the adverse effects of exposure to arsenic in water.

The book offers a professional multifaceted vision of several problems related to arsenic de‐ termination and effects of arsenic exposure.

All the contributing authors are gratefully acknowledged for their time and effort.

**Prof. DSc. Eng. Margarita Stoytcheva and Prof. Dr. Eng. Roumen Zlatev** Universidad Autónoma de Baja California Mexicali, México

**Section 1**

**Arsenic Occurrence and Removal**

**Arsenic Occurrence and Removal**

**Chapter 1**

Provisional chapter

**Introductory Chapter: Arsenic**

Introductory Chapter: Arsenic

Margarita Stoytcheva and Roumen Zlatev

Margarita Stoytcheva and Roumen Zlatev

http://dx.doi.org/10.5772/intechopen.78399

occurring according to Eq. 1 are H2AsO3

<sup>H</sup>3AsO<sup>3</sup>! pKa¼9:<sup>2</sup>

H3AsO4! pKa¼2:<sup>2</sup>

<sup>2</sup>�, and AsO4

HAsO4

1. Arsenic occurrence

Additional information is available at the end of the chapter

intermediate properties between metals and non-metals.

H2AsO�

H2AsO�

2. Arsenic and its compound application and removal

a negative charge, forming successively several anions according to Eq. 2:

<sup>4</sup> <sup>þ</sup> <sup>H</sup><sup>þ</sup>! pKa¼6:<sup>94</sup>

Arsenic (As) is a chemical element the abundance of which in the continental crust of the Earth is given as 1.5–2 ppm. Most often arsenic appears in nature in the form of Fe, Co and Ni arsenides, arsenic sulfide, and native arsenic. It belongs to the metalloids, in spite that it shows

DOI: 10.5772/intechopen.78399

In general, arsenic forms soluble oxyanions with the predominant oxidation states +3 and +5, while the minor oxidation states are 0 and �3. The main form of As(III) is arsenite existing in solutions with pH between 5 and 9. H3AsO3 and the anions resulting from its dissociation

�, H2AsO3

<sup>3</sup> <sup>þ</sup> <sup>H</sup><sup>þ</sup>! pKa¼14:<sup>22</sup>HAsO<sup>2</sup>�

The main form of As(V) is H3AsO4. The anions resulting from its dissociation are H2AsO4

double bond. The H3AsO4 molecule easily loses hydrogen ions by dissociation remaining with

Elemental arsenic has a limited application mainly as lead and brass alloy's ingredient, but its compounds are widely used in the industry. The gallium arsenide (GaAs) is extensively used in the electronic industry for high-frequency integrated circuits, laser diodes, and Light Emission Diodes (LEDs); the arsenic oxide is used in glass production industry; the arsenic sulfides

<sup>2</sup>�, and AsO3

<sup>3</sup>�. The arsenates have high-ionization capacity due to the presence of the

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

HAsO<sup>2</sup>�

3�:

<sup>3</sup> <sup>þ</sup> <sup>H</sup><sup>þ</sup>! pKa¼19:<sup>22</sup>AsO<sup>3</sup>�

<sup>4</sup> <sup>þ</sup> <sup>H</sup><sup>þ</sup>! pKa¼11:<sup>3</sup>

AsO3�

<sup>3</sup> <sup>þ</sup> <sup>H</sup><sup>þ</sup> (1)

<sup>4</sup> <sup>þ</sup> <sup>H</sup><sup>þ</sup> (2)

� ,

Additional information is available at the end of the chapter

#### **Chapter 1** Provisional chapter

#### **Introductory Chapter: Arsenic** Introductory Chapter: Arsenic

Margarita Stoytcheva and Roumen Zlatev Margarita Stoytcheva and Roumen Zlatev

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78399
