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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Water is one of the most precious and basic needs of life for all living beings, and a precious national asset. Without it, the existence of life cannot be imagined. Availability of pure water is decreasing day by day, and water scarcity has become a major problem that is faced by our society for the past few years. Hence, it is essential to find and disseminate the key solutions for water quality and scarcity issues. The inaccessibility and poor water quality continue to pose a major threat to human health worldwide. Around billions of people lacking to access drinkable water. The water contains the pathogenic impurities; which are responsible for water-borne diseases. The concept of water quality mainly depends on the chemical, physical, biological, and radiological measurement standards to evaluate the water quality and determine the concentration of all components, then compare the results of this concentration with the purpose for which this water is used. Therefore, awareness and a firm grounding in water science are the primary needs of readers, professionals, and researchers working in this research area. This book explores the basic concepts and applications of water science. It provides an in-depth look at water pollutants' classification, water recycling, qualitative and quantitative analysis, and efficient wastewater treatment methodologies. It also provides occurrence, human health risk assessment, strategies for removal of radionuclides and pharmaceuticals in aquatic systems. The book chapters are written by leading researchers throughout the world. This book is an invaluable guide to students, professors, scientists and R&D industrial specialists working in the field of environmental science, geoscience, water science, physics and chemistry.
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Table of Contents
Cover
Title Page
Copyright
Preface: Applied Water Science I-Fundamentals and Applications
1 Sorbent-Based Microextraction Techniques for the Analysis of Phthalic Acid Esters in Water Samples
1.1 Introduction
1.2 Solid-Phase Microextraction
1.3 Stir Bar Sorptive Extraction
1.4 Solid-Phase Extraction
1.5 Others Minor Sorbent-Based Microextraction Techniques
1.6 Conclusions
Acknowledgements
References
2 Occurrence, Human Health Risks, and Removal of Pharmaceuticals in Aqueous Systems: Current Knowledge and Future Perspectives
2.1 Introduction
2.2 Occurrence and Behavior of Pharmaceutics in Aquatic Systems
2.3 Human Health Risks and Their Mitigation
2.4 Knowledge Gaps and Future Research Directions
2.5 Summary, Conclusions, and Outlook
Author Contributions
References
3 Oil-Water Separations
3.1 Introduction
3.2 Sources and Composition
3.3 Common Oil-Water Separation Techniques
3.4 Oil-Water Separation Technologies
3.5 Separation of Oil/Water Utilizing Meshes
3.6 Separation of Oil-Water Mixture Using Bioinspired Surfaces
3.7 Conclusion
Acknowledgements
References
4 Microplastics Pollution
4.1 Introduction and General Considerations
4.2 Key Scientific Issues Concerning Water and Microplastics Pollution
4.3 Marine Microplastics: From the Anthropogenic Litter to the Plastisphere
4.4 Social and Human Perspectives: From Sustainable Development to Civil Science
4.5 Conclusions and Future Projections
References
5 Chloramines Formation, Toxicity, and Monitoring Methods in Aqueous Environments
5.1 Introduction
5.2 Inorganic Chloramines Formation and Toxicity
5.3 Analytical Methods for Inorganic Chloramines
5.4 Organic Chloramines Formation and Toxicity
5.5 Analytical Methods for Organic Chloramines
5.6 Conclusions
References
6 Clay-Based Adsorbents for the Analysis of Dye Pollutants
6.1 Introduction
6.2 Membrane Filtration
6.3 Chemical Treatment
6.4 Photo-Catalytic Oxidation
6.5 Conclusions
Acknowledgments
References
7 Biochar-Supported Materials for Wastewater Treatment
7.1 Introduction
7.2 Generalities of Biochar: Structure, Production, and Properties
7.3 Biochar-Supported Materials
7.4 Conclusion
References
8 Biological Swine Wastewater Treatment
8.1 Introduction
8.2 Swine Wastewater Characteristics
8.3 Microorganisms of Biological Swine Wastewater Treatment
8.4 Classification of Biological Swine Wastewater Treatment
8.5 Biological Processes For Swine Wastewater Treatment
8.6 Challenges and Future Prospects in Swine Wastewater Treatment
References
9 Determination of Heavy Metal Ions From Water
9.1 Introduction
9.2 Detection of Heavy Metal Ions
9.3 Conclusions
References
10 The Production and Role of Hydrogen-Rich Water in Medical Applications
10.1 Introduction
10.2 Functional Water
10.3 Reduced Water
10.4 Production of Hydrogen-Rich Water
10.5 Mechanism Hydrogen Molecules During Reactive Oxygen Species Scavenging
10.6 Hydrogen-Rich Water Effects on the Human Body
10.7 Other Effects of Hydrogenated Water
10.8 Applications of Hydrogen-Rich Water
10.9 Safety of Using Hydrogen-Rich Water
10.10 Concluding Remarks
References
11 Hydrosulphide Treatment
11.1 Introduction
11.2 Conclusions
References
12 Radionuclides: Availability, Effect, and Removal Techniques
12.1 Introduction
12.2 Existing Techniques and Materials Involved in Removal of Radionuclide
12.3 Summary of Various Nanomaterial and Efficiency of Water Treating Technology
12.4 Management of Radioactive Waste
12.5 Conclusion
References
13 Applications of Membrane Contactors for Water Treatment
13.1 Introduction
13.2 Characteristics of Membrane Contactors
13.3 Membrane Module Configurations
13.4 Mathematical Aspects of Membrane Contactors
13.5 Advantages and Limitations of Membrane Contactors
13.6 Membrane Contactors as Alternatives to Conventional Unit Operations
13.7 Applications
13.8 Conclusions and Future Prospects
References
14 Removal of Sulfates From Wastewater
14.1 Introduction
14.2 Effect of Sulfate Contamination on Human Health
14.3 Groundwater Distribution of Sulfate
14.4 Traditional Methods for Sulfate Removal
14.5 Modern Day’s Technique for Sulfate Removal
14.6 Conclusions and Future Perspective
Acknowledgements
References
15 Risk Assessment on Human Health With Effect of Heavy Metals
15.1 Introduction
15.2 Toxic Effects Heavy Metals on Human Health
15.3 Biomarkers and Bio-Indicators for Evaluation of Heavy Metal Contamination
References
16 Water Quality Monitoring and Management: Importance, Applications, and Analysis
16.1 Qualitative Analysis: An Introduction to Basic Concept
16.2 Significant Applications of Qualitative Analysis
16.3 Qualitative Analysis of Water
16.4 Existing Water Quality Standards
16.5 Quality Assurance and Quality Control
16.6 Conclusions
References
17 Water Quality Standards
17.1 Introduction
17.2 Chemical Standards for Water Quality
17.3 Inorganic Substances and Their Effect on Palatability and Household Uses
17.4 The Philosophy of Setting Standards for Drinking Water (Proportions and Concentrations of Water Components)
17.5 Detection of Polychlorinated Biphenyls
17.6 The Future Development of Water Analysis
17.7 Conclusion
References
18 Qualitative and Quantitative Analysis of Water
18.1 Introduction
18.2 Sources of Water
18.3 Water Quality
18.4 Factors Affecting the Quality of Surface Water
18.5 Quantitative Analysis of the Organic Content of the Wastewater
18.6 Treatment of Wastewater
18.7 Instrumental Analysis of Wastewater Parameters
18.8 Methods for Qualitative Determination of Water
18.9 Conclusion
References
19 Nanofluids for Water Treatment
19.1 Introduction
19.2 Types of Nanofluids Used in the Treatment of Water
19.3 Conclusion and Recommendation to Knowledge
References
Index
End User License Agreement
Guide
Cover
Table of Contents
Title Page
Copyright
Preface: Applied Water Science I-Fundamentals and Applications
Begin Reading
Index
End User License Agreement
List of Illustrations
Chapter 1
Figure 1.1 The chemical structures of PAEs. Adapted from [1]. PAEs, phthalic aci...
Figure 1.2 DEHP biodegradation pathways to obtain MEHP, DBP, and DEP. Reprinted ...
Figure 1.3 Schematic representation of the SiO
2
-PDMS-MWNTs fiber preparation. Re...
Figure 1.4 Extraction yields with different fibers (MI-SPME, PDMS, CW/DVB, and P...
Figure 1.5 Scheme of a similar extraction procedure carried out by Chen
et al.
[...
Figure 1.6 Scanning electron microscope image (A) and transmission electron micr...
Figure 1.7 Schematic illustration of the preparation strategy for m-NPs and the ...
Chapter 2
Figure 2.1 Summary depiction of the nature, sources, behaviour, human exposure a...
Figure 2.2 Human exposure pathways to pharmaceuticals in the environment.
Chapter 3
Figure 3.1 Basic principle involved in the membrane technology [Permission taken...
Chapter 4
Figure 4.1 The marine microplastics sampling system.
Figure 4.2 The microplastics and no-polymer debris under an optical microscope; ...
Figure 4.3 The ubiquitous on the beach debris of microplastics—in the Mediterran...
Chapter 5
Figure 5.1 The pathway for the formation of inorganic chloramines during chloram...
Figure 5.2 Colorimetric methods and reagents for determination of chlorine and c...
Figure 5.3 Scheme of the device for TCA measurements with the extraction-based A...
Figure 5.4 The chemical probes used for precolumn derivatization of inorganic an...
Figure 5.5 Descriptive scheme of the multi-syringe chromatography manifold for t...
Figure 5.6 Illustration for the MIMS process.
Figure 5.7 Pathways for the reaction of aldehydes and inorganic MCA, adapted fro...
Figure 5.8 Pathway for the generation of N-chloraldimine from N-chloroamino acid...
Figure 5.9 Fluorescence determination of the organic chloramine (TCCA).
Chapter 6
Figure 6.1 Classification of clay minerals.
Figure 6.2 Chemical structure of kaolinite clay [16] adapted with permission fro...
Figure 6.3 The formation process of chitosan/organic rectorite-Fe
3
O
4
microsphere...
Chapter 7
Figure 7.1 Effect of pyrolysis temperature on biochar structure.
Figure 7.2 X-ray diffractogram of (a) wood and (b) grass biochars generated at t...
Figure 7.3 Thermochemical conversion technologies for biomass.
Figure 7.4 SEM images of Douglas fir wood (a), Douglas fir bark (b), and hybrid ...
Figure 7.5 Different functional groups present on the surface of biochar prepari...
Figure 7.6 FTIR-ATR spectra of biomasses and their respective biochars produced ...
Figure 7.7 van Krevelen diagram of different biochars produced from a wide range...
Figure 7.8 Novel magnetic biochar material derived from waste banana pseudo stem...
Figure 7.9 Structural characteristics of biochar-graphene nanosheet composites a...
Figure 7.10 SEM images of BC (A), MgFe
2
O
4
(B), MgFe
2
O
4
-BC (C), BM-La(b) (D), MgF...
Figure 7.11 Photocatalytic mechanism scheme and charge transfer of the biochar@ ...
Figure 7.12 Sorption mechanisms for biochar-supported materials contaminants upt...
Chapter 8
Figure 8.1 Metabolic pathways according to the availability and utilization of o...
Chapter 9
Figure 9.1 Functioning of a biosensor [25].
Figure 9.2 Representation of SPR sensor.
Chapter 10
Figure 10.1 Schematic diagram showing all the active species responsible for sca...
Figure 10.2 Multifunctional activity of ROS-scavenging in Pt nanoparticles [8]. ...
Figure 10.3 Correlation between time and the hydrogen content of three different...
Figure 10.4 Diagram showing the comparable increase of TH-positive neurons at 0....
Figure 10.5 Decrease in serum histamine for the mice were given hydrogen-rich wa...
Figure 10.6 Changes in rat body weight after 30 Gy local head and neck radiation...
Figure 10.7 Photographs and percentages showing the healing of mice palatal woun...
Figure 10.8 A schematic diagram showing the setup of the hemodialysis system tha...
Figure 10.9 A summary of the positive health effects of hydrogen-rich water [8].
Chapter 11
Figure 11.1 Enzymatic biosynthesis pathway of H
2
S in vital cell. 3-MST, 3-mercap...
Figure 11.2 Nonenzymatic biosynthesis pathway of H
2
S in vital cell. Modified aft...
Figure 11.3 The important roles of H
2
S to improve plant tolerance against variou...
Figure 11.4 Some metabolic and signaling routes against salinity stress. ABA, ab...
Figure 11.5 (a) Effect of NaHS treatment on the sprouting of wheat under normal ...
Figure 11.6 H
2
S defense mechanism to ameliorate plant tolerance under various st...
Figure 11.7 Summary of obtained results about the effects of NaHS treatment on t...
Figure 11.8 Removal efficiency for 100 mg/L of various heavy metals by Phaneroch...
Figure 11.9 Superoxide dismutase (a) and catalase (b) activity for NaHS treatmen...
Figure 11.10 Comparison of NaHS and some salts (containing sodium and sulfide co...
Figure 11.11 Arsenic removal efficiency by enargite leaching with NaHS-NaOH solu...
Figure 11.12 Effect of NaHS level on copper precipitation efficiency at 20°C and...
Chapter 12
Figure 12.1 Natural radiation exposure [11].
Figure 12.2 Significant radionuclides in water supply [18].
Chapter 14
Figure 14.1 Design of limestone bed treatment plant.
Chapter 15
Figure 15.1 Sources and pathways of heavy metals in environment [5].
Figure 15.2 Effect of heavy metals on human being [11].
Chapter 18
Figure 18.1 (a-c) Represents the availability and type of water on earth crust.
Figure 18.2 Variation in DO profile during BOD test with duration of incubation.
Figure 18.3 Oxygen demand for nitrification in BOD test.
Figure 18.4 Correlation between BOD and COD for sewage at 20°C.
Figure 18.5 Schematic diagram of the wastewater treatment plant.
Figure 18.6 Processes involved in waste water treatment.
Figure 18.7 Flowchart showing the reactions pathway involved in an anaerobic dig...
Figure 18.8 Conventional activated sludge process.
Figure 18.9 Spray tower.
List of Tables
Chapter 1
Table 1.1 Some examples of the application of SPME and SBSE for the analysis of ...
Table 1.2 Some examples of the application of SPE for the analysis of PAEs in wa...
Table 1.3 Some examples of the application of other sorbent-based extraction tec...
Chapter 2
Table 2.1 Human exposure assessment and health risk assessment for pharmaceutica...
Chapter 3
Table 3.1 The functions of individual chambers are as follows.
Table 3.2 Physical and chemical method of oil-water separation [Permission taken...
Table 3.3 Typical filtration-based oil/water separation materials fabricated by ...
Chapter 6
Table 6.1 Dye removal capacities of raw and modified clays.
Table 6.2 Removal of dyes using clay-modified catalysts via Fenton process under...
Chapter 7
Table 7.1 The difference between the three types of pyrolysis process.
Chapter 8
Table 8.1 Concentrations of pollutants in swine wastewater.
Table 8.2 Common microorganisms encountered in biological wastewater treatment.
Chapter 11
Table 11.1 Influence of NaHS treatment on the sprouting and growing of wheat wit...
Table 11.2 Influence of NaHS treatment on sprouting and growing of wheat under 0...
Table 11.3 Summary of some studies about the effects of pretreatment of seeds wi...
Table 11.4 Researches emphasizing the essential role of H,S in erection response...
Table 11.5 Summary of several researches for H2S treatment and its level to impr...
Table 11.6 The precipitation efficiency of copper and arsenic during enargite le...
Table 11.7 The effect of NaHS concentration on the recovery efficiency for chalc...
Chapter 12
Table 12.1 Natural isotopes of uranium and their characteristics are illustrated...
Table 12.2 Natural isotopes of uranium and their characteristics are illustrated...
Table 12.3 Radium natural isotopes and their characteristics are demonstrated as...
Table 12.4 Radon natural isotopes and their characteristics are demonstrated as ...
Table 12.5 Merits and demerits of various nanomaterials [90].
Table 12.6 Efficiency of various water treating technologies [18].
Chapter 15
Table 15.1 Metal/metalloids contamination in soils usual origination and geochem...
Table 15.2 Parameters of risk assessment with standard values [27].
Chapter 16
Table 16.1 Essential qualities of potable water.
Table 16.2 A comparative account of significant water quality index systems.
Table 16.3 Sample preservation criteria for water quality analysis.
Table 16.4 Drinking water quality standards for significant physico-chemical par...
Table 16.5 Requisites for analytical quality assurance.
Chapter 17
Table 17.1 The effective dose of the radioactive elements and the consumption fo...
Table 17.2 The salt taste of water.
Table 17.3 The salt taste of water and sodium salts.
Chapter 18
Table 18.1 Water consumption in various sectors.
Table 18.2 Criteria for the physical parameters.
Table 18.3 Criteria for the chemical parameters.
Table 18.4 Criteria for biological matters.
Table 18.5 Relative weight of chemical parameters.
Table 18.6 Classification of water quality on the bases of calculating WQI.
Table 18.7 Determination of the presence of alkalinity due to different combinat...
Table 18.8 Total organic carbon levels in various types of water.
Chapter 19
Table 19.1 Applications of nanofluids in water treatment.
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Applied Water Science Volume 1
Fundamentals and Applications
Edited by
Inamuddin,
Mohd Imran Ahamed,
Rajender Boddula,
and
Tauseef Ahmad Rangreez
This edition first published 2021 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA © 2021 Scrivener Publishing LLC
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Library of Congress Cataloging-in-Publication Data
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10 9 8 7 6 5 4 3 2 1
PrefaceApplied Water Science I-Fundamentals and Applications
Inamuddin1, Mohd Imran Ahamed2, Rajender Boddula3and Tauseef Ahmad Rangreez4
1Department of Applied Chemistry, Zakir Husain College of Engineering and Technology, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh, India
2Department of Chemistry, Faculty of Science, Aligarh Muslim University, Aligarh, India
3CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, China
4Department of Chemistry, National Institute of Technology, Srinagar, Jammu and Kashmir, India
Water is one of the precious and basic needs of life for all living beings and is a precious national asset. Without it, the existence of life cannot be imagined. Availability of pure water is decreasing day by day, and water scarcity has become a major problem that is faced by our society for the past few years. Hence, it is essential to find and disseminate the key solutions for water quality and scarcity issues. The inaccessibility and poor water quality continue to pose a major threat to human health worldwide. Around billions of people lacking to access drinkable water. The water contains the pathogenic impurities, which are responsible for water-borne diseases. The concept of water quality mainly depends on the chemical, physical, biological, and radiological measurement standards to evaluate the water quality and determine the concentration of all components and then to compare the results of this concentration with the purpose for which this water is used. Therefore, awareness and a firm grounding in water science are the primary needs of readers, professionals, and researchers working in this research area.
This book explores the basic concepts and applications of water science. It provides an in-depth look at water pollutants’ classification, water recycling, qualitative and quantitative analysis, and efficient wastewater treatment methodologies. It also provides occurrence, human health risk assessment, strategies for removal of radionuclides, and pharmaceuticals in aquatic systems. The book chapters are written by leading researchers throughout the world. This book is an invaluable guide to students, professors, scientists, and R&D industrial specialists working in the field of environmental science, geoscience, water science, physics, and chemistry.
Chapter 1 provides a general overview of different analytical methodologies that have been proposed for the analysis of phthalic acid esters in water samples. Special attention has been given to methods based on the application of sorbent-based microextraction techniques (i.e., solid-phase microextraction and micro solid-phase extraction magnetized or not, among others).
Chapter 2 discusses the occurrence, dissemination, and behavior of pharmaceuticals in aquatic environments. Human exposure pathways and health risks, including the emergence of antimicrobial resistance are summarized. Risk factors promoting human exposure in developing countries are discussed. Methods for removal of pharmaceuticals and future research directions are also highlighted.
Chapter 3 focuses on the latest developments in the methods for the oil/water separation through filtration of the membrane using distinct materials with surface properties that are super wetting.
Chapter 4 presents the fundamental studies on the interdisciplinary issue of microplastic-based pollution of water environments; the scientific approach and roadmap to this complex problem are discussed.
Chapter 5 summarizes the routes of formation of organic and inorganic chloramines upon chlorination disinfection. Chloramine’s possible health risks to humans including mutagenicity and hemolytic anemia are discussed. Further, the analytical methods for their control in aqueous environments are summarized. Selective methods including chromatographic and pH-controlled colorimetric techniques are highlighted.
Chapter 6 highlights the removal of industrial dyes using different approaches such as clay-based adsorbents, membrane filtration, and chemical treatment with special focus on clay-based low-cost adsorbents. The results of dyes’ adsorption study are discussed and compared with other reported wastewater treatment technologies.
Chapter 7 provides a general description of biochar material from the preparation (synthetic methods) to its application as a powerful adsorbent in the wastewater treatment field. Recent advancements of biochar-supported materials with a focus on their applications for different contaminants’ removal and the underlying mechanisms are also discussed.
Chapter 8 focuses on biological processes for swine wastewater treatment. Therefore, it details the swine wastewater characteristics, microorganisms, metabolic pathways involved, and biological processes in swine wastewater treatment. Besides, challenges and prospects in this research field are also presented.
Chapter 9 discusses various imperative techniques to detect hazardous metal ions in various water reservoirs. The toxicological effects of various metal ions on living beings and atmosphere along with their detection limits, in addition to future perspectives of these procedures, are highlighted.
Chapter 10 discusses the production of hydrogen-rich water and its role in medical applications. Firstly, a concise discussion of two of the production methods of hydrogen-rich water is provided. Lastly, the medical benefits, medical applications, and the safety of hydrogen-rich water are discussed in detail.
Chapter 11 focuses on the application of hydrosulfide treatment in medicine, agriculture, and industry fields. Hydrosulfide anion is considered as an innovative gaseous signaling molecule and plays significant biological roles in the organisms. Its performance is discussed in detail for the improvement of biotic/abiotic stress tolerance of cells.
Chapter 12 discusses the properties of available radionuclides including uranium, lead, polonium, cesium, strontium, thorium, radon, and radium. Moreover, the health problem caused due to these radionuclides contaminated water is also highlighted. Techniques involved in the removal of radionuclides including ion exchange, aeration, filtration, nanofiltration, and flocculation are summarized.
Chapter 13 reviews the developing applications of membrane contactors in water treatment and desalination demonstrating their ability to substitute or supplement the conventional separation processes. The advantages and limitations of membrane contactors are discussed and their potential for value recovery from spent streams of small and medium industries are highlighted.
Chapter 14 comprehensively reviews all the sulfate remediation technologies and also lists various methods involved in tackling the sulfate problem from wastewater. Both conventional methods and modern-day technologies are covered in this chapter for sulfate removal.
Chapter 15 discusses the various sources and pathways of heavy metals’ movement and accumulation in the environment. The toxicity effects of these heavy metals on human health are also presented. Various bio-indicators and biomarkers generally used for the assessment of heavy metal-based pollution about intake, hazard, toxicity, and transfer factor are discussed. Also, details of various indices associated with health risk, carcinogenic risk, and exposure assessment are focused and recommended.
Chapter 16 emphasizes that the analysis of water is an important multistep process and vital for surveillance and management. The monitoring should be a dynamic procedure with the adoption of techno-economic and state-of-art techniques. We need to improve water quality, minimize pollutants, conserve for the generations, and upgrade awareness levels. Every drop of water counts and has the hidden story of life.
Chapter 17 deals with chemical standards for water quality and explains the philosophy of establishing these standards. In addition to the effect of inorganic substances on water quality, it takes into account the future development of water analysis to make water clean and suitable for human use.
Chapter 18 describes the different approaches used to measure water both quantitatively and qualitatively. The dischargeable and acceptable limits are also tabulated in this chapter as per WHO and BIS guidelines. The simulation equations for estimating the water quality index are presented. Additionally, wastewater treatment techniques are also explained in three stages.
Chapter 19 discusses the application of nanofluids as one of the sustainable bioremediation techniques for the treatment and purification of heavily contaminated water. Different types of nanofluids used in the treatment of water such as zero-valent metal nanoparticles, metal oxides nanoparticles, carbon nanotubes, and nanocomposites are also highlighted.
1Sorbent-Based Microextraction Techniques for the Analysis of Phthalic Acid Esters in Water Samples
Miguel Ángel González-Curbelo1, Javier González-Sálamo2,3, Diana A. Varela-Martínez1,2 and Javier Hernández-Borges2,3*
1Departamento de Ciencias Básicas, Facultad de Ingeniería, Universidad EAN, Bogotá D.C., Colombia
2Departamento de Química, Unidad Departamental de Química Analítica, Facultad de Ciencias, Universidad de La Laguna (ULL). Avda. Astrofísico Fco. Sánchez, San Cristóbal de La Laguna, España
3Instituto Universitario de Enfermedades Tropicales y Salud Pública de Canarias, Universidad de La Laguna (ULL). Avda. Astrofísico Fco. Sánchez, San Cristóbal de La Laguna, España
Abstract
Current society is living in a world in which it is exposed to a broad spectrum of contaminants that can pose different risks for health. In this sense, we are daily bombarded with news related to pollution by plastic residues (especially in the oceans), being one of the main issues that humans must face today, not only because of the direct effects of plastics but also because of the variety of contaminants they can release to the environment. Probably, the most important ones are phthalic acid esters (PAEs), since they easily migrate from the polymeric matrix to the surrounding media, acting as endocrine disruptors in human organisms and resulting in multiple diseases. Their occurrence in water matrices is of especial importance, since it is essential for life, and the presence of PAEs, even at very low levels, can cause serious health problems. This book chapter aims at providing a general and critical overview of the different analytical methodologies that have been developed for the analysis of PAEs in water samples and which are based on the application of sorbent-based microextraction techniques, which is one of the current trends in the Analytical Chemistry field.
Keywords: Phthalic acid esters, analytical methods, sample preparation, microextraction techniques, water samples, sorbents
1.1 Introduction
Phthalic acid esters (PAEs) are a group of dialkyl or alkylaryl esters of phthalic acid (see Figure 1.1), commonly known as phthalates, which are widely used as additives in the polymer industry but also added to paints, adhesives, lubricants, and cosmetics, among others [2]. As an example, low-molecular PAEs such as butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), and diethyl phthalate (DEP) are widely used as solvents and emulsifiers to maintain color and fragrance mainly in beauty products and pharmaceuticals, while high-molecular PAEs such as di(2-ethylhexyl) phthalate (DEHP) are highly used as plasticizers to make polymeric materials more workable and flexible. As a result of the extremely high production of such products, especially plastics, PAEs are exorbitantly present in the daily life. Among them, DEHP is the most currently used. In fact, its production as plasticizer is estimated to be a quarter of the total [3, 4]. Due to these widespread applications and intensive production, together with the fact that they are only retained in the polymer structure through weak secondary molecular interactions and not covalently, PAEs can easily migrate to the environment. As a result, PAEs have become ubiquitous contaminants in the environment, in particular, they can be found in natural waters such as lake, river, sea, and ground waters [5, 6], especially those adjacent or downstream from industrial locations [5]. In addition, their possible migration to drinking waters that are in contact with plastic materials like mineral and tap waters must also be taken into account, as well as their final presence in waste waters [5, 7].
It has already been demonstrated that many PAEs act as endocrine disruptors and that they can be toxic for reproduction, even at extremely low concentrations [8–11]. Even more worrying is the fact that certain PAEs can be easily degraded in the environment by bacteria and fungi and their degradation products can also have an important toxicity. Such is the case of DEHP that can be degraded to DBP, DEP, and especially to mono-2-ethylhexyl phthalate (MEHP), which has shown to be more toxic than DEHP [12, 13] (see Figure 1.2). As a result of the high human exposure to PAEs and their metabolites, their potential risks for health and their persistence, several organizations have established an increasingly broad and restrictive legislation. As examples, the European Union has listed several PAEs as compounds suspected to produce endocrine abnormalities [15] and the International Agency for Research on Cancer has classified DEHP in the group 2B (possibly carcinogenic to humans) [16]. Moreover, the US Environmental Protection Agency (EPA) has included several PAEs (BBP, DBP, DEHP, DEP, dimethyl phthalate (DMP), and di-n-octyl phthalate (DNOP)) in its priority list of pollutants and has established limits of 6 μg/L and 400 μg/L for DEHP and di(2-ethylhexyl) adipate (DEHA) in drinking water, respectively [17], while this maximum allowed concentration has been established in 8 μg/L for DEHP by the World Health Organization [18] and in 1.3 μg/L in surface waters by the European Union [19]. Considering all the above mentioned, it is clear that there is an increasing need to develop highly sensitive and reliable analytical methods for monitoring trace amounts of PAEs in different samples and, especially, in water.
Figure 1.1 The chemical structures of PAEs. Adapted from [1]. PAEs, phthalic acid esters.
Figure 1.2 DEHP biodegradation pathways to obtain MEHP, DBP, and DEP. Reprinted from [14] with permission from Elsevier. DBP, dibutyl phthalate; DEHP, di-2-ethylhexyl phthalate; DEP, diethyl phthalate; MEHP, mono-2-ethylhexyl phthalate; PA, polyacrylate.
PAEs have been analyzed in water samples using gas chromatography (GC) coupled to flame ionization detectors (FIDs) [20], mass spectrometry (MS) [21] and tandem MS (MS/MS) [22], or highperformance liquid chromatography (HPLC) coupled to diode array detectors (DADs) [23], ultraviolet (UV) [24], and MS [25]. Among them, GC is normally the preferred technique since most PAEs are nonpolar and thermostable. It is important to notice that, in all these analytical methods, it has been necessary to include previous sample preparation steps before instrumental analysis to achieve accurate and sensitive results. These steps consist on the isolation and pre-concentration of PAEs since they can be found in water samples at extremely low concentrations. However, since PAEs are not ionizable in water, these samples are normally analyzed directly or after a simple filtration without pH adjustment regardless of the sample preparation technique used in each case [26].
In this context, special attention should be paid to the risk of sample contamination during their analysis, which would result in false positives and/or over-estimated concentrations. As it has already been said, PAEs are ubiquitous contaminants and this includes their possible presence in any laboratory since they can be found in solvents, reagents, filters, etc. Consequently, previous washing steps using PAE-free solvents, if possible (since most organic solvents also contain some PAEs), subsequent heating of non-volumetric glassware at high temperatures (450–550°C) for several hours (4–5 h), washing volumetric or any glassware material with strong oxidizing agents, and, in some cases, even wrapping in heat-treated aluminum foil to avoid adsorption of PAEs from the air are carried out, among others [27–29]. Despite all these precautions, residues of PAEs may finally appear, and the analysis of blanks should be developed on a daily basis in every batch of samples so that background levels can be suitably subtracted [21, 25, 30].
Until very recently, the most widely used sample preparation methods, also for the analysis of PAEs in water samples, have been based on the use of liquid-liquid extraction (LLE) and solid-phase extraction (SPE) [31, 32]. The need for developing quicker, simpler, and miniaturized extraction procedures able to maintain or even to improve the required sensitivity of the analysis has resulted in the development of new sample preparation techniques. In this sense, microextraction techniques have gained notoriety since the extraction is carried out using amounts of extracting phase much smaller than the sample amount (extraction of analytes is not always exhaustive). Microextraction techniques have inherent advantages such as exceptionally high enrichment factors, simplicity, time saving, and the generation of small amounts of organic solvent or reagents wastes, without affecting reproducibility, and compatibility with most analytical instrumentation [33–36]. Among these new alternatives, sorbent-based microextraction techniques have been widely used due to the great diversity of commercially available sorbents, as well as new extraction sorbents (in particular nanomaterials) that are constantly being proposed for their direct use or after a previous functionalization to enhance their selectivity [35–37].
As a result of the above-mentioned issues, the aim of this book chapter is to provide a general overview of the sorbent-based microextraction techniques applied to the analysis of PAEs in water samples, which mainly include solid-phase microextraction (SPME), dispersive SPE (dSPE), and magnetic dSPE (m-dSPE), among others. The extraction ability to quantitatively and selectively extract these target analytes will be commented and discussed.
1.2 Solid-Phase Microextraction
SPME has been the sorbent-based microextraction technique most used for the analysis of PAEs in water samples (see Table 1.1) probably, among other reasons, because it allows to reduce the risk of PAEs contamination during sample extraction with respect to other conventional extraction techniques. On the one hand, the absence of organic solvents and additional steps reduces PAEs background levels. On the other, water is in many occasions a simple and clean matrix that contains few interferences, so the direct immersion (DI) mode can be used without hardly any impairment of its lifetime (except for waste waters or marine water). Moreover, in SPME, extraction, pre-concentration and direct desorption into analytical instruments can be easily integrated in most cases.
The first studies in which SPME was applied for PAEs extraction from water samples dealt with the direct application of commercial fiber coatings, including polydimethylsiloxane (PDMS), polyacrylate (PA), PDMS-divinylbenzene (DVB), carboxen (CAR)-PDMS, and carbowax (CW)-DVB. As examples, Cao [21] demonstrated the better performance of PDMS-DVB fibers compared to PDMS and DVB-CAR-PDMS fibers for the headspace (HS) SPME extraction of nine PAEs (DMP, DEP, DIBP, DBP, BBP, DHXP, DEHA, DEHP, and DNOP) from bottled water samples, while Polo et al. [28] found that PDMS-DVB fibers also give higher extraction efficiency than PDMS, PA, CAR-PDMS, and CW-DVB fibers for DBP, BBP, and DNOP, but CAR-PDMS and PA fibers show a better extraction performance for DMP and DEP, and for DEHP, although the first one provided better results for simultaneous analysis of the target PAEs from bottled, industrial harbor, river, urban collector, and influent and effluent waste water samples. As expected, the optimal SPME fiber for the extraction of a particular phthalate depends on both the properties of the coating and the PAEs since these compounds differ from each other in terms of polarity and volatility and, therefore, on their distribution between the fiber coating and the matrix. In addition, low-molecular PAEs are more volatile than those of high-molecular weight [38]. As a result, low-molecular PAEs would be expected to be more efficiently extracted when HS mode is used [38]. However, they have a certain solubility in water and, as consequence, they volatilize very slowly from this kind of matrices. Contrary, although high-molecular PAEs are less volatile, they have a lower water solubility and they volatilize faster at higher temperatures than it could be expected [38]. Accordingly, it has been observed that DEHP and DNOP are extracted from different water samples more efficiently than BBP, DEP, and DMP using HS-SPME [28, 39]. Nevertheless, most of the works published on this topic are based on DI-SPME instead of HS-SPME.
Table 1.1 Some examples of the application of SPME and SBSE for the analysis of PAEs in water samples.
PAEs
Matrix (sample amount)
Sample pretreatment
Separation technique
LOQ
Recovery study
Residues found
Comments
Reference
SPME
DMP, DEP, DBP, BBP, DEHP, and DNOP
Mineral, river, industrial port, sewage, and waste waters (10 mL)
SPME using a PDMS-DVB fiber, stirring at 100°C in DI mode for 20 min, and desorption at 270°C for 5 min
GC-MS
0.0067–0.34 μg/L
87–110% at 0.5 and 2.5 μg/L
One sample of each water were analyzed and contained all PAEs at levels from 0.011 to 6.17 μg/L
A multifactor categorical design was used for optimization purposes. PDMS-DVB fiber showed higher extraction efficiency than PDMS, PA, CAR-PDMS and CW-DVB fibers for DBP, BBP, and DNOP, but CAR-PDMS for DMP and DEP, and PA for DEHP. DI-SPME provided better sensitivity than HS mode
[28]
DEHA, DMP, DEP, BBP, DIBP, DBP, DHXP, DEHP, and DNOP
Mineral water (10 mL plus 10 or 30% w/v NaCl)
SPME using a PDMS-DVB fiber, stirring at 90°C in DI mode for 60 min, and desorption at 270–280°C for 5 min
GC-MS
-
-
Eleven samples were analyzed and residues of DEP, DIBP, DBP, and DEHP were found at levels from 0.052 to 1.72 μg/L
PDMS-DVB fiber showed higher extraction efficiency than PDMS and DVB-CAR-PDMS fibers
[21]
DPP, DBP, DIBP, and DNPP
Mineral and tap water (10 mL)
SPME using a MWCNTs-PPy fiber, stirring at room temperature in DI mode for 60 min, and desorption at 250°C for 25 min
GC-FID
0.17–0.33 μg/L
90–113% at 5 and 50 μg/L
Three mineral water samples and 1 tap water were analyzed and contained at least 1 PAE at levels from 0.6 to 7.90 μg/L, except 1 of the mineral water samples
-
[40]
DMP, DEP, DBP, DAP, and DNOP
Mineral, tap and reservoir waters (12 mL plus 10% w/v NaCl)
SPME using a MIP fiber, stirring at 60°C in DI mode for 30 min, and desorption at 250°C for 10 min
GC-MS
0.0072–0.069 μg/L
94.54–105.34%
One sample of each water were analyzed and contained at least 2 PAEs at levels from 0.07 to 0.53 μg/L
DBP was used as the template molecule. MIP fiber showed higher extraction efficiency than a non-imprinted polymer fiber, and PDMS, PA and CW-DVB fibers
[45]
DMP, DEP, DBP, BBP, DEHP, DINP, and DNOP
Water (5 mL plus 6% w/v NaCl)
SPME using a PA fiber, stirring at room temperature in DI mode for 50 min, and desorption at 270°C for 2 min
GC-MS
0.007–0.027 μg/L
-
Six samples were analyzed and contained at least 2 PAEs at levels from 0.4 to 78.8 μg/L
PA fiber showed higher extraction efficiency than PDMS fiber. Urine was also analyzed
[95]
DIBP, DBP, BMPP, DNPP, DHXP, BBP, DCHP, DEHP, DIPP, DNOP, and DINP
River and tap waters (- mL)
SPME using a bamboo charcoal fiber, stirring at room temperature in DI mode for 20 min, and desorption at 280°C for 10 min
GC-MS
0.013–0.067 μg/L
61.9–87.1% at 0.1, 0.5, and 1 μg/L
One sample of each water were analyzed and no residues were detected
Bamboo charcoal fiber showed greater extraction efficiency than PDMS, PDMS-DVB and PA fibers for DNOP and DINP, but lower for DIBP, DBP, and DNPP
[47]
DBP, DIBP, BBP, and DEHP
Mineral water (9 mL plus 20% w/v NaCl)
SPME using a TiO
2
NPs fiber, stirring at 30°C in DI mode for 75 min, and desorption at 285°C for 5 min
GC-FID, GC-MS
0.17–0.40 μg/L
86–107% at 2μg/L
One sample was analyzed and residues of DIBP and DEHP were found at 1.0 and 2.2 μg/L, respectively
TiO
2
NPs fiber showed better extraction efficiency than PDMS and poly(3,4-ethylenedioxythiophene)-TiO
2
fibers. DI-SPME provided better sensitivity than HS mode
[39]
DMP, DEP, DBP, and DEHP
Mineral, river and tap waters (15 mL)
SPME using a SiO
2
-PDMS-MWCNTs fiber, stirring at 40°C in DI mode for 30 min, and desorption at 280°C for 2 min
GC-FID
0.033–0.067 μg/L
79.62–109.3% at 10 μg/L
One sample of each water were analyzed and residues of DBP and DEHP were found at 5.26 and 8.47 μg/L, respectively, in the mineral water sample
SiO
2
-PDMS-MWCNTs fiber showed better extraction efficiency than PDMS, PA and DVB-CAR-PDMS fibers
[43]
DPP, DIBP, DBP, DNPP, BBP, and DEHP
Mineral and tap waters (10 mL)
SPME using a poly-
o
-aminophenol-MWCNTs fiber, stirring at 35°C in DI mode for 60 min, and desorption at 280°C for 2 min
GC-FID
0.10–0.25 μg/L
91–115% at 5 and 50 μg/L
Three mineral water samples and 1 tap water sample were analyzed and contained at least 2 PAEs at levels from 0.3 ± 0.02 to 8.1 ± 0.19 μg/L, except for 1 mineral water sample
NaCl and dextrose injection solutions were also analyzed
[42]
DBP, BBP, DEHA, DEHP, and DNOP
Tap, barreled drinking and pond waters (10 mL plus 15% w/v NaCl)
SPME using a PS-MWCNTs fiber, stirring at room temperature in DI mode for 60 min, and desorption at 280°C for 5 min
GC-MS/MS
0.0038-0.059 μg/L
73.4-103.8% at 0.05 and 0.2 μg/L
One sample of each water were analyzed and contained at least 1 PAE at levels from 0.038 ± 0.004 to 0.060 ± 0.007 μg/L
A Box-Behnken design was used for optimization purposes
[41]
DPP, DBP, DEHA, and DEHP
Mineral, tanked and tap waters, and boiling water exposed to a PET container (10 mL plus 30% w/v NaCl)
SPME using a G-PVC fiber, stirring at 70°C in HS mode for 35 min, and desorption at 230°C for 4 min
GC-FID
0.2–0.3 μg/L
88–108% at 10 and 20 μg/L
One sample of each water were analyzed and residues of DPP and DBP were found at 2.1 and 1.8 μg/L, respectively, only in the boiling water exposed to a PET container
A central composite design was used for optimization purposes. Sunflower and olive oils were also analyzed
[20]
DMP, DEP, DIBP, DBP, DMEP, BMPP, DEEP, DNPP, BBP, DHXP, DBEP, DCHP, DPhP, DEHP, DNOP, and DINP
Sea water (10 mL)
SPME using a PDMS fiber, stirring at 35°C in DI mode for 40 min, and desorption at 40°C for 6 min
GC-MS
0.00017–0.0011 μg/L
68.0–114.0%, but 55.4% for DMP, at 100 and 300 μg/L
Eleven sample was analyzed and contained at least 9 PAEs at levels from 0.270 to 1.39 μg/L
Sediment was also analyzed by conventional SPE
[96]
DEP, DIBP, DBP, BBP, and DEHP
River, bottled and mineral waters (4 mL plus 20% w/v NaCl)
SPME using a polyamide6-MnO fiber, stirring at 80°C in HS mode for 30 min, and desorption at 200°C for 5 min
GC-μ-ECD
0.13–0.64 μg/L
90.3–106% at 10 and 100 μg/L
One sample of each water were analyzed and residues of DEP, DIBP and DBP were found at levels from 9.24 to 29.3 μg/L, respectively, in the bottle and mineral waters
Polyamide6-MnO fiber showed better extraction efficiency than PDMS fiber. Soda was also analyzed
[44]
DMP, DEHP, DBP, DNPP, BBP, and DNOP
Tap and sea water (20 mL adjusted at pH 4)
SPME using a GO-1-(3-aminopropyl)-3-vinyl imidazolium bromide/tetrafluoroborate fiber, stirring at 35°C in DI mode for 30 min, and desorption at 175°C for 5 min
GC-MS
0.017–0.10 μg/L
87.6–101.2% at 1 and 5 μg/L
One sample of each water were analyzed, and no residues were detected
GO-1-(3-aminopropyl)-3-vinyl imidazolium bromide fiber showed higher extraction efficiency than GO-1-(3-aminopropyl)-3-vinyl imidazolium tetrafluoroborate, PA and CAR-PDMS fibers. Coffee was also analyzed
[52]
DEP, DPP, DAP, DBP, BBP, and DEHP
Water (- mL plus 20% w/v NaCl)
SPME using a OH-TPB-COFs fiber, stirring at 105°C in HS mode for 50 min, and desorption at 250°C for 7 min
GC-FID
0.11–1.50 μg/L
78.6–101.9% at 1 and 5 μg/L
Three sample were analyzed and contained at least 4 PAEs at levels from 1.39 to 5.78 μg/L
OH-TPB-COFs fiber showed better extraction efficiency than PDMS fiber
[46]
DMP, DBP, DINP, DEP, BBP, DEHP, DNOP, and DIDP
Mineral water (9 mL)
IT-SPME using AC-PS-DVB monolithic columns, and desorption with 1.5 mL ACN
CE-DAD, UHPLC-UV
0.59–9.83 μg/L
78.8–104.6% at 50 μg/L
One sample was analyzed, and no residues were detected
AC-PS-DVB monolithic column showed better extraction efficiency than AC-poly(BMA-EDMA) monolithic column. ACN showed higher extraction efficiency than MeOH as desorption solvent.
[62]
DMP, DEP, DAP, BBP, DBP, DNPP, and DCHP
Disposable tableware, plastic cup and river waters (45 mL plus 2% v/v MeOH)
IT-SPME using PDA-melamineformaldehyde aerogel-carbonfiber tube, and desorption with MeOH-water for 0.6 mL
HPLC-DAD
0.07–0.16 μg/L
77–120% at 10 and 15 μg/L
One sample of each water were analyzed and residues of DAP, BBP and DNPP were found at levels from 0.12 to 0.99 μg/L in the water in plastic cup
PDA-melamineformaldehyde aerogelcarbon-fiber tube showed better extraction efficiency than melamine-formaldehyde aerogel-carbon-fiber and bare carbon-fiber tubes
[23]
SBSE
DMP, DEP, DBP, BBP, DEHP, and DNOP
Sea and esturiane waters (20 mL plus 30% w/v NaCl and 20% v/v MeOH)
SBSE using a PDMS stir bar, stirring at room temperature for 60–200 min, and thermal desorption at 300°C for 10 min
GC-MS
0.0003–0.063 μg/L
95–124% at 0.1 μg/L
One river water sample and 2 estuarian water samples were analyzed and contained all PAEs at levels from 0.0036 ± 0.0004 to 1.314 ± 0.018 μg/L
A Plackett–Burman and 2 central composite designs were used for optimization purposes. 6 polycyclic aromatic hydrocarbons, 12 polychlorinated biphenyls and 3 nonylphenols were also analyzed
[65]
DMP, DEP, DIBP, DBP, DMEP, DMPP, DEEP, DNPP, DHXP, BBP DBEP, DCHP, DEHP, DPhP, and DNOP
Sea water (25 mL plus 5% w/v NaCl and 10% v/v MeOH)
SBSE using a PDMS stir bar, stirring at room temperature for 120 min, and desorption with 200 μL MeOH and 50 μL ACN by sonication for 50 min
GC-MS
0.00027–1.63 μg/L
-
No samples were analyzed
The stir bar coated with 150 μl PDMS showed higher extraction efficiency than coated with 50 μL and 75 μL PDMS, and 150
μL
PDMS over carbon film. A mix MeOH-ACN showed higher extraction efficiency than MeOH and dichloromethane as desorption solvent
[66]
μ-ECD, micro-electron capture detector; AC, activated carbon; ACN, acetonitrile; BBP, benzylbutyl phthalate; BMA, butyl methacrylate; BMPP, bis(4-methyl-2-pentyl) phthalate; CAR, carboxen; CE, capillary electrophoresis; COFs, covalent organic frameworks; CW, carbowax; DAD, diode-array detector; DAP, diallyl phthalate; DBEP, di(2-butoxyethyl) phthalate; DBP, dibutyl phthalate; DCHP, dicyclohexyl phthalate; DEEP, di(2-ethoxyethyl) phthalate; DEHA, di(2-ethylhexyl) adipate; DEHP, di(2-ethylhexyl) phthalate; DEP, diethyl phthalate; DHXP, dihexyl phthalate; DI, direct immersion; DIBP, diisobutyl phthalate; DIDP, diisodecyl phthalate; DINP, diisononyl phthalate; DIPP, diisopentyl phthalate; DMEP, di(2-methoxyethyl) phthalate; DMP, dimethyl phthalate; DMPP, dimethylethyl phthalate; DNOP, di-n-octyl phthalate; DNPP, di-n-pentyl phthalate; DPhP, diphenyl phthalate; DPP, dipropyl phthalate; DVB, divinylbenzene; EDMA, ethylene dimethacrylate; FID, flame ionization detector; G, graphene; GC, gas chromatography; GO, graphene oxide; HPLC, high-performance liquid chromatography; HS, headspace; IT-SPME, in tube-solid-phase microextraction; LOQ, limit of quantification; MeOH, methanol; MIP, molecularly imprinted polymer; MS/MS, tandem mass spectrometry; MS, mass spectrometry; MWCNTs, multi-walled carbon nanotubes; NPs, nanoparticles; PA, polyacrylate; PAE, phthalic acid ester; PDA, poly(dopamine); PDMS, polydimethylsiloxane; PET, polyethylene terephthalate; PPy, polypyrrole; PS, polystyrene; PVC, polyvinylchloride; SBSE, stir bar sorptive extraction; SPE, solidphase extraction; SPME, solid-phase microextraction; TPB, 2,4,6-triphenoxy-1,3,5-benzene; UHPLC, ultra-performance liquid chromatography; UV, ultraviolet.
As it has already been said, the fiber coating plays a key role in the SPME of PAEs from water samples. However, the types of commercial fibers are still limited, which reduces their application field. In addition, under certain conditions they have low thermal and chemical stability. Furthermore, they are fragile since they are based on fused silica supports. Consequently, most of the subsequent studies have been focused on developing new highly selective, efficient, inexpensive, and robust SPME fibers with controllable thickness through different coating techniques. For this purpose, a wide variety of new fibers based on the use of carbon-based nanomaterials [40–43], metal oxide nanoparticles (NPs) [39, 44], molecular imprinted polymers (MIPs) [45], covalent organic frameworks (COFs) [46], and bamboo charcoal [47] have been reported, among others.
The development of carbon-based coatings for stainless-steel fibers has been an important research field as a result of the exceptional properties these materials have, such as great chemical and thermal stability, high surface area and great capacity to establish π-π interactions with the aromatic groups of the PAEs [37, 48, 49]. Moreover, they can be easily dispersed in a polymer matrix to obtain coatings that provide considerably better characteristics than those of virgin polymers. Among them, multi-walled carbon nanotubes (MWCNTs) have been the most used, which are large molecules composed by numerous electronically aromatic delocalized carbon atom layers and rolled up into a cylinder. As examples of the use of this kind of coatings for the extraction of PAEs from water samples, Asadollahzadeh et al. [40] made a fiber coated with an oxidized MWCNTs-polypyrrole (PPy) composite while Behzadi et al. [42] used MWCNTs-poly-o-aminophenol, both obtained through electrochemical polymerization, for the extraction of mineral water samples. Song et al. [41] also prepared a MWCNTs-polystyrene (PS) material via electrostatic interactions as SPME coating, and Zhang et al. [43] developed a SiO2-PDMS-MWCNTs fiber by a sol-gel method. In both cases, drinking and environmental water samples were analyzed. All these fiber coatings presented a porous structure with very large surface areas where both phases (the MWCNTs and polymer) took part in the extraction procedure, enhancing the final adsorption capacity of the fiber. Moreover, in the last work, the organic-inorganic bilayer structure was designed to increase the stability and durability of the coating. In particular, a stainless-steel fiber was coated with a SiO2 layer, which was used as support for the chemical bonding of the second layer of PDMS-MWCNTs (see Figure 1.3). The first coating with a SiO2 layer is a general procedure widely used for coating different surfaces or particles [50, 51]. Compared with commercial PDMS, PA, and DVB-CAR-PDMS fibers, this new coating showed better extraction efficiency and longer lifetimes (150 vs. 50–100 times) for the extraction of DMP, DEP, DBP, and DEHP. It is also noteworthy to mention the extensive study that was conducted by these authors to evaluate the influence of salt addition on the extraction efficiency. It was observed that the addition of different kinds of salts such as NaCl, CaCO3, FeCl3, and MgCl2 at different concentrations (0%, 5%, 10%, and 15%, w/v) can have a negative or a negligible effect on the recovery values. Therefore, no salt was added to the samples, as in the vast majority of the published works on this topic (see Table 1.1).
Figure 1.3 Schematic representation of the SiO2-PDMS-MWNTs fiber preparation. Reprinted from [43] with permission from The Royal Society of Chemistry. MWNTs, multi-walled carbon nanotubes; TEOS, tetraethoxysilane; TSO-OH, hydroxyl terminated silicone oil.
Graphene is another of the allotropic forms of carbon that has been used as SPME coating. It consists of a monolayer of sp2 hybridized carbon atoms arranged in a 2D network. Like MWCNTs, graphene has a high surface area, high chemical and thermal stability as well as a high affinity for hydrophobic and aromatic compounds. Then, graphene-polymer nanocomposites have also been used as excellent SPME fiber coatings for the extraction of PAEs. Such is the case of the work developed by Amanzadeh et al. [20] in which a stainless-steel fiber was coated using a new graphene/polyvinylchloride (PVC) material and evaluated successfully as a SPME fiber for the extraction of dipropyl phthalate (DPP), DBP, DEHA, and DEHP from drinking waters and sunflower and olive oil samples. However, even though it was used in the HS mode, a single fiber could be used only 60 times without a significant decrease in the extraction efficiency. As a very interesting experiment, these authors also determined these PAEs in boiling water exposed to a polyethylene terephthalate (PET) bottle. Although the water used did not contain residues of any of the target PAEs at the beginning, residues of DPP and DBP were found at 2.1 and 1.8 μg/L, respectively, after filling this bottle with the same water just after boiling (it was analyzed after cooling). That is, the PAEs with low molecular weight (250.2 g/mol for DPP and 278.3 g/mol for DBP compared to 370.5 g/mol for DEHA and to 390.5 g/mol for DEHP) have larger water solubility, so these kinds of PAEs migrated more easily from PET bottles containing hot water.
Another example of the benefits of using graphene, is the work of Tashakkori et al. [52] who prepared SPME fibers based on the use of the ionic liquid (IL) 1-(3-aminopropyl)-3-vinyl imidazolium bromide and 1-(3-aminopropyl)-3-vinyl imidazolium tetrafluoroborate grafted onto graphene oxide (GO) previously deposited onto stainless-steel wires. On the one hand, GO disperses more easily for the first preparation step and inherits the mechanical properties of graphene but with a moderate decrease of mechanical parameters (Young’s modulus and intrinsic strength) due to the alterations produced in the sp2 structure [53, 54]. On the other hand, ILs can be structurally customized based on diverse procedures to tune the extraction performance [55]. In fact, ILs can establish a broader variety of interactions with the analytes such as π-π, dipolar, hydrogen bonding, and ionic/charge-charge [56]. As a result, they are also suitable for the extraction of hydrophobic compounds and aromatic analytes like PAEs. Consistently, the first GO-IL fibers showed better extraction efficiency for the analysis of DMP, DEHP, DBP, DNPP, BBP, and DNOP in tap and sea water samples (also in instant coffee samples) than other lab-made fiber, as well as commercial PA and CAR-PDMS fibers, using DI mode in all cases.
MIPs also provide a great improvement in selectivity since they have cavities specifically designed for a particular compound or group of analogous compounds [57, 58]. That is to say, retention occurs through a molecular recognition mechanism based on their size, shape and three-dimensional distribution of functional groups [59]. He et al. [45] demonstrated that MIPs are quite suitable as SPME fiber coatings for the successful extraction of low (DMP, DEP, DBP, and diallyl phthalate -DAP-) and high-molecular PAEs (DNOP) simultaneously, from bottled, tap, and reservoir water samples, although it is true that the latter was poorly extracted since DBP was used as template molecule during the synthesis of the polymer. Moreover, the peak areas obtained using the MIP fiber were much higher than those using a non-imprinted fiber prepared with the same protocol (without the addition of the template molecule), but also better compared to commercial PDMS, PA, and CW-DVB fibers (see Figure 1.4). These results indicate that the MIP fiber provided a better selectivity for the structural analogues of DBP, while commercial SPME coatings are more susceptible to undesirable interferences in the extraction process.
