Challenges in Green Analytical Chemistryby Sergio A Estrela
Concerns about environmental pollution, global climate change and hazards to human health have increased dramatically. This has lead to a call for change in chemical processes including those that are part of chemical analysis. The development of analytical chemistry continues and every new discovery in chemistry, physics, molecular biology, and materials science
Concerns about environmental pollution, global climate change and hazards to human health have increased dramatically. This has lead to a call for change in chemical processes including those that are part of chemical analysis. The development of analytical chemistry continues and every new discovery in chemistry, physics, molecular biology, and materials science brings new opportunities and challenges. Yet, contemporary analytical chemistry does not consume resources optimally. Indeed, the usage of toxic chemical compounds is at the highest rate ever. All this makes the emerging field of green chemistry a "hot topic" in industrial, governmental laboratories as well as in academia. This book starts by introducing the twelve principles of green chemistry. It then goes on to discuss how the principles of green chemistry can be used to assess the 'greenness' of analytical methodologies. The 'green profile' proposed by the ACS Green Chemistry Institute is also presented. A chapter on "Greening" sample preparation describes approaches to minimizing toxic solvent use, using non-toxic alternatives, and saving energy. The chapter on instrumental methods describes existing analytical approaches that are inherently green and making non-green methods greener. The final chapter on signal acquisition describes how quantitative structure-property relationship (QSPR) ideas could reduce experimental work thus making analysis greener. The book concludes with a discussion of how green chemistry is both possible and necessary. Green Analytical Chemistry is aimed at managers of analytical laboratories but will also interest teachers of analytical chemistry and green public policy makers.
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Challenges in Green Analytical Chemistry
By Miguel de la Guardia, Salvador Garrigues
The Royal Society of ChemistryCopyright © 2011 Royal Society of Chemistry
All rights reserved.
An Ethical Commitment and an Economic Opportunity
M. DE LA GUARDIA AND S. GARRIGUES
Departamento de Química Analítica, Edificio de Investigación, Universidad de Valencia, C/. Dr. Moliner 50, 46100 Burjassot, Valencia, Spain
The side effects of the use of analytical methodologies may involve serious risks for operators as well as damage to the environment, and for these reasons it is relevant to think about the consequences of our activity as researchers or users of analytical methods.
Both from the point of view of citizens interacting ethically with the environment and as part of a fundamental evaluation of the costs of analytical procedures, we must take into consideration the inherent risks of some types of samples, together with the extensive use of chemical reagents and solvents, the energy consumption associated with modern instrumentation and, of course, the laboratory wastes and emissions resulting from the various steps of analytical procedures. This last aspect involves consumables and also the budget required to avoid or repair environmental damage.
Our view of analytical chemistry therefore involves moral and economic factors. We consider that the greening of analytical methodologies offers excellent business opportunities, as well as being a result of our moral commitment to our society and our future.
1.1 Green Analytical Chemistry in the Framework of the Ecological Paradigm of Chemistry
The foundation of chemistry as a scientific discipline can be dated to the publication of the Traité élémentaire de chimie by A. L. de Lavoisier in 1789. His work involved organizing chemical knowledge with respect to the experimental evidence, and created the basis of a paradigm focused on the atomic and molecular structure of matter and the relationship between the composition of matter and its behaviour.
As Professor Malissa has clearly explained, the old chemical practices coming under the general heading of 'archeochemistry' were the first para digm of chemistry providing the basis for the development of metal and alloy technologies, gold analysis, and developments in ceramics. This step was followed by the philosophical and experimental development of alchemy, a type of magic, which was introduced into the early universities through a study of the chemistry of natural products as pharmaceutical tools, thus creating the period of 'iatrochemistry'. In this framework the 'chemiological' era began with scientific evidence of the nature of the chemical composition of matter and the relationship between structure and properties of materials, and, based on the rapid development of synthesis, provided the tools for a 'chemiurgical' period.
For the general public and for our students, most ideas about chemistry are probably based on the capacity of chemical principles and practices to create new materials and to transform our lives. However, it is also clear that as well as its beneficial effects the chemical revolution has caused terrible damage. Today we cannot imagine our life without many of the developments of the chemiurgical period, such as the introduction of petroleum-based fuels, the synthesis of pharmaceuticals and phytosanitary products, and many other industrial products, in spite of the environmental consequences and the risks to our lives caused by the use of chemical compounds.
The bad conscience of chemists and consumers about the side effects of chemicals has created a new view of chemical problems, which Malissa calls the 'ecological paradigm'; this aims to put chemical knowledge within the frame of environmental equilibrium. In the new framework of a sustainable chemistry all problems, from synthesis to individual applications, including analytical methods, must be evaluated in order to avoid collateral damage. This is especially important for the analytical community who, day after day, use large quantities of reagents and solvents to check the chemical composition of samples in every imaginable field, from natural sources to industrial processes and products, from the analysis of soils to that of water and air, not to mention the study of biota and the clinical evaluation of human health.
As Professor George Pimentel said in his Opportunities in Chemistry report to the U.S. National Academy of Sciences, there is a need to increase the proportion of research and development devoted to exploratory studies of environmental problems and the detection of potentially undesirable environmental constituents at levels below their expected toxicity, thus increasing the support for analytical chemistry in a prominent way by the Environmental Protection Agency (EPA) and other American institutions.
In the 1990s there was a widespread bad conscience about the deleterious effects of chemistry and the collateral effects of analytical methods, due to the use of toxic reagents and solvents and the generation of dangerous wastes. This was the basis of some of the pioneering effort for greening the methods of analysis through the minimization of risks for operators by using mechanized procedures and closed systems. As a result, initiatives like the development of environmentally friendly analytical methods or clean methods were proposed in 1994. The ethical agreement between chemistry and the environment has emerged from the green chemistry movement under the leadership of Paul Anastas, although it was Cathcart who first used the term 'green chemistry'.
In fact, the philosophy of green chemistry can now be considered as the central theory of ecological chemistry. In this framework, analytical chemistry, as a tool to determine the quality of air, water, and soil, can be seen indispensable to demonstrate the side effects of the chemiurgical period. It also provides the data required to establish the development of models for the decomposition of synthetic toxic molecules, in order to reinforce the need for chemical knowledge for the evaluation of environmental risks of the production, transport and use of chemicals. On the other hand, analytical activities can also contribute to damage of ecosystems through the use of toxic reagents and the generation of wastes. The opportunities offered by this discipline must therefore be complemented by a series of commitments to environmental preservation, and by social activities addressed to policy-makers and the general population in order to demonstrate the benefits of chemistry. In short, the use of 'green chemistry' must improve social benefits and avoid collateral damage; this principle should be considered in all fields, including analytical activities. Today, the prestige of our discipline depends heavily on the safety of measurements and the absence of environmental risks.
The increasing social demand for analytical methods and the need for fast, accurate, precise, selective and sensitive methodologies also oblige us to consider the use of reagents that are innocuous, or at least less toxic than those formerly used; to drastically reduce the amounts of samples, reagents and solvents employed; and to minimize, decontaminate and neutralize the wastes generated. For these reasons, a safe and sustainable analytical chemistry must be clearly established from the fundamental, practical and application points of view.
Figure 1.1 shows a schematic evolution of the main objectives of analytical chemistry in the frame of the chemiurgical and ecological paradigms. As this figure shows, the replacement of economic and technological development by the search for an equilibrium between the human race and the biosphere has involved broadening the interest of analysts from the main focus of their methodologies in order to consider the side effects of their practices too. However, in an evolutionary perspective, it is our opinion that good green analytical chemistry must pay attention to the new challenges without renouncing improvements in the basic aspects of analytical methods. We must find an equilibrium between the replacement of toxic reagents by innocuous ones, or the reduction of sample, reagent and solvent consumption, and the preservation or enhancement of the accuracy, sensitivity, selectivity and precision of the methods available. Otherwise we could damage the capacity of analytical chemistry to provide valuable data to support our knowledge of the stability, evolution and damage of ecosystems. For this reason, green analytical chemistry must be considered as an balance between the quality of methods and their environmentally friendly character.
1.2 Environment and Operator Safety: an Ethical Commitment
The avoidance of environmental risks, starting by assuming the operator's safety, is a philosophical principle and a social commitment; it is a prevailing concept of green analytical chemistry. Preserving the quality of air, water and land means thinking of future generations. Avoiding the use of dangerous reagents is the best way to guarantee the safety of users. These two aspects are complementary, and sum up the sustainability of green analytical chemistry.
Previously, the reasons for using greener methods were based on the advantages offered by automation and miniaturization in order to reduce the costs of analysis and also increase laboratory productivity. These were the main reasons for downsizing the scale of methods and pushing new ideas such as flow injection analysis, sequential injection analysis or multicommutation, or developing solvent-free sample preparation techniques such as solid phase extraction, solid phase microextraction, single drop microextraction or stir bar sorptive extraction. However, it is clear that these analytical milestones have a new meaning when considered in the framework of the green analytical chemistry philosophy. In fact, the absence of extra costs in green methodologies is one of their most attractive aspects, because it offers a unique opportunity to be socially honest without sacrificing economic benefits.
When we think about the main strategies that green analytical chemistry can use to avoid environmental side effects (see Figure 1.2), it is evident that there is good correlation between environmental and operator benefits due to the reduction of sample and reagent consumption through automation, miniaturization and on-line detoxification of wastes. The best thing is that the costs are reduced to the acquisition of basic equipment, which is easily offset by the reduced consumption of reagents and the enhancement of laboratory productivity. In terms of the analytical figures of merit, only sensitivity can be affected by the change from batch analysis to the use of automation. However, it is clear that when sample volume is reduced, in-batch selectivity can be enhanced by incorporating the physical and chemical kinetic aspects. It is also evident that the mechanization of analytical methods always improves the repeatability and reproducibility of analytical signals, avoiding operator errors.
However, the most important aspect is that green strategies can offer a new perspective of chemistry to the general public, allowing them to appreciate the important role of chemistry in both prevention and remediation of the environmental pollution, and can also counter the common idea that chemistry itself is the main reason for environmental damage. This approach can be highly beneficial in terms of social support for new developments in chemistry. For this reason, in both teaching and publishing, there is a crucial interest in the incorporation of green terminology and environmental considerations in analytical chemistry today. In order to do this the systematic evaluation of green aspects of new and available methodologies is mandatory. Many efforts have been made to incorporate SWOT (strengths–weaknesses–opportunities–threats) analysis in the evaluation of green alternatives, and to use green pictograms to identify the environmentally friendly character of available methods. As shown in Figure 1.3, these green symbols can contribute to the visibility of efforts towards improving the safety of available procedures.
In fact an extra effort of communication is needed to transfer the environmentally friendly conscience of the scientific community to method users. This is the intention of recent initiatives which can be seen in editorials of journals specifically devoted to green chemistry, like Green Chemistry published by the Royal Society of Chemistry from 1999 or Green Chemistry Letters and Reviews published since 2007 by Taylor & Francis. Special issues of analytical journals have been devoted to green methods, such as those published in February 1995 by The Analyst, issues of Spectroscopy Letters devoted to 'green spectroscopy' in 2009 and Trends in Analytical Chemistry concerning green analytical chemistry published in 2010. It is also important to note the publication in 2010 of two books on green analytical chemistry, that of M. Koel and M. Kaljurand published by the RSC and that of M. de la Guardia and S. Armenta published by Elsevier.
Mary Kirchhoff, in an editorial in the Journal of Chemical Education, has highlighted the importance of education for a sustainable future, emphasizing the positive contributions of chemistry to human health and environmental preservation as the best way to connect with the way society is moving. Probably one reason for the prevalence of the term 'green analytical chemistry' in preference to other descriptions — such as environmentally friendly, sustainable, clean, safe or ecological analytical chemistry — is that the word 'green' is commonly used in the mass media and the general public clearly identify its ethical implications with the sustainability of our activities.
To conclude, Figure 1.4 summarizes these discussions about the relationship between green analytical chemistry, operators and the environment, focusing on the benefits created by green strategies in terms of comfort and safety and introducing the problems of costs.
1.3 Green Chemistry Principles and Green Analytical Chemistry
Although many of the basic developments leading to green analytical chemistry took place in the 1970s and 1980s, the 1990 Pollution Prevention Act in the United States provided a political starting point for the green paradigm. As indicated by Linthorst, who focuses on the EPA and the philosophical principles of green chemistry established by Paul Anastas and co-workers, this was the basis of the green revolution which has involved all aspects of today's chemistry, from synthesis and analytical practices to engineering.
Figure 1.5 shows another diagram of green chemistry principles, emphasizing the special concerns of analytical practice. Only the second principle shown on the figure, 'maximize atom economy', has no evident application in the analytical field. Two principles — avoidance of chemical derivatizations and the use of catalysts — can be directly translated into recommendations for method selection. However, on looking for the analytical consequences of green chemistry principles it is clear that two main activities strongly recommended for the greening of analytical methods are absent — the minimization of sample, reagent and solvent consumption through automation or miniaturization, and the avoidance (as far as possible) of sample treatment. On the other hand, the use of less hazardous, safe reagents, green solvents, easily degraded reagents, or chemicals obtained from renewable sources could be summarized in just one or two recommendations to avoid redundancy.
So, additional efforts must be made to adapt the green chemistry principles to the analytical field. Namiesnik's attempt to establish the priorities of green analytical chemistry is probably a good starting point. He identified four possible routes:
Elimination or reduction of reagents and solvents
Reduction of emissions
Elimination of toxic reagents
Reduction of labour and energy.
Excerpted from Challenges in Green Analytical Chemistry by Miguel de la Guardia, Salvador Garrigues. Copyright © 2011 Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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Meet the Author
Professor Miguel de la Guardia currently holds position as Professor of Analytical Chemistry in Valencia University (Spain). He received his MsSc from Valencia in 1976 and a PhD degree from the same university in 1979 with a thesis about "The use of emulsions in Atomic Spectroscopy". Promoted to Associate Professor in 1985, his current professorship started from 1991. During this time Professor Miguel de la Guardia have been member of a research team with a staff involving Prof. Agustin Pastor (Chromatography studies), Prof. M. Luisa Cervera (Atomic Spectrometry), Prof. Angel Morales (Automation and micro-wave assisted methodologies) and Prof. Salvador Garrigues (Vibrational Spectrometry) and many post-doctoral colleagues, friends and students who have cooperated for the publication of more than 400 research papers in international journals, from which 338 have been correctely included in the ISI web of Science His current research is focused on the automation of analytical methods through multicommutation, sample preparation procedures for both, elemental analysis and speciation, and for chromatography and spectrometry determinations and quantitative vibrational spectrometry in the FTIR, NIR and Raman fields. Other major topics of my research are Chemometrics, Development of green analytical methods and Development of portable spectrometers. Professor Miguel de la Guardia has also supervised 29 PhD thesis and participate in many analytical symposia through the world being invited speaker in France, Germany, Italy, Brazil, Venezuela, Morocco, Turkey, China, Norway, UK, USA, Colombia, Egypt, Uruguay, Argentina, Switzerland, Belgium. He is a member of the editorial board of Spectroscopy Letters (USA), Ciencia (Venezuela), J. Braz. Chem. Soc. (Brazil), having previously been member of the Advisory board of Analytica Chimica Acta from 1995 to 2000. He is currently a consultant of the government of Portugal, Italy, Argentina and China for the evaluation of research proposals and grants and is regularly requested by several journals to act as reviewer.
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