Multidimensional Analytical Techniques in Environmental Research

Regina Duarte, Armando C. Duarte

• Publisher: Elsevier
• Year: 2020
• ISBN:
  9780128188972
• Topic: Physical Sciences
• Subtopic: Analytic Chemistry

Multidimensional Analytical Techniques in Environmental Research is a comprehensive resource on the many multidimensional analytical strategies to qualitatively and quantitatively assess and map the organic and inorganic pollutants in complex atmospheric, water and soil matrices. During the past two decades, the rapidly-evolving field of analytical instrumentation has produced sophisticated multidimensional tools capable of providing unique and in-depth knowledge on the chemical features of complex mixtures from these different environmental matrices. This book brings together the wealth of information in the current literature, assisting in the decision-making process by covering both the fundamentals and applications of these methodologies.

Sections cover the wide variety of multidimensional analytical techniques, including multidimensional solution- and solid-state nuclear magnetic resonance (NMR) spectroscopy, ultrahigh-resolution mass spectrometry (MS), two-dimensional correlation spectroscopy, two-dimensional liquid and gas chromatography and capillary electrophoresis coupled to high-resolution detection techniques, and excitation-emission (EEM) fluorescence spectroscopy assisted by multiway data analysis tools, and the use of synchrotron-radiation-based techniques combined with other spectroscopic approaches to explore and map the speciation of elements.

• Identifies state-of-the-art multidimensional analytical methods for targeted and untargeted profiling of complex mixtures from different environmental matrices (soil, sediment, water, and air)
• Assesses the advantages and limitations of the most modern and sophisticated multidimensional analytical methods in environmental research
• Highlights the current challenges and potential future directions in the application of multidimensional analytical tools to advance the current understanding on the dynamics and fate of environmental pollutants in different environmental matrices

1

Multidimensional analytical techniques in environmental research: Evolution of concepts

Regina M.B.O. Duarte; Armando C. Duarte Department of Chemistry & CESAM, University of Aveiro, Aveiro, Portugal

Abstract

Atmospheric particles, soils, sediments, and dissolved organic matter in aquatic compartments are among the most complex environmental matrices known. To a large extent, the complexity and heterogeneity of these matrices hinder the current understanding of the key processes in the environment. On the quest to mine the desired information, innovative approaches have been developed for the characterization and deconvolution of the complexity of samples at different scales. This chapter sets the scene regarding the development of multidimensional and multiscale hyphenated methods for unraveling complex matrices. It will provide a critical look at the use of a second or third dimension in spectroscopic, spectrometry, and chromatographic methods, and it will identify the most important state-of-the-art multidimensional analytical strategies currently in use for the targeted and untargeted profiling of complex organic mixtures from different environmental matrices. This chapter aims at inspiring the reader to follow multidimensional strategies to solve their analytical and environmental problems.

Keywords

Complex organic mixtures; Natural organic matter; Elemental analysis; Speciation; NMR spectroscopy; High-resolution mass spectrometry; Two-dimensional correlation spectroscopy; EEM fluorescence spectroscopy; Multidimensional chromatography; Synchrotron-based techniques

Acknowledgments

Thanks are due to FCT/MCTES for the financial support to CESAM (UID/AMB/50017/2019) and project AMBIEnCE (PTDC/CTA-AMB/28582/2017), through national funds (OE). FCT/MCTES is also acknowledged for an Investigator FCT Contract (IF/00798/2015).

Challenges in environmental research

Nowadays, most of the environmental challenges are associated with the increased release of pollutants into the air, water, and soil, modifications on the global cycling of nutrients and contaminants, and climate change issues. The advancements made thus far in environmental research have originated either from the need to understand the abovementioned issues or to seek solutions and regulations. Either way, most studies focus on understanding the interactions within and among atmospheric, terrestrial, aquatic, and living compartments of ecosystems. This is, however, an extremely challenging task, mainly due to the variability of those ecosystems and the high degree of heterogeneity, both in terms of composition and concentration, of the samples and analytes of interest taken from the different environmental compartments. This complexity represents a true analytical challenge. It is, therefore, not surprising that the development of new analytical strategies to unravel such complex matrices has occupied a central role in the effort of researchers.

The dramatic development during the past decade in a diverse suite of analytical tools, using a second or third dimension or multiscale hyphenated methods (i.e., separative and detection methods), have contributed to advances in environmental research. These advances include significant improvements in (i) analytical sensitivity and accuracy for the targeted, semitargeted, and untargeted screening of complex organic matrices (e.g., high-resolution mass spectrometry, HR-MS [1–6]); (ii) the use and/or combination of spectroscopic [e.g., one- and two-dimensional (2D) liquid- and solid-state nuclear magnetic resonance (NMR) spectroscopy [7–12], and excitation-emission matrix (EEM) fluorescence spectroscopy [13–16]], HR-MS [17–20], and chromatographic separation (e.g., Ref. [21]) to acquire compositional, geographic, and time evolution information on complex organic structures and interactions; (iii) development of powerful comprehensive multidimensional chromatographic tools for the resolution of complex organic matrices (e.g., Refs. [22–30]); (iv) use of synchrotron radiation-based methods to elucidate the speciation and spatial arrangement of toxic elements and nutrients in complex environmental matrices (e.g., Refs. [31–36]); and (v) development of more “user-friendly” data processing and treatment software to deal with the complexity of multidimensional data gathered from the environmental samples in order to glean the desired information (e.g., Refs. [37, 38]), to name a few of the many. The complementarity and technological advances of these multidimensional analytical tools have been key to allow a wider range of complex environmental matrices to be analyzed, enabling the acquisition of innovative data and transformative advances in environmental research.

This chapter aims to introduce the reader to the underlying concepts that have driven the development and use of sophisticated multidimensional and multiscale hyphenated methods for unraveling complex organic mixtures from different environmental matrices. The focus is on second- and third-dimensional spectroscopic, spectrometry, and chromatographic methods, and how these state-of-the-art multidimensional analytical strategies are being used for the targeted and untargeted profiling of such complex organic mixtures. This is not a comprehensive review on the use of these analytical methodologies but instead a broad overview and an introduction to the subsequent chapters, where the most popular multidimensional analytical techniques used in environmental biogeochemistry research are carefully addressed.

Coping with environmental organic matrices complexity

In recent years, there has been an increasing concern for environmental monitoring and development of new analytical procedures for dealing with the huge number of analytes and tackling the great complexity of environmental samples. These complex organic mixtures exhibit a diversity of constituents with different molecular sizes, structures, and chemical properties, which makes their analysis one of the enduring challenges in analytical chemistry. For example, while solving the chemical structure of high molecular size analytes, such as proteins or other natural polymers, requires exploring the relatively well-organized composition of their smaller molecular subunits (i.e., monomers), the analysis of smaller molecules in a mixture is rather more difficult. In the latter situation, the analyst faces a broad chemical and structural diversity, which requires different types of analyses if aiming at the full structural identification of each organic compound [i.e., elemental composition, spatial structure (i.e., its isomers), and/or spatial configuration]. Nevertheless, not all environmental problems require the full identification of all organic compounds present in a sample. Fig. 1.1 illustrates how different levels of compositional information can be distinguished, depending on the purpose of investigation: (i) functional group analysis, which copes with the highest level of molecular diversity (number of organic compounds, n ≥ 1000) at the expenses of chemical resolution, is typically employed when interested in understanding specific properties of complex organic assemblies (e.g., structural average information [7, 8, 10, 12], chemical processes [9, 39], optical properties [13, 40], and fine-scale spatial arrangement of organic carbon forms [31, 34, 35]); (ii) resolve the chemical composition of complex organic mixtures into different organic components or molecular structures (10 ≥ n ≥ 100) is usually chosen to unraveling the molecular codes [11, 21, 41–45], the organic precursors [20, 46, 47], and reactivity [1, 48, 49] of these highly complex mixtures; (iii) target analysis of molecular organic markers (n ≤ 10) is typically used to accurately quantitate and/or monitoring known formation processes or sources of the target compounds in different environmental matrices [23, 24, 28, 29, 50–54]; and (iv) corresponding to the highest level of chemical resolution, the identification of up to three specific organic compounds (n ≤ 2–3) when studying, for example, unknown formation processes or sources of organic particles in the atmosphere (Ref. [55] and references therein) or identifying emerging organic pollutants in industrial wastewater [56] or freshwater [57].

Fig. 1.1 Levels of organic compositional identification in the analysis of complex mixtures from diverse environmental matrices, highlighting the quantification attained by different advanced analytical techniques (n: number of organic compounds identified and/or measured).

In environmental research, the aim of the analysis and the choice of a fit for purpose analytical methodology are strongly interconnected and should be thoroughly assessed beforehand. Identifying specific organic compounds (known or unknown) in a complex environmental sample (i.e., n ≤ 10 in Fig. 1.1, such as the identification and quantification of organic pollutants in a water sample) is different from a global characterization of the whole environmental sample [...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• 1: Multidimensional analytical techniques in environmental research: Evolution of concepts
• 2: Environmental solution-state NMR spectroscopy: Recent advances, potential, and impacts
• 3: Advanced two-dimensional solid-state NMR spectroscopy and its application in environmental sciences
• 4: High-resolution mass spectrometry strategies for the investigation of dissolved organic matter
• 5: Two-dimensional correlation spectroscopy to assess the dynamics of complex environmental mixtures
• 6: Excitation-emission fluorescence mapping and multiway techniques for profiling natural organic matter
• 7: Multidimensional liquid chromatography and capillary electrophoresis coupled to high-resolution detectors applied to complex environmental samples
• 8: Multidimensional gas chromatography for environmental exposure measurement
• 9: Synchrotron radiation-based spatial methods in environmental biogeochemistry
• Author Index
• Subject Index