Environmental Mass Spectrometry: Emerging Contaminants and Current Issues

摘要

This review covers developments in environmental mass spectrometry over the period of 2002-2003. A few significant references that appeared between January and March 2004 are also included. This review is in keeping with a current approach of Analytical Chemistry to include only 100-200 significant references and to mainly focus on trends in analytical methods. As a result, this review will limit its focus to new, emerging contaminants and environmental issues that are driving most of the current research. Even with a more narrow focus, only a small fraction of the quality research publications could be discussed. Thus, this review will not be comprehensive, but will highlight new areas and only discuss representative papers in the areas of focus. I would welcome any comments you have, in particular regarding this more narrow focus, whether you find it more (or less) useful than a broader approach (richardson.susan@epa.gov). Numerous abstracts were consulted before choosing the best ones to present here. Abstract searches were carried out using the Web of Science. A table of acronyms is provided (Table 1) as a quick reference to the acronyms of analytical techniques and other terms discussed in this review. A table of useful websites is also provided (Table 2). Over the last two years, the overall trends in analytical methods for environmental analysis include an increased application of time-of-flight (TOF), quadrupole-ion trap, and Fourier transform (FT) mass spectrometers; increased use of chiral separations (usually with chiral gas chromatography (GC) or liquid chromatography (LC) columns or using capillary electrophoresis (CE)); more on-line coupling of extraction with separation/detection, such as solid-phase extraction (SPE) or solid-phase microextraction (SPME) coupled with LC/mass spectrometry (MS); increased use of LC/MS/MS and GC/MS/MS; and increased coupling of LC and ion chromatography (IC) with inductively coupled plasma (ICP)MS for inorganic applications. The use of matrix-assisted laser desorption ionization (MALDI)-MS and electrospray ionization (ESI)-MS has also increased for the analysis of microorganisms. Research in this area is now going beyond simple fingerprinting and empirical matching of MALDI or ESI mass spectra to the organisms; papers are reporting increased development of modeling approaches for improving identifications, complete sequencing of protein biomarkers, and techniques to explore the structure and function of these microorganisms. MALDI- and ESI-MS are also increasingly being used to probe the structures of high molecular weight natural organic matter (i.e., humic materials). Previously, mass spectral analysis of humic material was only possible through the use of chemical and thermal degradative techniques, such as pyrolysis-GC/MS, which did not permit the analysis of the original, intact molecule. The availability of MALDI-and ESI-MS, along with the use of high-resolution FT-ion cyclotron resonance (ICR)-MS and MS/MS, is allowing the analysis of intact humic materials for the first time by mass spectrometry. The last two years have also seen a combined approach of using size exclusion chromatography (SEC) to separate/purify molecular weight fractions prior to analysis by ESI-MS; this is designed to address the question about whether humic materials are selectively ionized, creating a low molecular weight bias.