The use of gas chromatography isotope ratio mass spectrometry (GC-IRMS) for compound specific stable isotope analysis is an underutilized technique because of the complexity of the instrumentation and high analytical costs. However stable isotopic data, when coupled with concentration measurements, can provide additional information on a compounds production, transformation, loss, and cycling within the biosphere and atmosphere. A GC-IRMS system was developed to accurately and precisely measure [delta]13C values for numerous oxygenated volatile organic compounds (OVOCs) having natural and anthropogenic sources. The OVOCs include methanol, ethanol, acetone, methyl ethyl ketone, 2-pentanone, and 3-pentanone. Guided by the requirements for analysis of trace components in air, the GC-IRMS system was developed with the goals of increasing sensitivity, reducing dead-volume and peak band broadening, optimizing combustion and water removal, and decreasing the split ratio to the IRMS. The technique relied on a two-stage preconcentration system, a low-volume capillary reactor and water trap, and a balanced reference gas delivery system. Measurements were performed on samples collected from two distinct sources (i.e. biogenic and vehicle emissions) and ambient air collected from downtown Miami and Everglades National Park. However, the instrumentation and the method have the capability to analyze a variety of source and ambient samples. The measured isotopic signatures that were obtained from source and ambient samples provide a new isotopic constraint for atmospheric chemists and can serve as a new way to evaluate their models and budgets for many OVOCs. In almost all cases, OVOCs emitted from fuel combustion were enriched in 13C when compared to the natural emissions of plants. This was particularly true for ethanol gas emitted in vehicle exhaust, which was observed to have a uniquely enriched isotopic signature that was attributed to ethanol's corn origin and use as an alternative fuel or fuel additive. Results from this effort show that ethanol's unique isotopic signature can be incorporated into air chemistry models for fingerprinting and source apportionment purposes and can be used as a stable isotopic tracer for biofuel inputs to the atmosphere on local to regional scales.

Gas chromatography mass spectrometry (GC-MS) has been the technique of choice of analytical scientists for many years. The latest developments in instrumentation, including tandem mass spectrometry (MS-MS) and time-of-flight (TOF) detectors, have opened up and broadened the scope of environmental analytical chemistry. This book summarizes the major advances and relevant applications of GC-MS techniques over the last 10 years, with chapters by leading authors in the field of environmental chemistry. The authors are drawn from academia, industry and government. The book is organized in three main parts. Part I covers applications of basic GC-MS to solve environmental-related problems. Part II focuses on GC-MS-MS instrumentation for the analyses of a broad range of analysis in environmental samples (pesticides, persistent organic pollutants, endocrine disruptors, etc.). Part III covers the use of more advanced GC-MS techniques using low- and high-resolution mass spectrometry for many applications related to the environment, food and industry. - Summarizes the major advances of GC-MS techniques in the last decade - Presents relevant applications of GC-MS techniques - Covers academic, industrial and governmental sectors

The book begins by covering the basic principles of both gas chromatography (GC) and mass spectrometry (MS) to the extent necessary to understand and deal with the data generated in a GC-MS analysis. The focus then turns to the particular requirements created by a direct combination of these two techniques into a single instrumentation system. The data generated and their use are covered in detail. The role of the computer and its specific software receives special attention, especially in the matter of compound identification via mass spectral search techniques. GC-MS-computer instrumentation has reached such a plateau of excellence today that the present commercial systems will not be obsolete for a long time to come. Therefore, a detailed description of these systems is not only informative but is also pertinent to the subject matter of this book. Finally, representative applications and results obtained with GC-MS-computer techniques are presented and chosen in such a way as to permit extrapolation of specific applications to similar problems encountered by the reader. To aid the reader in mastering the subject matter and increase understanding, interpretation problems and suggested readings are included. The format is instructional, informative and application-oriented with material presented in such a way as to be useful to a broad spectrum of people.The book serves as a text in its own right.The software package Gas Chromatography-Mass Spectrometry: A Knowledge Base, by F.A. Settle, Jr. and M.A. Pleva provides rapid access to a wealth of current information in the GC-MS field. Its three diskettes (51/4 inch) allow the user three ways to access: the index mode, the tree mode and a keyword search mode. The package may be purchased separately and is available for the IBM-PC and compatibles.The software provides a valuable supplement to the book.

Praise for Guy P. Brasseur's Atmospheric Chemistry in a Changing World American Meteorological Society "This volume summarizes and integrates more than a decade of atmospheric chemistry research. During the period under consideration, great progress has been made in computing, modeling, and observational techniques, and methods have also improved. Here, suggestions for the highest priority research for the next decade are made, and important information is related regarding impacts on the environment."