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A new analytical method is proposed for measuring the deuterium to hydrogen ratio (D/H) of non-stoichiometric water in hydrous minerals via pyrolysis facilitated gas-chromatography-isotope ratio mass spectrometry (GC-IRMS). Previously published analytical methods have reported a poorly understood nonlinear dependence of D/H on sample size, for which any accurate correction is difficult. This sample size effect been variously attributed to kinetic isotope fractionation within the mass spectrometer and peripheral instruments, ion source linearity issues, and an unstable H_3^+-factor or incorrect H_3^+-factor calculations. The cause of the sample size effect is here identified by examinations of individual chromatograms as well as bulk data from chromatographic peaks. It is here determined that it is primarily an artifact of the calculations employed by the manufacturer's computer program, used to both monitor the functions of the mass spectrometer and to collect data. Ancillary causes of the sample size effect include a combination of persistent background interferences and chromatographic separation of the isotopologues of molecular hydrogen. Previously published methods are evaluated in light of these findings. A new method of H_3^+-factor and D/H calculation is proposed which makes portions of the Isodat software as well as other published calculation methods unnecessary. Using this new method, D/H is measured in non-stoichiometric water in chert from the Cretaceous Edwards Group, Texas, as well as the Precambrian Kromberg Formation, South Africa, to assess hydrological conditions as well as to estimate the maximum average surface temperature during precipitation of the chert. Data from Cretaceous chert are consistent with previously published data and interpretations, based upon conventional analyses of large samples. Data from Precambrian chert are consistent with maximum average surface temperatures approaching 65°C during the Archean, instead of the much lower temperatures derived from erroneous methods of sample preparation and analysis. D/H is likewise measured in non-stoichiometric water in silicified basalt from the Precambrian Hooggenoeg Complex, South Africa. Data are shown to be consistent with D/H of the Archean ocean similar to present day values.
The isotope dilution mass spectrometry (IDMS) technique is well known and widely reported in the literature. However, its application can present considerable difficulties with regard to obtaining reliable results. Produced jointly by the Royal Society of Chemistry's Analytical Methods Committee and the Valid Analytical Measurement (VAM) programme, the aim of this book is to provide a simplified yet robust methodology, together with adequate guidance, to enable laboratories wishing to use the technique to obtain reliable data. The methodologies, for inorganic and organic mass spectrometry, which use exact and approximate matching, are illustrated with worked examples and clear diagrammatic representations. A comprehensive glossary of terms, references to key publications and an extensive IDMS bibliography are also provided. Clear and comprehensive in coverage, Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS) will provide valuable assistance to a wide variety of analytical chemists interested in applying the IDMS technique to their own measurement applications.
This two-volume reference serves as a handbook containing a wealth of information for all isotope chemists working in a wide range of disciplines including anthropology to ecology; drug detection methodology to toxicology; nutrition to food science; and the atmospheric sciences to geochemistry.Complementing the first volume, Volume II includes matters that are not strictly confined to the analytical techniques themselves, but relate to analysis of stable isotopes, such as the views on the development of mass spectrometers, isotopic scales, standards and references, and directives for setting up a laboratory.ALSO AVAILABLE:Volume I: Dec. 2004, 0444511148/9780444511140, $176.00Volume I and II (set): Oct. 2007, 0444511164/9780444511164, $205.00 - Presents an encyclopedic overview of stable isotope analytical techniques in an objective way - Includes descriptions of methods and diagrams of analytical devices - Addresses how older techniques formed the basis for present-day techniques, which can be useful in constructing modern analytical systems - Completments Volume I of the set
The use of Compound-specific Stable Isotope Analysis (CSIA) is increasing in many areas of science and technology for source allocation, authentication, and characterization of transformation reactions. Until now, there have been no textbooks available for students with an analytical chemical background or basic introductory books emphasising the instrumentation and theory. This book is the first to focus solely on stable isotope analysis of individual compounds in sometimes complex mixtures. It acts as both a lecture companion for students and a consultant for advanced scientists in fields including forensic and environmental science. The book starts with a brief history of the field before going on to explain stable isotopes from scratch. The different ways to express isotope abundances are introduced together with isotope effects and isotopic fractionation. A detailed account of the required technical equipment and general procedures for CSIA is provided. This includes sections on derivatization and the use of microextraction techniques in GC-IRMS. The very important topic of referencing and calibration in CSIA is clearly described. This differs from approaches used in quantitative analysis and is often difficult for the newcomer to comprehend. Examples of successful applications of CSIA in food authenticity, forensics, archaeology, doping control, environmental science, and extraterrestrial materials are included. Applications in isotope data treatment and presentation are also discussed and emphasis is placed on the general conclusions that can be drawn from the uses of CSIA. Further instrumental developments in the field are highlighted and selected experiments are introduced that may act as a basis for a short practical course at graduate level.
(Parent with price) Volume I contains subjective reviews, specialized and novel technique descriptions by guest authors. Part 1 includes contributions on purely analytical techniques and Part 2 includes matters such as development of mass spectrometers, stability of ion sources, standards and calibration, correction procedures and experimental methods to obtain isotopic fractionation factors.Volume II will be available in 2005.
Isotope Ratio Mass Spectrometry of Light Gas-Forming Elements explores different methods of isotope analysis, including spark, secondary ion, laser, glow discharge, and isotope ratio mass spectrometry. It explains how to evaluate the isotopic composition of light elements (H, C, N, O) in solid, liquid, and gaseous samples of organic and inorganic substances, as well as: Presents a universal, economical, simple, and rapid technique for sample preparation of organic substances to measure the isotopic composition of carbon Describes how to determine microbial mineralization of organic matter in soil and the effect of exogenous substrates on environmental sustainability Examines use of the isotopic composition of n-alkanes from continental vegetation to study the paleoclimate and plant physiology Proposes a systematic approach to identifying tobacco areas of origin and tobacco products based on data from the isotopic composition of light elements Discusses ways to detect doping drugs and suggests results assessment criteria based on determining reference intervals for endogenous markers Reviews methods of release of gases from inclusions of rocks and minerals for further implementation of isotope mass spectrometric analysis Considers use of optical isotope analyzers for determining the isotopic composition of carbon in CO2 and of hydrogen and oxygen in water Providing a complete picture of the latest advancements in the field, Isotope Ratio Mass Spectrometry of Light Gas-Forming Elements aids readers from a variety of disciplines in identifying the fundamental processes in biological, ecological, and geological systems and in revealing the subtle features of many physicochemical processes and chemical transformations.
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.
Experimental Analysis of Enzyme Mechanism Using Isotope Effects, Volume 596, the latest release in the Methods in Enzymology series, continues the legacy of this premier serial with quality chapters authored by leaders in the field. Chapters in this comprehensive update include Measurement of enzyme binding isotope effects, Chemical ligation and isotope labeling to locate dynamic effects, Measurement of heavy enzyme isotope effects, Extracting kinetic isotope effects from a global analysis of reaction progress curves, KIE of metabolic flux and enzymes, Solvent and Primary KIE on Flavin Enzymes, and The Rapid Determination of Primary Deuterium Isotope Effects on Enzyme-Catalyzed Proton Transfer at Carbon in 50/50 HOH/DOD. Readers who are interested in applying or understanding this research will find useful methods currently used for measuring isotope effects on solution and enzyme reactions. Written by pioneers of modern isotope effect research Is the only collection of modern kinetic isotope effect methods currently available
This work provides detailed coverage of the applications of proven spectometric techniques in soil science. It presents analytical approaches important in the study of pool sizes and the dynamics of macro- and micronutrients, the structure and function of soil organic matter, and the co-evolution of soils, plant communities and climate. Interdisciplinary perspectives from soil science, ecology, geology, chemistry, biogeochemistry, agronomy and physics, are offered.
The Encyclopedia is a complete and authoritative reference work for this rapidly evolving field. Over 200 international scientists, each experts in their specialties, have written over 330 separate topics on different aspects of geochemistry including geochemical thermodynamics and kinetics, isotope and organic geochemistry, meteorites and cosmochemistry, the carbon cycle and climate, trace elements, geochemistry of high and low temperature processes, and ore deposition, to name just a few. The geochemical behavior of the elements is described as is the state of the art in analytical geochemistry. Each topic incorporates cross-referencing to related articles, and also has its own reference list to lead the reader to the essential articles within the published literature. The entries are arranged alphabetically, for easy access, and the subject and citation indices are comprehensive and extensive. Geochemistry applies chemical techniques and approaches to understanding the Earth and how it works. It touches upon almost every aspect of earth science, ranging from applied topics such as the search for energy and mineral resources, environmental pollution, and climate change to more basic questions such as the Earth’s origin and composition, the origin and evolution of life, rock weathering and metamorphism, and the pattern of ocean and mantle circulation. Geochemistry allows us to assign absolute ages to events in Earth’s history, to trace the flow of ocean water both now and in the past, trace sediments into subduction zones and arc volcanoes, and trace petroleum to its source rock and ultimately the environment in which it formed. The earliest of evidence of life is chemical and isotopic traces, not fossils, preserved in rocks. Geochemistry has allowed us to unravel the history of the ice ages and thereby deduce their cause. Geochemistry allows us to determine the swings in Earth’s surface temperatures during the ice ages, determine the temperatures and pressures at which rocks have been metamorphosed, and the rates at which ancient magma chambers cooled and crystallized. The field has grown rapidly more sophisticated, in both analytical techniques that can determine elemental concentrations or isotope ratios with exquisite precision and in computational modeling on scales ranging from atomic to planetary.