Oxygen isotopes preparation

Marino, B.D. and DeNiro, M.J. 1987 Isotopic analysis of archaeobotanicals to reconstruct past climates Effects of activities associated with food preparation on carbon, hydrogen and oxygen isotope ratios of plant cellulose. Journal of Archaeological Science 14 537-548. 

This equation predicts a value of 26.8%ofor the zebra at Turkana assuming an average value of 6%o for Lake Turkana water. This predicted value is l%o less than the actual value of 27.8%o. Given the variation in methods of sample preparation and analysis, variation between bone and tooth enamel (Stuart-Williams and Schwarcz 1997), and uncertainty in surface water oxygen isotopic composition, these values are extraordinarily close. Alternatively, if the equation is solved for using the actual value of the Turkana zebra. 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

Wiechert U, Hoefs J (1995) An exdmer laser-based microanalytical preparation technique for in-situ oxygen isotope analysis of sUicate and oxide minerals. Geochim Cosmochim Acta 59 4093 101... 

A literature project. Until the 1960s, dinosaurs were thought to be cold-blooded animals, which means they could not regulate their body temperature. Reference 1 describes how the l8O/l60 ratio in dinosaur bones suggests that some species were warm blooded. Find reference 1, preferably at http //pubs.acs.org/ac if your institution has an electronic subscription to Analytical Chemistry. Explain how the 180/l60 ratio implies that an animal is warm or cold blooded. Explain the criteria that were used to determine the likelihood that l80/l60 in bone phosphate was altered after the dinosaur died. Describe how bone samples were prepared for analysis of oxygen isotopes and state the results of the measurements. 

Krot A. N., McKeegan K. D., Huss G. R., Liffman K., Sahijpal S., Hutcheon I. D., Srinivasan G., Bischoff A., and Keil K. (2003a) Aluminum-magnesium and oxygen isotope study of rehct Ca-Al-rich inclusions in chondrules. Earth Planet. Sci. Lett, (in preparation). 

Krot A. N., Libourel G., and Chaussidon M. (2003c) Oxygen isotopic compositions of chondrules in CR chondrites. Meteorit. Planet. Sci. (in preparation). 

As already indicated, a special problem with esters is their preparation from two natural precursor molecules by a chemical ester synthesis. Such products have to be labelled nature-identical. For an interesting positional H-NMR study on ethyl butyrate from enzymatic esterification of beet ethanol with butyric acid from milk see [317]. Another chance to detect a corresponding adulteration would be a positional carbon and oxygen isotope analysis of the ester components. Isotope effects on the esterification reaction in question seem to influence characteristically the 8-values of the atoms involved, and hence form a basis for the origin assignment of these compounds (for further details see 6.2.2.4.4). 

Oxygen isotopes in ancient human skeletal remains are found in both bone and tooth enamel. Samples for the analysis of human skeletal remains are normally taken from dental enamel due to conditions of preservation and resistance to diagenesis. The hydroxyapatite mineral, a primary component of enamel, contains oxygen, in both phosphate groups (POp and carbonates (CO ). Phosphate and carbonate produce comparable results for oxygen isotope ratios, but less sample is needed for carbonate, preparation is less demanding, and results between laboratories are more comparable. 

Stable carbon and oxygen isotopes of the different diagenetic carbonates were determined in 22 sandstone samples, which were selected after careful optical and cathodoluminescence examination. Samples in which contamination caused by allo-chems or mixtures of different textural types of calcite (both easily recognized by optical petrography and cathodoluminescence) were not considered for isotopic analysis. The Kiel system for calcite sample preparation was used, and calcite was reacted with anhydrous phosphoric acid at 25°C under vacuum for 2 h, the produced COj was... 

Compston W, Epstein S (1958) A method for the preparation of carbon dioxide from water vapor for oxygen isotopic analysis. EOS Trans Am Geophys Union 39 511 Craig H, Horn B (1968) Relationships of deuterium, oxygen-18, and chlorinity in the formation of sea ice. EOS Trans Am Geophys Union 216... 

Muller J (1995) Oxygen isotopes in iron (111) oxides A new preparation line mineral-water fractionation factors and paleo-environmental considerations. Isotopes Environ Health Stud 31 301-302 Nahr T, Botz R, Bohrmarm G, Schmidt M (1998) Oxygen isotopic composition of low-temperature authigenic clinoptilolite. Earth Planet Sci Lett 160 369-381... 

Crowson RA, Showers WJ, Wright EK, Hoering TC (1991) Preparation of phosphate samples for oxygen isotope analysis. Anal Chem 63 2397-2400... 

This chapter details the technical procedures used to prepare and analyze lake sediment samples for cellulose carbon and oxygen isotope composition, considers important factors in the interpretation of cellulose isotope data, briefly highlights key results from recent applications, and outlines future research needs and directions. 

Methods for lake sediment sample preparation for cellulose carbon and oxygen isotope analyses have been developed at the University ofWaterloo - Environmental Isotope Laboratory (UW-EIL), (Heemskerk Diebolt, 1994 Edwards et al, 1997 Elgood et al., 1997). 

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