Samples isotopic, preparation

Secondary ion mass spectra were measured using a Perkin-Elmer+PHI 3500 instrument. Experiments were carried out with 4 kV Ar ions at beam currents of 3 and 300 nanoamps. Spectra were measured to at least 500 daltons (d). Samples were prepared in the manner used for the XPS studies. For measurements on the pure complexes, sample charging occurred, as evidenced by the inability to record secondary ion mass spectra. To reduce charging, a low energy electron beam (50-400 eV) was rastered across the sample during SIMS analysis. Positive and negative ion SIMS spectra were recorded however, only positive ion spectra are of interest for this discussion. In the spectra only unipositive ions were detected, so that the mass numbers detected correspond to combinations of the various isotopes of the elements in the ion. Thus an ion at m/z 17 d is assigned to... 

Samples were prepared for Cu isotope analysis on the Multicollector Inductively-Coupled Plasma Mass Spectrometer (MC-ICPMS) at University of Arizona. The Cu-rich samples were loaded and dissolved in pure HNO3 and the Cu-poor samples were loaded and dissolved in a mixture of HCI and HNO3, Chromatographic separation of the Fe and Cu ions was deemed necessary for the Cu-rich samples. The diluted solutions were injected into the MC-ICPMS using a microconcentric nebulizer. Samples were run numerous times to increase precision. The Cu isotope ratios are reported in conventional per mil notation, relative to the NIST 976 standard. Mass bias was also accounted for by bracketing methods with the NIST 976 standard. 

Analytical nncertainty for hydrogen isotope measnrements is nsually in the range 0.5 to 5%c depending on different sample materials, preparation techniques and laboratories. 

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. 

For product, phosphate 5, changes of 13C content were analysed for acyclic methylene carbon with signal of one methyl group as a reference. Samples were prepared for low conversion (0.1-0.2) and full conversion. For low conversion of product (F<0.3) the isotope effect can be calculated from the formula 42... 

Using the method of isotope substitution, it is possible to obtain partial pair correlation functions experimentally. Two isotopically different samples were prepared at c = 0.1 M, one where all the hydrogen in the butylammonium chains was ordinary II and one where they were entirely deuterated, to make use of the large difference in scattering... 

Fig. 5. Basic equipment for measuring an emission Mdssbauer spectrum. The sample is prepared with a radioactive isotope and used as the source.

Analysis of Spiked Fecal Samples. To simulate fecal samples taken from subjects receiving oral doses of stable isotopes, 54-Fe- and 57Fe-spiked fecal samples were prepared by adding known amounts of the enriched stock solutions of each isotope to aliquots of a homogenized, unenriched, pooled fecal sample. 

Silverman M. P. and Oyama V. 1. (1968) Automatic apparatus for sampling and preparing gases for mass spectral studies of carbon isotope fractionation during methane metabolism. Anal. Chem. 40, 1833-1877. 

Here is how SAL works Samples are received in a reception and storage room, then routed to the appropriate wet chemical analysis laboratory. There, they are analysed for uranium, thorium or plutonium content, and purified aliquots (portions of the sample) are prepared for the isotopic analysis of three elements. Isotopic analyses are performed routinely by mass spectrometry, and radiometric techniques are used for back-up. Emission spectrography serves to detect the presence of impurities which could interfere with the measurements and thus distort the results of the chemical and isotopic analysis of uranium, thorium and plutonium. Complex calculations and quality checks are performed on minicomputers, which are connected in a network to a central laboratory mini-computer. A central laboratory data system stores and provides analytical reports and enables the quality of the analyses and the status of the flow of samples through the laboratory at any time to be monitored. 

To elucidate the isotope effect on superconductivity, we have studied potassium-doped K3 C(jo and samples were synthesized by heating stoichiometric amounts of solvent-free C o and Cso with K metal (3 1, K Cso) in sealed quartz tubes (10" Torr) typically, 1-2 mg of was used. The temperature was ramp from 200 to 400 C over a 1-week period during the reaction. " Kj Cjo and K3 C4o samples were prepared simultaneously in the same furnace to minimize differences due to the preparative conditions. 

N NMR spectroscopy was used to study the tautomerism of adenine derivatives enriched by the N-15 isotope." These enriched samples were prepared as probes for further biochemical studies. While tautomeric mixtures of N -H and N -H were reported for adenine and 2-MeS-adenine based on the " N NMR spectra, an N -H species was suggested for the solution of S-Br-adenine. These observations were supported by quantum chemical calculation of the individual tautomeric forms for isolated molecules and for the inclusion of solvent effects (both continuum and discrete models). 

The methane gas samples were prepared for Isotopic analyses with the system Illustrated In Figure 1. Preparation Involves gas chromatographic (GC) separation of methane from other gases followed by combustion to and water In a vacuum line. 

A more quantitative analysis of the extent of phase separation may be obtained by using the technique of isotopic replacement. Two samples are prepared having the same structure except that the atoms of an element found in one sample have been replaced by an isotope in the other. In this work, this is accomplished by hydrating samples with mixtures of H2O and D2O of various proportions. For samples that have two phase structures the ratio of SANS intensities is given by ... 

Acetone and methanol (A.R. grade) were used without further purification. tert-Butyl alcohol (BDH) was dried over CaO, distilled under vacuum into an ice bath, and recrystallized before use. Absolute ethyl alcohol was dried over CaO and redistilled. Methyl iodide (Baker and Adamson) was singly distilled. Research grade ethylene (Matheson, Ltd.) and acetone-D6 (99.5% D, Stohler Isotope Chemicals) were used as received. Deaerated samples were prepared either in the vapor phase in a 5-liter flask or distilled directly into the irradiation chamber from the pure liquid stored in a tube. 

Four supported nickel catalysts NifCr203, NijSi02, NifMgO and NilZr02 were investigated by Isotopic Transient Kinetics Method [2]. The catalyst samples were prepared by coprecipitation method. B.E.T. surface area and metal dispersion were measured by krypton adsorption and hydrogen chemisorption, respectively [3, 4]. The main measured values of the metallic surface area and the total surface area of the catalysts are reported in Table 1. 

In conclusion, considerable discrepancy afflicts reported data on loss of mercury from samples during preparation and digestion. It is, thus, important to adapt the procedure to real samples and to carefully evaluate recovery, matrix effects, and detection limits for these samples. Mostly, such tests are carried out on spiked samples, but a more distinguished approach is to study the recovery through the different steps of the procedure by use of radioactive mercury isotopes. The most reliable data should be those obtained on samples, in which the mercury has been incorporated in vivo (e.g. Clarkson and Greenwood, 1970 LaFleur, 1973 Stein et al., 1974 Iyengar et al., 1978 Stuart, 1978a Semu et al., 1985). 

The preparation of the fish extracts and the verification of their homogeneity and stability were carried out by the Danish Isotope Centre and the National Food Agency (Soborg, Denmark). The aqueous solutions were prepared at the Kemforschungsanlage (Jiilich, Germany), whereas the mussel and tuna samples were prepared at the Environment Institute of the EC Joint Research Centre of Ispra (Italy). 

The sample is then gravimetrically spiked with an isotopic analogue of the analyte (this analogue is termed the spike) such that the spike concentration matches the prior estimate of the natural analyte concentration in the sample. To prepare a sample solution blend, extraction (organic analysis) or acid mineralisation (inorganic analysis), followed by any clean-up stages necessary is carried out. 

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