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Eingeladener Vortrag
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The phosphorylation of p-tert-butylcalix[8]arene (1) with phosphorus pentachloride and hydrolysis gives intramolecular bridging tert-butylcalix[8]arene triphosphates. The reactivity (esterification, dehydratisation, complexation), the structure (nmr and x-ray), and the stereochemical behaviour of the phosphates will be discussed.
Seabird excrements (guano) have been preserved in the arid climate of Northern Chile since at least the Pliocene. The deposits of marine organic material in coastal areas potentially open a window into the present and past composition of the coastal ocean and its food web. We use the stable isotope composition of nitrogen and carbon as well as element contents to compare the principal prey of the birds, the Peruvian anchovy, with the composition of modern guano. We also investigate the impact of diagenetic changes on the isotopic composition and elemental contents of the pure ornithogenic sediments, starting with modern stratified deposits and extending to fossil guano. Where possible, 14C systematics is used for age information. The nitrogen and carbon isotopic composition of the marine prey (Peruvian anchovy) of the birds is complex as it shows strong systematic variations with latitude. The detailed study of a modern profile that represents a few years of guano deposition up to present reveals systematic changes in nitrogen and carbon isotopic composition towards heavier values that increase with age, i.e. depth. Only the uppermost, youngest layers of modern guano show compositional affinity to the prey of the birds. In the profile, the simultaneous loss of nitrogen and carbon occurs by degassing, and non-volatile elements like phosphorous and calcium are passively enriched in the residual guano. Fossil guano deposits are very low in nitrogen and low in carbon contents, and show very heavy nitrogen isotopic compositions. One result of the study is that the use of guano for tracing nitrogen and carbon isotopic and elemental composition in the marine food web of the birds is restricted to fresh material. Despite systematic changes during diagenesis, there is little promise to retrieve reliable values of marine nitrogen and carbon signatures from older guano. However, the changes in isotopic composition from primary marine nitrogen isotopic signatures towards very heavy values generate a compositionally unique material. These compositions trace the presence of guano in natural ecosystems and its use as fertilizer in present and past agriculture.
Isotope reference materials are needed to calibrate and validate analytical procedures used for the determination of isotope amount ratios, procedurally defined isotope ratios or so-called δ values. In contrast to the huge analytical progress in isotope ratio analytics, the production of isotope reference materials has not kept pace with the increasing needs of isotope analysts. Three representative isotope systems are used to explain the technical and non-technical difficulties and drawbacks, on one hand, and to demonstrate what can be achieved at its best, on the other hand. A clear statement is given that new isotope reference materials are needed to obtain traceable and thus comparable data, which is essential for all kinds of isotope research. The range of available isotope reference materials and δ reference materials should be increased and matrix reference materials certified for isotope compositions or δ values, which do not exist yet, should be provided.
Gravimetric synthetic mixtures of seven enriched, purified cadmium isotope materials were used to determine the correction factors for mass fractionation (MC-TIMS) and mass discrimination (MC-ICP-MS). The isotope abundance ratios determined for various natural cadmium materials represents the isotope composition for natural cadmium materials. Correction of the isotope abundance ratios observed yielded isotope abundances of 106Cd 0.012450(8), 108Cd 0.008884(4), 110Cd 0.124846(16), 111Cd 0.127955(14), 112Cd 0.241110(38), 113Cd 0.122254(22), 114Cd 0.287439(60) and 116Cd 0.075183(32). The newly determined atomic weight of natural cadmium based on SI-traceable evaluation of the isotope abundance ratios is 112.41384(18). The cadmium material designated in the paper as Cd-2211 can be used as an isotope reference material with a δ(114Cd/110Cd)-value of 0. The results obtained show that the uncertainties for the isotope abundances and the atomic weight given as IUPAC values for cadmium are overestimated.
A layer of Sb atoms, implanted with an energy of 400 keV and a nominal dose of 5×1016 atoms/cm2 into a high purity silicon wafer, was certified for its areal density (atoms/cm2) using Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA) and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and for its isotope ratio using INAA and ICP-IDMS. Excellent agreement between the results of the different independent methods was found. In the present work, the measurements of the homogeneity of the areal density of Sb, previously determined with RBS in spots having 1 mm diameter, are improved with synchrotron X-ray fluorescence analysis: Higher precision in even smaller sample spots allows to estimate a reduced inhomogeneity of the whole batch of samples of the order of only 0.4%. Thus the uncertainty of the certified value can further be reduced. Down to fractions of a chip with 0.3×0.4 mm2 area, the areal density is now certified as (4.81±0.06)×1016 Sb atoms/cm2, where the expanded uncertainty 0.06 (coverage factor k=2) corresponds to only 1.2%. The relative merits of the different analytical methods are discussed.
Production of three certified reference materials for the sulfur content in gasoline (petrol)
(2007)
Directive 2003/17/EC of the European Parliament and the European Council stipulates that petrol (gasoline) with a total sulfur content below 10 mg kg-1 must be available in all European Union member states by 2009. Three certified reference materials were produced in support of this directive in a joint effort of the members of the European Reference Materials Initiative (ERM). Two of the materials were made from commercial petrol, while the third one was prepared from a blend of commercial petrols. Relative between-ampule heterogeneity of the materials was quantified and found to be below 2.5%. Potential degradation during storage and dispatch was quantified, and shelf lives based on these values were set. The three materials were characterized by three institutes using different variants of isotope-dilution mass spectrometry. The results from the three institutes were combined, and the final uncertainties of the respective sulfur mass fractions were estimated including contributions from heterogeneity, stability, and characterization. The following mass fractions were derived: ERM-EF211, 48.8 ± 1.7 mg kg-1; ERM-EF212, 20.2 ± 1.1 mg kg-1; and ERM-EF213, 9.1 ± 0.8 mg kg-1.