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Eingeladener Vortrag
- nein (3)
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.
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.
The stable carbon and nitrogen isotopic composition of urine and milk samples from cattle under different feeding regimes were analysed over a period of six months. The isotope ratios were measured with isotope ratio mass spectrometry (IRMS). The δ13C values of milk and urine were dependent on different feeding regimes based on C3 or C4 plants. The δ13C values are more negative under grass feeding than under maize feeding. The δ13C values of milk are more negative compared to urine and independent of the feeding regime. Under grass feeding the analysed milk and urine samples are enriched in 13C relative to the feed, whereas under maize feeding the 13C/12C ratio of urine is in the same range and milk is depleted in 13C relative to the diet. The difference between the 15N/14N ratios for the two feeding regimes is less pronounced than the 13C/12C ratios. The δ15N values in urine require more time to reach the new equilibrium, whereas the milk samples show no significant differences between the two feeding regimes.
The present work describes the development of an existing TIMS procedure to a reference procedure for low sulfur concentration measurements in fossil fuels. With this enhanced procedure SI-traceable sulfur mass fractions below 10 mg kg-1 can be obtained. The achieved detection limit is approximately 0.2 mg kg-1. The procedure was validated by certified reference materials. The procedure was already applied to candidate reference materials and to samples analysed within projects of the Comité Consultatif pour la Quantité de Matière CCQM.
Additionally the influence of the isotopic composition on the results and its corresponding uncertainty was studied. Reference data published in the literature on the isotopic composition of sulfur were assessed.