Search results for " MS"
showing 10 items of 169 documents
Triple Isotope Fractionation Exponents of Elements Measured by MC-ICP-MS—An Example of Mg
2019
In most chemical reactions, stable isotopes are fractionated in a mass-dependent manner, yielding correlated isotope ratios in elements with three or more stable isotopes. The proportionality between isotope ratios is set by the triple isotope fractionation exponent θ that can be determined precisely for, e.g., sulfur and oxygen by IRMS, but not for metal(loid) elements due to the lower precision of MC-ICP-MS analysis and smaller isotopic variations. Here, using Mg as a test case, we compute a complete metrologically robust uncertainty budget for apparent θ values and, with reference to this, present a new measurement approach that reduces uncertainty on θ values by 30%. T…
Zvaigžņotā Debess: 2007/08, Ziema
2007
Latvijas Zinātnes padome, Latvijas Universitāte
Assessment of Five Monazite Reference Materials for U-Th/Pb Dating Using Laser-Ablation ICP-MS
2019
Monazite is a common accessory phosphate mineral that occurs under a wide range of pressure and temperature conditions in sedimentary, metamorphic and igneous rocks. Monazite contains high amounts of Th and U, rendering single monazite grains suitable for in-situ U-Th/Pb dating using laser ablation inductively-coupled mass spectrometry (LA-ICP-MS). Two key aspects of monazite dating that are critical for accurate age data with maximum precision are (i) optimized instrumental conditions to minimize analytical scatter and (ii) a well characterized reference material to ensure the accuracy of the obtained aged. Here, we analyzed five monazite reference materials (USGS 44069, 94-222, MAdel, Moa…
Non-Matrix-Matched Calibration for the Multi-Element Analysis of Geological and Environmental Samples Using 200 nm Femtosecond LA-ICP-MS: A Compariso…
2014
LA-ICP-MS is one of the most promising techniques for in situ analysis of geological and environmental samples. However, there are some limitations with respect to measurement accuracy, in particular for volatile and siderophile/chalcophile elements, when using non-matrix-matched calibration. We therefore investigated matrix-related effects with a new 200 nm femtosecond (fs) laser ablation system (NWRFemto200) using reference materials with different matrices and spot sizes from 10 to 55 μm. We also performed similar experiments with two nanosecond (ns) lasers, a 193 nm excimer (ESI NWR 193) and a 213 nm Nd:YAG (NWR UP-213) laser. The ion intensity of the 200 nm fs laser ablation was much l…
(Table 1) Geochemistry of ODP Site 160-963 sediments
2010
The Mediterranean Sea acts as a miniature ocean with the development of its own conveyor belt. It constitutes an ideal location to study and forecast how the marine environment responds to rapid climatic change. Here we present a palaeoenvironmental study carried out on the sediments of ODP Site 963, recovered in the Sicily Channel, the sill which divides the western from the eastern Mediterranean basin. We focused on the transition between the penultimate glacial (MIS 6) and the last interglacial (MIS 5), between approximately 130 and 115 kyr BP. A novel approach is proposed, taking into account centennial-scale geochemical data on major elements, selected trace elements, and yttrium and R…
(Table 1) Trace element/Ca ratios of Orbulina universa shells from late Neogene Mediterranean samples
2008
A Mediterranean composite sedimentary record was analyzed for Ba/Ca ratios on carbonate shells of Orbulina universa planktonic foraminifer (Ba/Ca)carb providing the opportunity to study and assess the extent of freshwater inputs on the basin and possible impacts on its dynamics during the Tortonian to Recent period. A number of scanning electron microscope analyses and auxiliary trace element measurements (Mn, Sr, and Mg), obtained from the same samples, exclude important diagenetic effects on the studied biogenic carbonates and corroborate the reliability of (Ba/Ca)carb ratios in foraminifera calcite as indicators of seawater source components during the studied interval. A long-term trend…
Relationships between sodium mobility, in-mouth salt and aroma release, and flavour perception : application to model cheeses
2012
The aim of this work is to understand the effects of changes in the composition of model cheeses on mobility, release and perception of flavor molecules (salt, aroma compounds). Six flavoured model cheeses were formulated (3 lipid/protein (L/P) ratios and 2 salt contents). The microstructure and the rheological properties of the model cheeses were characterized respectively by confocal microscopy and by uniaxial compression test. The mobility of sodium ions was analyzed by 23Na NMR. The kinetics of sodium release was followed in water and then in saliva during consumption of the model cheeses. The retronasal release of aroma compounds was followed by nose-space APCI-MS, simultaneously with …
Relationships between sodium mobility, in-mouth salt and aroma release, and flavour perception : application to model cheeses
2012
The aim of this work is to understand the effects of changes in the composition of model cheeses on mobility, release and perception of flavor molecules (salt, aroma compounds). Six flavoured model cheeses were formulated (3 lipid/protein (L/P) ratios and 2 salt contents). The microstructure and the rheological properties of the model cheeses were characterized respectively by confocal microscopy and by uniaxial compression test. The mobility of sodium ions was analyzed by 23Na NMR. The kinetics of sodium release was followed in water and then in saliva during consumption of the model cheeses. The retronasal release of aroma compounds was followed by nose-space APCI-MS, simultaneously with …
Core oligosaccharide of Escherichia coli B—the structure required for bacteriophage T4 recognition
2015
Abstract The structure of Escherichia coli B strain PCM 1935 core oligosaccharide has been investigated by 1H and 13C NMR spectroscopy, MALDI-TOF MS and ESI MSn. It was concluded that the core oligosaccharide is a pentasaccharide with the following structure: ESI MS/MS analysis revealed that the glycine (a minor component) is linked to the →3,7)- l -α- d -Hepp-(1→ residue.
Calcium Carbonate and Phosphate Reference Materials for Monitoring Bulk and Microanalytical Determination of Sr Isotopes
2017
In situ laser ablation analyses rely on the microanalytical homogeneity of reference materials (RMs) and a similar matrix and mass fraction between unknown samples and RMs to obtain reliable results. Suitable carbonate and phosphate RMs for determination of Sr isotope ratios in such materials are limited. Thus, we determined Sr-87/Sr-86 ratios of several carbonate (JCt-1, JCp-1, MACS-1, MACS-3) and phosphate (MAPS-4, MAPS-5, NIST SRM 1400, NIST SRM 1486) international RMs using dissolved samples and two different multi-collector inductively coupled plasma-mass spectrometers (MC-ICP-MS). Our Sr isotope data are in agreement with published data and have an improved measurement precision for s…