Knowledge Base

Goal: Shorted text: Quantitative reconstruction of paleodiet carbon isotope analysis in hypsodont tooth enamel requires a precise knowledge of the isotopic enrichment between dietary carbon and carbon from enamel apatite (εD–E), as well as timing and duration of the mineralization process. High resolution sampling and stable carbon isotope analysis of breath CO2 following a diet-switch showed that 70–90% of dietary carbon had turned over in < 24 h.The changes in diet were recorded in all molars. Portions of enamel in equilibrium with dietary carbon were used to calculate εD–E values. Animals on grass silage diets had values similar to previous observations, whereas animal switched to pelleted corn diets had values ca. 4‰ lower, a pattern consistent with lower methane production observed for animals fed concentrate diets. Our results demonstrate that they can provide useful information about dietary variability if the mineralization process is taken into account.

Goal: Normalization of stable isotope data is important for meaningful inter-laboratory comparisons of data, especially for waters. As a result, large, systematic errors may arise in continuous flow applications without correction, whereas normalization to the VSMOW/SLAP scale can facilitate inter-laboratory comparison and can be accomplished by a simple procedure. Delta values for these standards, as analyzed, are plotted against the calibrated values and a linear regression is performed. The resulting equation is applied to unknown samples to achieve the normalization. The one-sigma [1sigma] standard deviation for replicate samples by this normalization method using a Gas Benchll should be

Goal: A new procedure for the determination of carbon dioxide (CO2) 13C/12C isotope ratios, using direct injection into a Gas Bench/isotope ratio mass spectrometry system, has been developed to improve isotopic methods devoted to the study of the authenticity of sparkling drinks. It has been demonstrated that the addition of C4 sugar to semi-sparkling wine (aguja) and industrial CO2 addition to sparkling wine (cava) or water can be detected. The new procedure has advantages over existing methods in terms of analysis time and sample treatment. In addition, it is the first isotopic method developed that allows 13C/12C determination directly from a liquid sample without previous CO2 extraction. No significant isotopic fractionation was observed nor any influence by secondary compounds present in the liquid phase.

Goal: The measurement of the D/H ratio of water is one of the most important pplications of isotope ratio massspectrometers. Very diverse applications, ranging from studies of variations in natural abundance in the hydrologic cycle to authenticity control of beverages or the use of D-enriched tracers in human and animal metabolic studies, demand a general analytical solution, which provides high precision/ high accuracy/high throughput analysis of D/H in an enormous range of aqueous substrates. With the Gas Bench II, water samples > 200 μL can be routinely analyzed with a precision and accuracy < 1 ‰.

Goal: The measurement of the 18O/16O ratio of water is one of the most important applications of isotope ratio mass spectrometry. The measurement of the 18O/16O ratio of water is one of the most important applications of isotope ratio mass spectrometry.In CO2-water equilibration, a small amount of CO2 in the headspace of a sample vial is isotopically equilibrated with the water entrained in a liquid sample. The very small amount of CO2 in the headspace ensures complete transfer of the 18O information during equilibration (CO2/H2O < 1:3000). With the Gas Bench II, water samples < 200 μl or less can be routinely analyzed to a precision and accuracy of < 0.06 ‰.

Goal: The Thermo Scientific Gas Bench II with the Carbonate-Option, an autosampler assisted sample preparation and loop injection interface, offers a fast and flexible alternative using modern continuous flow technology coupling to the ThermoScientific isotope ratio mass spectrometers DELTA V Advantage, DELTA V Plus and 253 Plus. The Gas Bench II in carbonate mode uses the principle of individual acid baths. Laboratories have shown that at least 80 samples per day (including 14 standards for quality control) can be processed in routine operation. An overall precision of 0.08 ‰ for δ18O and of 0.06 ‰ for δ13C or better has been achieved and accurate measurements of samples containing in excess of 100 μg of carbonate.

Goal: The isotopic composition of DOM and DOC can now be measured by the Thermo Scientific LC IsoLink, the on-line coupling of a liquid chromatograph with an isotope mass spectrometer. With the LC IsoLink™ interface, two approaches are possible: DOC δ13C can be measured either by direct flow injection of water samples (as well as of fractions isolated off-line from larger volumes of water) or, alternatively, for on-line separation of DOM fractions size exclusion chromatography (SEC) for instance can be applied.

Goal: For irm-LC/MS the Thermo Scientific LC IsoLink interface closes this gap in referencing. A direct flow injection mode for sub-μg bulk materials (μ-EA mode) is available in addition to the compound specific analysis using HPLC separation. This direct injection mode is a fast and precise analysis of all water soluble materials. It enables the analysis of reference material with unmatched sensitivity and speed. Reference material can be injected into the sample loop of a six-port valve which is located after the HPLC column. The reference can be introduced on trace before, in-between or after the eluting target compounds or just for a extremely fast and simple comparison of bulk materials.

Goal: The new Thermo Scientific LC IsoLink interface enables the on-line coupling of a liquid chromatograph to a stable isotope ratio mass spectrometer. It significantly reduces the preparation steps and the analysis time. We present an analytical method for the isotope ratio analysis of organic acids in different plants extracts. First results are reported and discussed.

Goal: Isotope ratio monitoring-LC/MS (irm-LC/MS) with the Thermo Scientific LC IsoLink allows determination of 13C/12C ratios of individual amino acids without derivatization, eliminating all of the possible errors, limitations, and time requirements of derivatization. For amino acids water is the best solvent; HPLC columns are available on which the separation of amino acids can be performed with an aqueous mobile phase. The LC IsoLink offers new access to 13C-tracer experiments which investigate amino acid and protein metabolism.

Goal: With the development of the Thermo Scientific LC IsoLink interface, compounds can now be separated by HPLC and analyzed online for their individual 13C/12C ratios by isotope ratio MS. Here we report progress towards a method for HPLC separation of hydrolyzed RNA and determination of the carbon isotopic composition of the monomers.

Goal: This study compares and contrasts the ability to classify individuals into different grouping factors through either bulk isotope ratio analysis or amino-acid-specific isotope ratio analysis of human hair. Using LC–IRMS, we measured the isotope ratios of 14 amino acids in hair proteins independently, and leucine/isoleucine as a co-eluting pair, to provide 15 variables for classification.Multivariate analysis confirmed that the essential amino acids and non-essential amino acids were mostly independent variables in the classification rules, thereby enabling the separation of dietary factors of isotope intake from intrinsic or phenotypic factors of isotope fractionation. Multivariate analysis revealed at least two potential sources of non-dietary factors influencing the carbon isotope ratio values of the amino acids in human hair: body mass index (BMI) and age. These results provide evidence that compound-specific isotope ratio analysis has the potential to go beyond region-of-origin or geospatial movements of individuals—obtainable through bulk isotope measurements—to the provision of physical and characteristic traits about the individuals, such as age and BMI. Further development and refinement, for example to genetic, metabolic, disease and hormonal factors could ultimately be of great assistance in forensic and clinical casework.

Goal: A novel procedure was established for the simultaneous characterization of wine glycerol and ethanol 13C/12C isotope ratio, using liquid chromatography/isotope ratio mass spectrometry (LC-IRMS). Several parameters influencing separation of glycerol and ethanol from wine matrix were optimized. Results obtained for 35 Spanish samples exposed no significant differences and very strong correlations (r = 0.99) between the glycerol 13C/12C ratios obtained by an alternative method (gas chromatography/isotope ratio mass spectrometry) and the proposed new methodology, and between the ethanol 13C/12C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The accuracy of the proposed method varied from 0.01 to 0.19 permil, and the analytical precision was better than 0.25 permil. The new developed LC-IRMS method it is the first isotopic method that allows 13C/12C determination of both analytes in the same run directly from a liquid sample with no previous glycerol or ethanol isolation, overcoming technical difficulties associated with complex sample treatment and improving in terms of simplicity and speed.

Goal: The measurement of the carbon isotopic composition (delta13C) of dissolved inorganic carbon (DIC) in natural systems has provided a tool for examining a variety of processes, from net primary production to anthropogenic signatures of CO2 uptake in the oceans. Over the past decade, new delta13C-DIC methods have steadily decreased the sample analysis time and volumes for this measurement. The development of a new interface capable of inline acidification and extraction of CO2 from a liquid stream (LC-Isolink™) provides breakthroughs in sample size, ease of sample handling, and speed of analyses. Typical sample size injections of 25 microL provide precision and accuracy of 0.04‰, comparable to that obtained by off-line extractions/dual inlet analyses on much larger samples.