Search results for "ISOTOPE"

Profiling of RNA modifications by multiplexed stable isotope labelling

2014

The combination of (15)N/(13)C stable isotope labelling (SIL) and LC-MS/MS revealed a total of 52 modifications in RNA from E. coli and yeast, including 10 previously undescribed modifications. Two modifications, N-ribosylnicotinamide and 2-methylthioadenosine, were newly detected in species hitherto thought not to contain these modifications.

Tracing anthropogenic thallium in soil using stable isotope compositions.

2014

Thallium stable isotope data are used in this study, for the first time, to apportion Tl contamination in soils. In the late 1970s, a cement plant near Lengerich, Germany, emitted cement kiln dust (CKD) with high Tl contents, due to cocombustion of Tl-enriched pyrite roasting waste. Locally contaminated soil profiles were obtained down to 1 m depth and the samples are in accord with a binary mixing relationship in a diagram of Tl isotope compositions (expressed as e(205)Tl, the deviation of the (205)Tl/(203)Tl ratio of a sample from the NIST SRM 997 Tl isotope standard in parts per 10(4)) versus 1/[Tl]. The inferred mixing endmembers are the geogenic background, as defined by isotopically l…

Organic matter quantity and quality, metals availability and foraminiferal assemblages as environmental proxy applied to the Bizerte Lagoon (Tunisia)

2016

International audience; This study analyzes the benthic trophic state of Bizerte Lagoon (Tunisia) based on the total organic matter and the bioavailability of biopolymeric carbon including proteins (PTN), carbohydrates (CHO), lipids (LIP), chlorophyll a, as well as bacteria counts. The overall simultaneously extracted metals (SEM), and acid volatile sulfides (AVS) as well as the SEM/AVS ratio indicative of the toxicity of the sediments also were analyzed aiming to study their impact in the dimension, composition and structure of both dead and living benthic foraminiferal assemblages.In the studied sites TOC content is relatively high and the PTN/CHO values indicate that they can be consider…

Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China

2005

The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively -29.8 per thousand to -26.0 per thousand and 1.6 per thousand-5.5 per thousand in the flood season (July), while they were -27.3 per thousand to -25.6 per thousand and 1.7 per thousand-7.8 per thousand in the dry season (February), respectively. The delta(13)C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spati…

A Method to Quantitatively Trap Volatilized Organoselenides for Stable Selenium Isotope Analysis

2011

If volatile organoselenides are to be analyzed for their stable Se isotope composition to elucidate sources and formation processes, organoselenides need to be trapped quantitatively to avoid artificial Se isotope fractionation. We developed an efficient trap of organoselenides to be used in microcosms designed to determine the Se isotope fractionation by microbial transformation of inorganic Se to volatile organoselenides. The recoveries of volatilized dimethyldiselenide (DMDSe) from aqueous standard solutions by activated charcoal and alkaline peroxide solution with subsequent freeze-drying and purification via a cation exchange resin were tested. Microcosm experiments with the Se-methyla…

Processing of Generator-Produced 68Ga for Medical Application

2007

The (68)Ge/(68)Ga generator provides an excellent source of positron-emitting (68)Ga. However, newly available "ionic" (68)Ge/(68)Ga radionuclide generators are not necessarily optimized for the synthesis of (68)Ga-labeled radiopharmaceuticals. The eluates have rather large volumes, a high concentration of H(+) (pH of 1), a breakthrough of (68)Ge, increasing with time or frequency of use, and impurities such as stable Zn(II) generated by the decay of (68)Ga, Ti(IV) as a constituent of the column material, and Fe(III) as a general impurity.We have developed an efficient route for the processing of generator-derived (68)Ga eluates, including the labeling and purification of biomolecules. Prec…

Dynamic reaction cell inductively couple plasma-mass spectrometry optimization for seawater analysis

2018

Abstract A direct method for dynamic reaction cell inductively coupled plasma- mass spectrometry (DRC-ICP-MS) trace mineral elements determination in seawater was optimized by Experimental Statistical Design. Five instrumental parameters, such as radiofrequency, sample, nebulizer and reaction gas flows, rejection parameter q and axial field voltage were studied. A Plackett-Burman design was used for screening the most important parameters and the most significant ones were optimized with a Central composite design. Fifteen elements and different isotopes for some of these were considered through the study. The optimization was achieved by using three different reaction gases (NH3, CH4 and O…

Buchbesprechung: Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS) Herausgegeben von Mike Sargent, Chris Harrington…

2003

Accurate determination of element species by on-line coupling of chromatographic systems with ICP-MS using isotope dilution technique

1998

Abstract The instrumental design for coupling different liquid chromatographic systems such as ion, reversed phase, and size exclusion chromatography as well as capillary gas chromatography, with ICP-MS for the determination of element species is described. For accurate analyses obtaining ‘real time’ concentrations of chromatographic peaks, the isotope dilution mass spectrometric (IDMS) technique is applied. Two different spiking modes are possible, one using species-specific and another one using species-unspecific spike solutions of isotope-enriched labelled compounds. The species-specific mode is only possible for element species well defined in their structure and composition, for examp…

Isotope-dilution ICP-MS for trace element determination and speciation: from a reference method to a routine method?

2003

This critical review discusses the conditions under which inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS) is suitable as a routine method for trace element and element-speciation analysis. It can, in general, be concluded that ICP-IDMS has high potential for routine analysis of trace elements if the accuracy of results is of predominant analytical importance. Hyphenated techniques with ICP-IDMS suffer both from lack of commercially available isotope-labeled spike compounds for species-specific isotope dilution and from the more complicated system set-up required for species-unspecific ICP-IDMS analysis. Coupling of gas or liquid chromatography with species-specific …