Incorporation of 15NO2 Nitrogen into Individual Amino Acids by Sunflowers Using Gc-C-Irms |
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Authors: | H.-J. Segschneider D. Hofmann G. Schmidt R. Russow |
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Affiliation: | 1. UFZ-Umweltforschungszentrum Leipzig-Halle GmbH , Leipzig, Deutschland;2. Sektion Bodenforschung , Leipzig;3. Sektion Chemische ?kotoxikologie |
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Abstract: | Abstract The nitrogen isotopic composition of individual amino acids in sunflower leaves after exposures to 15NO2 in the range of ambient NO2 concentrations (5–37 ppb) was analysed by Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS). Amino acids as well as the amides glutamine and asparagine were converted with MTBSTFA (N-methyl-N-(tert.-butyldimethylsilyl)-tri-fluoroacetamid) in pyridine to their corresponding TBDMS derivatives (N, O-tert.-butyldimethylsilyl) in a simple one-step silylation reaction. The derivatized amino acids were separated by gas chromatography, combusted on-line, and the products were sent continuously to an isotope ratio mass spectrometer. Accurate measurements were obtained, when more than 7 nmol N2 were introduced into the ion source of the mass spectrometer per gas chromatographically separated and combusted compound. No interferences of the silicate and fluor containing derivatization agents on the performance of the system were observed. In the range of ambient NO2 concentrations sunflower leaves predominately incorporate the nitrogen derived from atmospheric NO2 into soluble amino acids. The highest δ15N values were measured for alanine. The 15N enrichments of the detectable amino acids increased with increasing 15NO2 concentration. |
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Keywords: | amino acids derivatization GC-C-IRMS MTBSTFA nitrogen 15 nitrogen oxides |
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