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N 2 : a potential pitfall for bulk 2 H isotope analysis of explosives and other nitrogen‐rich compounds by continuous‐flow isotope‐ratio mass spectrometry
Author(s) -
MeierAugenstein Wolfram,
Kemp Helen F.,
Lock Claire M.
Publication year - 2009
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.4112
Subject(s) - chemistry , nitrogen , isotopes of nitrogen , isotope ratio mass spectrometry , mass spectrometry , benzoic acid , analytical chemistry (journal) , nitric acid , isotope analysis , inorganic chemistry , environmental chemistry , chromatography , organic chemistry , ecology , biology
Observations made during the 13 C isotope analysis of gaseous CO 2 in the simultaneous presence of argon in the ion source of the isotope ratio mass spectrometer prompted us to investigate what influence the simultaneous presence of nitrogen would have on both accuracy and precision of bulk 2 H isotope analysis of nitrogen‐rich organic compounds. Initially an international reference material, IAEA‐CH7, was mixed with silver nitrate in various ratios to assess the impact that N 2 evolved from the pyrolysis of nitrogen‐rich organic compounds would have on measured δ 2 H‐values of IAEA‐CH7. In a subsequent experiment, benzoic acid was mixed with silver nitrate to mimic the N:H ratio of organic‐rich nitrogen compounds such as cellulose nitrate and RDX. The results of both experiments showed a significant deterioration of both accuracy and precision for the expected δ 2 H values for IAEA‐CH7 and benzoic acid when model mixtures were converted into hydrogen and nitrogen, and subsequently separated by gas chromatography using standard experimental conditions, namely a 60 cm packed column with molecular sieve 5 Å as stationary phase held at a temperature of 85°C. It was found that bulk 2 H stable isotope analysis of nitrogen‐rich organic compounds employing published standard conditions can result in a loss of accuracy and precision yielding δ 2 H values that are 5 to 25‰ too negative, thus suggesting, for example, that tree‐ring 2 H isotope data based on cellulose nitrate may have to be revised. Copyright © 2009 John Wiley & Sons, Ltd.