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Two new organic reference materials for δ 13 C and δ 15 N measurements and a new value for the δ 13 C of NBS 22 oil
Author(s) -
Qi Haiping,
Coplen Tyler B.,
Geilmann Heike,
Brand Willi A.,
Böhlke J. K.
Publication year - 2003
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.1219
Subject(s) - chemistry , isotopes of nitrogen , isotope analysis , nitrate , carbonate , analytical chemistry (journal) , nitrogen , environmental chemistry , ecology , organic chemistry , biology
Analytical grade L‐glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L‐glutamic acid reference materials with substantially different 13 C and 15 N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L‐glutamic acid and has a δ 13 C value of −26.24‰ relative to VPDB and a δ 15 N value of −4.52‰ relative to N 2 in air. USGS41 was prepared by dissolving analytical grade L‐glutamic acid with L‐glutamic acid enriched in 13 C and 15 N. USGS41 has a δ 13 C value of +37.76‰ and a δ 15 N value of +47.57‰. The δ 13 C and δ 15 N values of both materials were measured against the international reference materials NBS 19 calcium carbonate ( δ 13 C = +1.95‰), L‐SVEC lithium carbonate ( δ 13 C = −46.48‰), IAEA‐N‐1 ammonium sulfate ( δ 15 N = 0.43‰), and USGS32 potassium nitrate ( δ 15 N = 180‰) by on‐line combustion continuous‐flow and off‐line dual‐inlet isotope‐ratio mass spectrometry. Both USGS40 and USGS41 are isotopically homogeneous; reproducibility of δ 13 C is better than 0.13‰, and that of δ 15 N is better than 0.13‰ in 100‐μg amounts. These two isotopic reference materials can be used for (i) calibrating local laboratory reference materials, and (ii) quantifying drift with time, mass‐dependent fractionations, and isotope‐ratio‐scale contraction in the isotopic analysis of various biological materials. Isotopic results presented in this paper yield a δ 13 C value for NBS 22 oil of −29.91‰, in contrast to the commonly accepted value of −29.78‰ for which off‐line blank corrections probably have not been quantified satisfactorily. Published in 2003 by John Wiley & Sons, Ltd.