| Abstract: | 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 13C and 15N 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 ?? 13C value of -26.24??? relative to VPDB and a ?? 15N value of +4.52??? relative to N2 in air. USGS41 was prepared by dissolving analytical grade L-glutamic acid with L-glutamic acid enriched in 13C and 15N. USGS41 has a ?? 13C value of +37.76??? and a ??15N value of +47.57???. The ??13C and ??15N values of both materials were measured against the international reference materials NBS 19 calcium carbonate (??13C = +1.95???), L-SVEC lithium carbonate (??13C = -46.48???), IAEA-N-1 ammonium sulfate (??15N=0.43???), and USGS32 potassium nitrate (?? 15N = 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 ??13C is better than 0.13???, and that of ??15N is better than 0. 13??? in 100-??g 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 ?? 13C 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. |
| Genre: | Article |
| ProdID: | 70025286 |
| Citation Author: | Qi, H.; Coplen, T. B.; Geilmann, H.; Brand, W. A.; Bohlke, J. K. |
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| Citation End Page: | 2487 |
| Citation Issue: | 22 |
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| Citation Language: | English |
| Citation Larger Work Title: | Rapid Communications in Mass Spectrometry |
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| Citation Number Of Pages: | 5 |
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| Citation Search Results Text: | Two new organic reference materials for ??13C and ??15N measurements and a new value for the ?? 13C of NBS 22 oil; 2003; Article; Journal; Rapid Communications in Mass Spectrometry; Qi, H.; Coplen, T. B.; Geilmann, H.; Brand, W. A.; Bohlke, J. K. |
| Citation Start Page: | 2483 |
| Citation Volume: | 17 |
| Citation Year: | 2003 |
| Type: | citation/reference |
| Text: | Two new organic reference materials for ??13C and ??15N measurements and a new value for the ?? 13C of NBS 22 oil; 2003; Article; Journal; Rapid Communications in Mass Spectrometry; Qi, H.; Coplen, T. B.; Geilmann, H.; Brand, W. A.; Bohlke, J. K. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Wed, 1 Jan 2003 00:00 -0600 |
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